visus
/
teensy-audio

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<title>Audio System Design Tool for Teensy Audio Library</title>
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<!-- TODO: generate some or all of this automatically from the C++ source -->

<!-- TODO: add a field for maximum instance count -->
<!-- TODO: add a field for exclusive to other objects (not allowed if they're used) -->
<!-- TODO: add "parameters" fields, to replace the form html stuff -->

<script type="text/javascript">
	RED.nodes.registerType('AudioInputI2S',{
	shortName: "i2s",
		inputs:0,
		outputs:2,
		category: 'input-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioInputI2S">
	<h3>Summary</h3>
	<p>Receive 16 bit stereo audio from the
	<a href="http://www.pjrc.com/store/teensy3_audio.html" target="_blank">audio shield</a>
		or another I2S device, using I2S master mode.</p>
	<p align=center><img src="img/audioshield_inputs.jpg"></p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Left Channel</td></tr>
		<tr class=odd><td align=center>Out 1</td><td>Right Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from the I2S hardware to its 2 output ports.</p>
	<h3>Hardware</h3>
	<p align=center><img src="img/audioshield_backside.jpg"></p>
	<p>The I2S signals are used in "master" mode, where Teensy creates
		all 3 clock signals and controls all data timing.</p>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Pin</th><th>Signal</th><th>Direction</th></tr>
		<tr class=odd><td align=center>9</td><td>BCLK</td><td>Output</td></tr>
		<tr class=odd><td align=center>11</td><td>MCLK</td><td>Output</td></tr>
		<tr class=odd><td align=center>13</td><td>RX</td><td>Input</td></tr>
		<tr class=odd><td align=center>23</td><td>LRCLK</td><td>Output</td></tr>
	</table>
	<p>Audio from
		master mode I2S may be used in the same project as ADC, DAC and
		PWM signals, because all remain in sync to Teensy's timing</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; PassThroughStereo
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Recorder
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; PeakMeterStereo
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; FFT
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; SpectrumAnalyzerBasic
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Chorus
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Flange
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Filter
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Filter_FIR
	</p>
	<h3>Notes</h3>
	<p>Normally, this object is used with the Audio Shield, which
		is controlled separately by the "sgtl5000" object.</p>
	<p>Only one I2S input and one I2S output object may be used.  Master
		and slave modes may not be mixed (both must be of the same type).
	</p>
	<p>I2S master objects can be used together with non-I2S input and output
		objects, for simultaneous audio streaming on different hardware.</p>
</script>
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	<div class="form-row">
		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
		<input type="text" id="node-input-name" placeholder="Name">
	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioInputAnalog',{
	shortName: "adc",
		inputs:0,
		outputs:1,
		category: 'input-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioInputAnalog">
	<h3>Summary</h3>
	<p>Receive audio using the built-in analog to digital converter.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Audio Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from the ADC to its output port.</p>
	<h3>Hardware</h3>
	<p>Pin A2 is used for audio input.  This circuitry is recommended.</p>
	<p align=center><img src="img/adccircuit.png"></p>
	<p>Signal range is 0 to 1.2V</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; PassThroughMono
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; PeakMeterMono
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; DialTone_7segment
	</p>
	<h3>Notes</h3>
	<p>A different pin may be used, but adding it as an parameter
		to the AudioInputAnalog object definition.
	</p>
	<p>For example, to use pin A3:
	</p>
	<p class=desc><span class=keyword>AudioInputAnalog</span>  adc1(<span class=literal>A3</span>);
	</p>

	<p>Noise due to high source impedance, which allows rapidly switching digital signals
		to capacitively couple... avoiding higher analog impedance is the solution.</p>
	<p>Power Supply rejection issue with simple DC bias (bigger capacitor may be needed if 3.3V has low frequency noise)</p>
	<p>Algorithm for automatic DC bias tracking</p>
	<p>TODO: actual noise measurements with different input circuitry
		(it's not as quiet as the audio shield)</p>
</script>
<script type="text/x-red" data-template-name="AudioInputAnalog">
	<div class="form-row">
		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
		<input type="text" id="node-input-name" placeholder="Name">
	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioInputI2Sslave',{
	shortName: "i2ss",
		inputs:0,
		outputs:2,
		category: 'input-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioInputI2Sslave">
	<h3>Summary</h3>
	<p>Receive 16 bit stereo audio from an I2S device using I2S slave mode.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Left Channel</td></tr>
		<tr class=odd><td align=center>Out 1</td><td>Right Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from the I2S hardware to its 2 output ports.</p>
	<h3>Hardware</h3>
	<p>The I2S signals are used in "slave" mode, where the I2S device controls
		data timing.</p>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Pin</th><th>Signal</th><th>Direction</th></tr>
		<tr class=odd><td align=center>9</td><td>BCLK</td><td>Input</td></tr>
		<tr class=odd><td align=center>13</td><td>RX</td><td>Input</td></tr>
		<tr class=odd><td align=center>23</td><td>LRCLK</td><td>Input</td></tr>
	</table>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p>Slave mode I2S <b>should not used in the same project as ADC, DAC and
		PWM</b> signals.  Differences in timing between the I2S device and
		Teensy's clock can cause occasional audio glitches when I2S slave mode
		is used together with other input or output objects based on Teensy's
		timing.</p>
	<p>Only one I2S input and one I2S output object may be used.  Master
		and slave modes may not be mixed (both must be of the same type).
	</p>
</script>
<script type="text/x-red" data-template-name="AudioInputI2Sslave">
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<script type="text/javascript">
	RED.nodes.registerType('AudioOutputI2S',{
	shortName: "i2s",
		inputs:2,
		outputs:0,
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		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioOutputI2S">
	<h3>Summary</h3>
	<p>Transmit 16 bit stereo audio to the
	<a href="http://www.pjrc.com/store/teensy3_audio.html" target="_blank">audio shield</a>
		or another I2S device, using I2S master mode.</p>
	<p align=center><img src="img/audioshield_outputs.jpg"></p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Left Channel</td></tr>
		<tr class=odd><td align=center>In 1</td><td>Right Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from its 2 input ports to the I2S hardware.</p>
	<h3>Hardware</h3>
	<p align=center><img src="img/audioshield_backside.jpg"></p>
	<p>The I2S signals are used in "master" mode, where Teensy creates
		all 3 clock signals and controls all data timing.</p>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Pin</th><th>Signal</th><th>Direction</th></tr>
		<tr class=odd><td align=center>9</td><td>BCLK</td><td>Output</td></tr>
		<tr class=odd><td align=center>11</td><td>MCLK</td><td>Output</td></tr>
		<tr class=odd><td align=center>22</td><td>TX</td><td>Output</td></tr>
		<tr class=odd><td align=center>23</td><td>LRCLK</td><td>Output</td></tr>
	</table>
	<p>Audio from
		master mode I2S may be used in the same project as ADC, DAC and
		PWM signals, because all remain in sync to Teensy's timing</p>
	<h3>Examples</h3>
	<p>Nearly all the examples use this object.  Here are some of the highlights:</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; PassThroughStereo
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; SamplePlayer
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Recorder
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; WavFilePlayer
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Chorus
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Synthesis &gt; PlaySynthMusic
	</p>
	<h3>Notes</h3>
	<p>Normally, this object is used with the Audio Shield, which
		is controlled separately by the "sgtl5000" object.</p>
	<p>Only one I2S input and one I2S output object may be used.  Master
		and slave modes may not be mixed (both must be of the same type).
	</p>
</script>
<script type="text/x-red" data-template-name="AudioOutputI2S">
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<script type="text/javascript">
	RED.nodes.registerType('AudioOutputSPDIF',{
	shortName: "spdif",
		inputs:2,
		outputs:0,
		category: 'output-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioOutputSPDIF">
	<h3>Summary</h3>
	<p>Transmit 16 bit stereo audio as Digital S/PDIF.</p>
	<p align=center><img src="img/spdif_proto.jpg"></p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Left Channel</td></tr>
		<tr class=odd><td align=center>In 1</td><td>Right Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from its 2 input ports S/PDIF encoded digital
		audio on pin 22.</p>
	<h3>Hardware</h3>
	<p>The S/PDIF output signal can be used to drive an optical TOSLINK
		cable, or a standard (usually orange) RCA jack.</p>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Pin</th><th>Signal</th><th>Direction</th></tr>
		<tr class=odd><td align=center>22</td><td>S/PDIF</td><td>Output</td></tr>
	</table>
	<p>For optical TOSLINK output, this
		<a href="https://www.oshpark.com/shared_projects/KcDBKHta" target="_blank">OSH Park board</a>
		can be used with the inexpensive Everlight PLT133/T6A connector, available
		at Digikey, 1080-1434-ND.
		</p>
	<h3>Examples</h3>
	<p>The AudioOutputSPDIF object can be used in place of the AudioOutputI2S object,
	<p>used in nearly all the examples.  The WavFilePlayer shows how to substitute
		output objects for different hardware types.
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; WavFilePlayer
	</p>
	<h3>Credits</h3>
	<p><a href="https://github.com/FrankBoesing" target="_blank">Frank Boesing</a>
		developed the AudioOutputSPDIF code.  The original
		<a href="https://forum.pjrc.com/threads/28639-S-pdif" target="_blank">forum disussion</a>
		included valuable input and code from "kpc".
	<h3>Notes</h3>
	<p>S/PDIF output uses the I2S hardware.  This object can not be used
		together with any of the I2S objects, because it requires the I2S
		hardware with different internal settings.</p>
	</p>
</script>
<script type="text/x-red" data-template-name="AudioOutputSPDIF">
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	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioOutputAnalog',{
	shortName: "dac",
		inputs:1,
		outputs:0,
		category: 'output-function',
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioOutputAnalog">
	<h3>Summary</h3>
	<p>Transmit 12 bit audio using Teensy 3.1's built-in digital to analog converter.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Audio Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from the ADC to its output port.</p>
	<h3>Hardware</h3>
	<p align=center><img src="img/dacpin.jpg"></p>
	<p>Signal range is 0 to 1.2V</p>
	<p>Most applications require at least a 10&micro;F DC-blocking capacitor.</p>
	<p>TODO: photo of Teensy 3.1 with 10&micro;F capacitor and 3.5mm jack.</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; PassThroughMono
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; SamplePlayer
	</p>
	<h3>Notes</h3>
	<p>The output rate is 44.1 kHz (no oversampling).  Ultrasonic noise present if
		not filtered.  This may not
		be an issue for many uses, but care should be used if amplified and driven
		to high power tweeters.</p>
</script>
<script type="text/x-red" data-template-name="AudioOutputAnalog">
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<script type="text/javascript">
	RED.nodes.registerType('AudioOutputPWM',{
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		inputs:1,
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioOutputPWM">
	<h3>Summary</h3>
	<p>Transmit audio using Teensy 3.1's PWM pins.  Two pins are
		used for coarse and fine pulses, to be combined by scaled
		resistors.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Audio Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from the its input port to the PWM pins.</p>
	<h3>Hardware</h3>
	<p>The following circuit is recommended.</p>
	<p align=center><img src="img/pwmdualcircuit.jpg"></p>
	<p>Signal range is approx 1.55 Vp-p.</p>
	<p>These resistor values assume approx 20 ohms output impedance
		on the digital pins.  The 127K resistor may be adjusted or
		trimmed for variation in output drive and tolerance on the
		475 ohm resistor.</p>
	<p>A plastic film (Polypropylene, Polyethylene, Polyester, etc) or
		C0G/NPO ceramic capacitor should be used for filtering.  Low
		quality ceramic (X7R, Y5V, Z5U, etc) can cause signal distortion.</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; PassThroughMono
	</p>
	<h3>Notes</h3>
	<p>This object only works properly when Tools > CPU_Speed is set to
		48 or 96 MHz.  Other speeds aren't supported and will likely fail
		in strange ways.</p>
	<p>The PWM carrier frequency is 88.2 kHz.  The suggested circuit
		will only slightly filter the carrier.  Extra filtering will be
		required for a clean signal without the ultrasonic PWM carrier.
		</p>
	<p>Analog signals created by filtering PWM waveforms use the digital
		power supply as their reference voltage.  Any noise on the digital
		power line can directly couple to the output signal.  The built-in DAC or
		<a href="http://www.pjrc.com/store/teensy3_audio.html" target="_blank">audio shield</a>
		should be used when higher quality signals are needed.</p>
</script>
<script type="text/x-red" data-template-name="AudioOutputPWM">
	<div class="form-row">
		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
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	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioOutputI2Sslave',{
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		inputs:2,
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		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioOutputI2Sslave">
	<h3>Summary</h3>
	<p>Transmit 16 bit stereo audio to an I2S device using I2S slave mode.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Left Channel</td></tr>
		<tr class=odd><td align=center>In 1</td><td>Right Channel</td></tr>
	</table>
	<h3>Functions</h3>
	<p>This object has no functions to call from the Arduino sketch.  It
		simply streams data from its 2 input ports to the I2S hardware.</p>
	<h3>Hardware</h3>
	<p>The I2S signals are used in "slave" mode, where the I2S device controls
		data timing.</p>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Pin</th><th>Signal</th><th>Direction</th></tr>
		<tr class=odd><td align=center>9</td><td>BCLK</td><td>Input</td></tr>
		<tr class=odd><td align=center>22</td><td>TX</td><td>Output</td></tr>
		<tr class=odd><td align=center>23</td><td>LRCLK</td><td>Input</td></tr>
	</table>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; WM8731MikroSine
	</p>
	<h3>Notes</h3>
	<p>Slave mode I2S <b>should not used in the same project as ADC, DAC and
		PWM</b> signals.  Differences in timing between the I2S device and
		Teensy's clock can cause occasional audio glitches when I2S slave mode
		is used together with other input or output objects based on Teensy's
		timing.</p>
	<p>Only one I2S input and one I2S output object may be used.  Master
		and slave modes may not be mixed (both must be of the same type).
	</p>
</script>
<script type="text/x-red" data-template-name="AudioOutputI2Sslave">
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</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioMixer4',{
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioMixer4">
	<h3>Summary</h3>
	<p>Combine up to 4 audio signals together, each with adjustable gain.
		All channels support signal attenuation or amplification.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Input signal #1</td></tr>
		<tr class=odd><td align=center>In 1</td><td>Input signal #2</td></tr>
		<tr class=odd><td align=center>In 2</td><td>Input signal #3</td></tr>
		<tr class=odd><td align=center>In 3</td><td>Input signal #4</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Sum of all inputs</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>gain</span>(channel, level);</p>
	<p class=desc>Adjust the amplification or attenuation.  "channel" must
		be 0 to 3.  "level" may be any floating point number from 0 to 32767.
		1.0 passes the signal through directly.  Level of 0 shuts the channel
		off completely.  Between 0 to 1.0 attenuates the signal, and above
		1.0 amplifies it.  All 4 channels have separate settings.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; SamplePlayer
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Synthesis &gt; PlaySynthMusic
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; SpectrumAnalyzerBasic
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; DialTone_Serial
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; MemoryAndCpuUsage
	</p>
	<h3>Notes</h3>
	<p>Signal clipping can occur when any channel has gain greater than 1.0,
		or when multiple signals add together to greater than 1.0.</p>
	<p>More than 4 channels may be combined by connecting multiple mixers
		in tandem.  For example, a 16 channel mixer may be built using 5
		mixers, where the fifth mixer combines the outputs of the first 4.
	</p>
</script>
<script type="text/x-red" data-template-name="AudioMixer4">
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<script type="text/javascript">
	RED.nodes.registerType('AudioPlayMemory',{
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		inputs:0,
		outputs:1,
		category: 'play-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioPlayMemory">
	<h3>Summary</h3>
	<p>Play a short sound clip, stored directly in memory.
		Data files are created with the
		<a href="https://github.com/PaulStoffregen/Audio/tree/master/examples/SamplePlayer/wav2sketch" target="_blank">wav2sketch program</a>,
		and copied to the sketch folder to become part of your sketch.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Sound Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>play</span>(data);</p>
	<p class=desc>Begin playing a sound clip.  If already playing, the
		currently playing clip is stopped and this new data begins
		playing from the beginning.
	</p>
	<p class=func><span class=keyword>stop</span>();</p>
	<p class=desc>Stop playing.  If not playing, this function has no effect.
	</p>
	<p class=func><span class=keyword>isPlaying</span>();</p>
	<p class=desc>Return true (non-zero) if playing, or false (zero)
		when not playing.
	</p>
	<p class=func><span class=keyword>positionMillis</span>();</p>
	<p class=desc>While playing, return the current time offset, in
		milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<p class=func><span class=keyword>lengthMillis</span>();</p>
	<p class=desc>Return the total length of the current sound clip,
		in milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; SamplePlayer
	</p>
	<h3>Notes</h3>
	<p>TODO: supported sample rates: 11.025, 22.05, 44.1</p>
	<p>TODO: ulaw vs uncompressed encoding</p>
	<p>Polyphonic playback can be built by creating multiple
		objects, with their output combined by mixers.</p>
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<script type="text/x-red" data-template-name="AudioPlayMemory">
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</script>


<script type="text/javascript">
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioPlaySdWav">
	<h3>Summary</h3>
	<p>Play a WAV file, stored on a SD card.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Left Channel Output</td></tr>
		<tr class=odd><td align=center>Out 1</td><td>Right Channel Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>play</span>(filename);</p>
	<p class=desc>Begin playing a WAV file.  If a file is already playing,
		it is stopped and this file starts playing from the beginning.
	</p>
	<p class=func><span class=keyword>stop</span>();</p>
	<p class=desc>Stop playing.  If not playing, this function has no effect.
	</p>
	<p class=func><span class=keyword>isPlaying</span>();</p>
	<p class=desc>Return true (non-zero) if playing, or false (zero)
		when not playing.  See the note below about delayed start.
	</p>
	<p class=func><span class=keyword>positionMillis</span>();</p>
	<p class=desc>While playing, return the current time offset, in
		milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<p class=func><span class=keyword>lengthMillis</span>();</p>
	<p class=desc>Return the total length of the current sound clip,
		in milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; WavFilePlayer
	</p>
	<h3>Notes</h3>
	<p>Only 16 bit PCM, 44100 Hz WAV files are supported.  When mono
		files are played, both output ports transmit a copy of the
		single sound.  Of course, stereo WAV files play with the left
		channel on port 0 and the right channel on port 1.
	</p>
	<p>A brief delay after calling play() will usually occur before
		isPlaying() returns true and positionMillis() returns valid
		time offset.  WAV files have a header at the beginning of the
		file, which the audio library must read and parse before
		playing can begin.
	</p>
	<p>While playing, the audio library accesses the SD card automatically.
		If card access is required, you must
		<a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html" target="_blank">use AudioNoInterrupts()</a>
		to prevent the library from accessing the SD card while you use it.
		Disabling the audio library interrupt for too long may cause audible
		dropouts or glitches.
	</p>
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<script type="text/javascript">
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioPlaySdRaw">
	<h3>Summary</h3>
	<p>Play a RAW data file, stored on a SD card.  RAW format is simpler
		than WAV and begins playing immediately, without parsing WAV file
		header info.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Sound Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>play</span>(filename);</p>
	<p class=desc>Begin playing a RAW data file.  If a file is already playing,
		it is stopped and this file starts playing from the beginning.
	</p>
	<p class=func><span class=keyword>stop</span>();</p>
	<p class=desc>Stop playing.  If not playing, this function has no effect.
	</p>
	<p class=func><span class=keyword>isPlaying</span>();</p>
	<p class=desc>Return true (non-zero) if playing, or false (zero)
		when not playing.
	</p>
	<p class=func><span class=keyword>positionMillis</span>();</p>
	<p class=desc>While playing, return the current time offset, in
		milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<p class=func><span class=keyword>lengthMillis</span>();</p>
	<p class=desc>Return the total length of the current sound clip,
		in milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Recorder
	</p>
	<h3>Notes</h3>
	<p>The data file must be RAW 16 bit signed integers in LSB-first format.
	</p>
	<p>While playing, the audio library accesses the SD card automatically.
		If card access is required, you must
		<a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html" target="_blank">AudioNoInterrupts()</a>
		to prevent the library from accessing the SD card while you use it.
		Disabling the audio library interrupt for too long may cause audible
		dropouts or glitches.
	</p>
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<script type="text/x-red" data-template-name="AudioPlaySdRaw">
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</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioPlaySerialflashRaw',{
	shortName: "playFlashRaw",
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		outputs:1,
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		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioPlaySerialflashRaw">
	<h3>Summary</h3>
	<div>
	<p>Play a RAW data file, stored on a Serial Flash chip.  These chips
		are far more efficient than SD cards, allowing many files to be
		played simultaneously by copies of this object.
		</p>
	<p align=center><img src="img/w25q128fv.jpg"><br><small>W25Q128FV Serial Flash</small></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Sound Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>play</span>(filename);</p>
	<p class=desc>Begin playing a RAW data file.  If a file is already playing,
		it is stopped and this file starts playing from the beginning.
	</p>
	<p class=func><span class=keyword>stop</span>();</p>
	<p class=desc>Stop playing.  If not playing, this function has no effect.
	</p>
	<p class=func><span class=keyword>isPlaying</span>();</p>
	<p class=desc>Return true (non-zero) if playing, or false (zero)
		when not playing.
	</p>
	<p class=func><span class=keyword>positionMillis</span>();</p>
	<p class=desc>While playing, return the current time offset, in
		milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<p class=func><span class=keyword>lengthMillis</span>();</p>
	<p class=desc>Return the total length of the current sound clip,
		in milliseconds.  When not playing, the return from this function
		is undefined.
	</p>
	<h3>Examples</h3>
	<!--<p class=exam>File &gt; Examples &gt; Audio &gt; Recorder-->
	<p class=exam>TODO: play example needed....
	</p>
	<p class=exam>File &gt; Examples &gt; SerialFlash &gt; CopyFromSD
	</p>
	<h3>Notes</h3>
	<p>The data file must be RAW 16 bit signed integers in LSB-first format.
	</p>
	<p>The <a href="https://github.com/PaulStoffregen/SerialFlash" target="_blank">SerialFlash library</a>
		is used to access the flash chip.  You can also use SerialFlash's functions
		to access the stored files, or add data to the flash chip.
	</p>
	<p>File names are case sensitive with SerialFlash.  If your sound does
		not play, use <b>File &gt; Examples &gt; SerialFlash &gt; ListFiles</b> to
		check the exact file names stored in the flash memory chip.
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<script type="text/javascript">
	RED.nodes.registerType('AudioPlayQueue',{
	shortName: "queue",
		inputs:0,
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		icon: "arrow-in.png"
	});
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<script type="text/x-red" data-help-name="AudioPlayQueue">
	<h3>Summary</h3>
	<p>Play audio data provided by the Arduino sketch.  This object provides
		functions to allow the sketch code to push data into the audio system.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Sound Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>play</span>(int16);</p>
	<p class=desc>not yet implemented
	</p>
	<p class=func><span class=keyword>play</span>(int16[], length);</p>
	<p class=desc>not yet implemented
	</p>
	<p class=func><span class=keyword>getBuffer</span>();</p>
	<p class=desc>Returns a pointer to an array of 128 int16.  This buffer
		is within the audio library memory pool, providing the most efficient
		way to input data to the audio system.  The buffer is likely to be
		populated by previously used data, so the entire 128 words should be
		written before calling playBuffer().  Only a single buffer should be
		requested at a time.  This function may return NULL if no memory is
		available.
	</p>
	<p class=func><span class=keyword>playBuffer</span>();</p>
	<p class=desc>Transmit the buffer previously obtained from getBuffer().
	</p>
	<h3>Examples</h3>
		<p><a href="http://community.arm.com/groups/embedded/blog/2014/05/23/led-video-panel-at-maker-faire-2014" target="_blank">4320 LED Video+Sound Project</a>
		</p>
	<!--<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p>TODO: many caveats....</p>
	<p>
	</p>
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<script type="text/javascript">
	RED.nodes.registerType('AudioRecordQueue',{
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		outputs:0,
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		icon: "arrow-in.png"
	});
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<script type="text/x-red" data-help-name="AudioRecordQueue">
	<h3>Summary</h3>
	<p>Record audio data by sending to the Arduino sketch.  This object allows
		sketch code to receive audio packets.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Sound To Access</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>begin</span>();</p>
	<p class=desc>Begin capturing incoming audio to the queue.  After calling
		begin, readBuffer() and freeBuffer(), or clear() must be used frequently
		to prevent the queue from filling up.
	</p>
	<p class=func><span class=keyword>available</span>();</p>
	<p class=desc>Returns the number of audio packets available to read.
	</p>
	<p class=func><span class=keyword>readBuffer</span>();</p>
	<p class=desc>Read a single audio packet.  A pointer to a 128 sample
		array of 16 bit integers is returned.  NULL is returned if no packets
		are available.
	</p>
	<p class=func><span class=keyword>freeBuffer</span>();</p>
	<p class=desc>Release the memory from the previously read packet returned
		from readBuffer().  Only a single packet at a time may be read, and
		each packet must be freed with this function, to return the memory to
		the audio library.
	</p>
	<p class=func><span class=keyword>clear</span>();</p>
	<p class=desc>Discard all audio held in the queue.
	</p>
	<p class=func><span class=keyword>end</span>();</p>
	<p class=desc>Stop capturing incoming audio into the queue.  Data already
		captured remains in the queue and may be read with readBuffer().
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Recorder
	</p>
	<h3>Notes</h3>
	<p>
		Up to 52 packets may be queued by this object, which allows approximately
		150 ms of audio to be held in the queue, to allow time for the Arduino
		sketch to write data to media or do other high-latency tasks.

The actual packets are taken
		from the pool created by AudioMemory().
	</p>
</script>
<script type="text/x-red" data-template-name="AudioRecordQueue">
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</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioSynthWaveformSine',{
	shortName: "sine",
		inputs:0,
		outputs:1,
		category: 'synth-function',
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioSynthWaveformSine">
	<h3>Summary</h3>
	<p>Create a sine wave signal</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Sine Wave Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>amplitude</span>(level);</p>
	<p class=desc>Set the amplitude, from 0 to 1.0.
	</p>
	<p class=func><span class=keyword>frequency</span>(freq);</p>
	<p class=desc>Set the frequency, from 0 to 22000.  Very low values may
		be used to create a LFO (Low Frequency Oscillator) for objects
		with modulation signal inputs.
	</p>
	<p class=func><span class=keyword>phase</span>(angle);</p>
	<p class=desc>
		Cause the generated waveform to jump to a specific point within
		its cycle.  Angle is from 0 to 360 degrees.  When multiple objects
		are configured,
		<a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html" target="_blank">AudioNoInterrupts()</a>
		should be used to guarantee all new settings take effect together.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; MemoryAndCpuUsage
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; DialTone_Serial
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; FFT
	</p>
	<h3>Notes</h3>
	<p></p>
</script>
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<script type="text/javascript">
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioSynthWaveformSineModulated">
	<h3>Summary</h3>
	<p>Create a modulated sine wave, using any audio signal to continuously
		modulate the sine wave frequency.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Modulation Signal</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Sine Wave Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>amplitude</span>(level);</p>
	<p class=desc>Set the amplitude, from 0 to 1.0.
	</p>
	<p class=func><span class=keyword>frequency</span>(freq);</p>
	<p class=desc>Set the center frequency, from 0 to 11000.  The output will
		be this center frequency when the input modulation signal is zero.
		Modulation input 1.0 causes the frequency to double, and input -1.0
		causes zero Hz (DC) output.  For less modulation, attenuate the input
		signal (perhaps with a mixer object) before it arrives here.
	</p>
	<p class=func><span class=keyword>phase</span>(angle);</p>
	<p class=desc>
		Cause the generated waveform to jump to a specific point within
		its cycle.  Angle is from 0 to 360 degrees.  When multiple objects
		are configured,
		<a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html" target="_blank">AudioNoInterrupts()</a>
		should be used to guarantee all new settings take effect together.
	</p>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p></p>
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<script type="text/javascript">
	RED.nodes.registerType('AudioSynthWaveform',{
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioSynthWaveform">
	<h3>Summary</h3>
	<p>Create a waveform: sine, sawtooth, square, triangle, pulse or arbitrary.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Waveform Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>begin</span>(waveform);</p>
	<p class=desc>Configure the waveform type to create.
	</p>
	<p class=func><span class=keyword>begin</span>(level, frequency, waveform);</p>
	<p class=desc>Output a waveform, and set the amplitude and frequency.
	</p>
	<p class=func><span class=keyword>frequency</span>(freq);</p>
	<p class=desc>Change the frequency.
	</p>
	<p class=func><span class=keyword>amplitude</span>(level);</p>
	<p class=desc>Change the amplitude.  Set to 0 to turn the signal off.
	</p>
	<p class=func><span class=keyword>phase</span>(angle);</p>
	<p class=desc>
		Cause the generated waveform to jump to a specific point within
		its cycle.  Angle is from 0 to 360 degrees.  When multiple objects
		are configured,
		<a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html" target="_blank">AudioNoInterrupts()</a>
		should be used to guarantee all new settings take effect together.
	</p>
	<p class=func><span class=keyword>pulseWidth</span>(amount);</p>
	<p class=desc>Change the width (duty cycle) of the pulse.</p>
	<p class=func><span class=keyword>arbitraryWaveform</span>(array, maxFreq);</p>
	<p class=desc>
		Configure the waveform to be used with WAVEFORM_ARBITRARY.  Array
		must be an array of 256 samples.  Currently, the data is used
		without any filtering, which can cause aliasing with frequencies
		above 172 Hz.  For higher frequency output, you must bandwidth
		limit your waveform data.  Someday, "maxFreq" will be used to
		do this automatically.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Synthesis &gt; PlaySynthMusic
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Synthesis &gt; pulseWidth
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; WM8731MikroSine
	</p>
	<h3>Notes</h3>
	<p>Supported Waveforms:<br>
		<ul>
		<li><span class=literal>WAVEFORM_SINE</span></li>
		<li><span class=literal>WAVEFORM_SAWTOOTH</span></li>
		<li><span class=literal>WAVEFORM_SQUARE</span></li>
		<li><span class=literal>WAVEFORM_TRIANGLE</span></li>
		<li><span class=literal>WAVEFORM_ARBITRARY</span></li>
		<li><span class=literal>WAVEFORM_PULSE</span></li>
		</ul>
	</p>
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<script type="text/javascript">
	RED.nodes.registerType('AudioSynthToneSweep',{
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		outputs:1,
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		icon: "arrow-in.png"
	});
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<script type="text/x-red" data-help-name="AudioSynthToneSweep">
	<h3>Summary</h3>
	<p>Create a continuously varying (in frequency) sine wave</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Continuously varying tone</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>play</span>(level, lowFreq, highFreq, time);</p>
	<p class=desc>Start generating frequency sweep output.  The time is specified
		in milliseconds.  Level is 0 to 1.0.
	</p>
	<p class=func><span class=keyword>isPlaying</span>();</p>
	<p class=desc>Returns true (non-zero) while the output is active.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; ToneSweep
	</p>
	<h3>Notes</h3>
	<p>Uses excessive CPU time</p>
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<script type="text/javascript">
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	});
</script>
<script type="text/x-red" data-help-name="AudioSynthWaveformDc">
	<h3>Summary</h3>
	<p>Create constant (DC) signal, useful for control of objects that take
		a modulation or control input signal.  This constant level can be
		used to modify other waveforms using mixer or multiplier objects</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Output constant DC level</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>amplitude</span>(level);</p>
	<p class=desc>Set the output.  Level is -1.0 to 1.0.  The output is
		changed immediately.
	</p>
	<p class=func><span class=keyword>amplitude</span>(level, milliseconds);</p>
	<p class=desc>Set the output.  Level is -1.0 to 1.0.  The output is
		gradually changed over a "milliseconds" time period.  Any time may
		be specified, but periods longer than 1 second may be automatically
		shortened for small level changes, due to numerical precision limits.
	</p>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p>Of course, the term "DC", for Direct Current, doesn't properly apply
		to a pure digital stream of numerical values.  But the term is widely
		understood in audio applications, so hopefully it's not too confusing?</p>
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<script type="text/javascript">
	RED.nodes.registerType('AudioSynthNoiseWhite',{
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioSynthNoiseWhite">
	<h3>Summary</h3>
	<div>
	<p>Create white noise.
		</p>
	<p align=center><img src="img/whitenoise.png"></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>White Noise</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>amplitude</span>(level);</p>
	<p class=desc>Set the output peak level, from 0 (off) to 1.0.
		The default is off.  Noise is generated only after setting
		to a non-zero level.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>
	<h3>Notes</h3>
	<p>Setting the amplitude to zero causes this object to stop using
		CPU time to generate random numbers.
	</p>
</script>
<script type="text/x-red" data-template-name="AudioSynthNoiseWhite">
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		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
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<script type="text/javascript">
	RED.nodes.registerType('AudioSynthNoisePink',{
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	});
</script>
<script type="text/x-red" data-help-name="AudioSynthNoisePink">
	<h3>Summary</h3>
	<div>
	<p>Create pink noise, using Stefan Stenzel's "New Shade Of Pink" algorithm.
		</p>
	<!--<p align=center><img src="img/whitenoise.png"></p>-->
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>Out 0</td><td>Pink Noise</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>amplitude</span>(level);</p>
	<p class=desc>Set the output peak level, from 0 (off) to 1.0.
		The default is off.  Noise is generated only after setting
		to a non-zero level.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; MemoryAndCpuUsage
	</p>
	<h3>Notes</h3>
	<p>Setting the amplitude to zero causes this object to stop using
		CPU time.  CPU usage is approx 3% on Teensy 3.1.
	</p>
	<p>Stefan Stenzel's
		<a href="http://stenzel.waldorfmusic.de/post/pink/" target="_blank">New Shade Of Pink</a>
		algorithm.  Stefan's terms of use are "Use for any purpose. If used
		in a commercial product, you should give me one."
	</p>
</script>
<script type="text/x-red" data-template-name="AudioSynthNoisePink">
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		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
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	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioEffectFade',{
	shortName: "fade",
		inputs:1,
		outputs:1,
		category: 'effect-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioEffectFade">
	<h3>Summary</h3>
	<p>Gradually increase or decrease audio level.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal Input</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Signal Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>fadeIn</span>(milliseconds);</p>
	<p class=desc>Begin increasing the audio level, to reach 1.0 (input passed
		directly to the output) after "milliseconds" time.
	</p>
	<p class=func><span class=keyword>fadeOut</span>(milliseconds);</p>
	<p class=desc>Begin decreasing the audio level, to reach 0 (no output)
		after "milliseconds" time.
	</p>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p>Cross fading can be built with 2 fade objects fed into a mixer.
		When one fade object is off (fully faded out) and the other on
		(fully faded in), if both are started at the same moment for the
		same time duration, their signal gains always add to 1.0.  This
		allows 2 fade objects to work together for a smooth transition
		between a pair of signals.
	</p>
	<p><a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html" target="_blank">AudioNoInterrupts()</a>
		should be used when changing
		settings on multiple objects, so all changes always take effect
		at the same moment.
	</p>
</script>
<script type="text/x-red" data-template-name="AudioEffectFade">
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<script type="text/javascript">
	RED.nodes.registerType('AudioEffectChorus',{
	shortName: "chorus",
		inputs:1,
		outputs:1,
		category: 'effect-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioEffectChorus">
<h3>Summary</h3>
	<p>The chorus effect simulates the richness of several nearly-identical
	sound sources (like the way a choir sounds different to a single singer).
	It does this by sampling from a delay line, so each voice is actually
	the same but at a slightly different point in time. This is a type of
	comb filtering.</p>
	<p>Chorus combines one or more samples ranging from the most recent
	sample back to about 50ms ago. The additional samples are evenly spread
	through the supplied delay line, and there is no modulation.</p>
	<p>If the number of voices is specified as 2, then the
	effect combines the current sample and the oldest sample (the last one
	in the delay line). If the number of voices is 3 then the effect combines
	the most recent sample, the oldest sample and the sample in the middle of
	the delay line.</p>
	<p>For two voices the effect can be represented as:<br/>
	result = (sample(0) + sample(dt))/2<br/>
	where sample(0) represents the current sample and sample(dt)
	is the sample in the delay line from dt milliseconds ago.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class="top"><th>Port</th><th>Purpose</th></tr>
		<tr class="odd"><td align="center">In 0</td><td>Signal Input</td></tr>
		<tr class="odd"><td align="center">Out 0</td><td>Chorused Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>begin</span>(delayBuffer, length, n_chorus);</p>
	<p class=desc>Create a chorus by specifying the address of the delayline, the
	total number of samples in the delay line (often done as an integer multiple of
	AUDIO_BLOCK_SAMPLES) and the number of voices in the chorus <em>including</em>
	the original voice (so, 2 and up to get a chorus effect, although you can
	specify 1 if you want).
	</p>
	<p class=func><span class=keyword>modify</span>(n_chorus);</p>
	<p class=desc>Alters the number of voices in a running chorus (previously started with begin).
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Chorus
	</p>
	<h3>Notes</h3>
	<p>The longer the length of the chorus, the more memory blocks are used.</p>
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<script type="text/javascript">
	RED.nodes.registerType('AudioEffectFlange',{
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		inputs:1,
		outputs:1,
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		color:"#E6E0F8",
		icon: "arrow-in.png"
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<script type="text/x-red" data-help-name="AudioEffectFlange">
<h3>Summary</h3>
	<p>Originally, flanging was produced by playing the same signal on two synchronized
	reel-to-reel tape recorders and making one of the reels slow down and speed up by
	pressing on the flange of the reel (hence the name). This is a type of
	comb filtering, and produces a harmonically-related series of peaks and notches
	in the audio spectrum.</p>
	<p>This flanger uses a delay line, combining the original voice with only one sample from the delay
	line, but the position of that sample varies sinusoidally.</p>
	<p>The effect can be represented as:<br>
	result = sample(0) + sample(dt + depth*sin(2*PI*Fe))</p>
	<p>The value of the sine function is always a number from -1 to +1 and
	so the result of depth*(sin(Fe)) is always a number from -depth to +depth.
	Thus, the delayed sample will be selected from the range (dt-depth) to
	(dt+depth). This selection will vary at whatever rate is specified as the
	frequency of the effect, Fe. Typically a low frequency (a few Hertz) is used.
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class="top"><th>Port</th><th>Purpose</th></tr>
		<tr class="odd"><td align="center">In 0</td><td>Signal Input</td></tr>
		<tr class="odd"><td align="center">Out 0</td><td>Flanged Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>begin</span>(delayBuffer, length, offset, depth, delayRate);</p>
	<p class=desc>Create a flanger by specifying the address of the delayline, the
	total number of samples in the delay line (often done as an integer multiple of
	AUDIO_BLOCK_SAMPLES), the offset (how far back the flanged sample is from the original voice),
	the modulation depth (larger values give a greater variation) and the modulation
	frequency, in Hertz.
	</p>
	<p class=func><span class=keyword>modify</span>(offset, depth, delayRate);</p>
	<p class=desc>Alters the parameters in a running flanger (previously started with begin).
	</p>

	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Flange
	</p>
	<h3>Notes</h3>
	<p>The longer the length of the delay buffer, the more memory blocks are used.</p>
	<p>Try these settings:<br>
#define FLANGE_DELAY_LENGTH (2*AUDIO_BLOCK_SAMPLES)<br>
and<br>
int s_idx = 2*FLANGE_DELAY_LENGTH/4;<br>
int s_depth = FLANGE_DELAY_LENGTH/4;<br>
double s_freq = 3;</p>
<p>The flange effect can also produce a chorus-like effect if a longer
delay line is used with a slower modulation rate, for example try:<br>
#define FLANGE_DELAY_LENGTH (12*AUDIO_BLOCK_SAMPLES)<br>
and<br>
int s_idx = 3*FLANGE_DELAY_LENGTH/4;<br>
int s_depth = FLANGE_DELAY_LENGTH/8;<br>
double s_freq = .0625;</p>
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<script type="text/x-red" data-template-name="AudioEffectFlange">
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<script type="text/javascript">
	RED.nodes.registerType('AudioEffectEnvelope',{
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		icon: "arrow-in.png"
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<script type="text/x-red" data-help-name="AudioEffectEnvelope">
	<h3>Summary</h3>
	<div>
	<p>Modify a signal with a DAHDSR (Delay Attack Hold Decay Sustain
		Release) envelope.
	</p>
	<p align=center><img src="img/dahdsr.png"></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal Input</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Signal with Envelope Applied</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>noteOn</span>();</p>
	<p class=desc>Begin the delay to attack, or the attack phase is
		delay is zero.
	</p>
	<p class=func><span class=keyword>noteOff</span>();</p>
	<p class=desc>Begin the release phase.
	</p>
	<p class=func><span class=keyword>delay</span>(milliseconds);</p>
	<p class=desc>Set the delay from noteOn to the attach phase.  The
		default is zero, for no delay.
	</p>
	<p class=func><span class=keyword>attack</span>(milliseconds);</p>
	<p class=desc>Set the attack time.  The default is 1.5 milliseconds.
	</p>
	<p class=func><span class=keyword>hold</span>(milliseconds);</p>
	<p class=desc>Set the hold time.  The default is 0.5 milliseconds.
	</p>
	<p class=func><span class=keyword>decay</span>(milliseconds);</p>
	<p class=desc>Set the decay time.  The default is 15 milliseconds.
	</p>
	<p class=func><span class=keyword>sustain</span>(level);</p>
	<p class=desc>Set the sustain level.  The range is 0 to 1.0.  The
		gain will be maintained at this level after the decay phase,
		until noteOff() is called.
	</p>
	<p class=func><span class=keyword>release</span>(milliseconds);</p>
	<p class=desc>Set the release time.  The default is 30 millisecond.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Synthesis &gt; PlaySynthMusic
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Synthesis &gt; pulseWidth
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; MemoryAndCpuUsage
	</p>
	<h3>Notes</h3>
	<p>To achieve the more common ADSR shape, simply
        set delay and hold to zero.</p>
	<p>The recommended range for each of the 5 timing inputs is 0 to 50
		milliseconds.  Up to 200 ms can be used, with somewhat reduced
		accuracy</p>
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<script type="text/x-red" data-template-name="AudioEffectEnvelope">
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<script type="text/javascript">
	RED.nodes.registerType('AudioEffectMultiply',{
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		inputs:2,
		outputs:1,
		category: 'effect-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
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<script type="text/x-red" data-help-name="AudioEffectMultiply">
	<h3>Summary</h3>
	<div>
	<p>Multiply two signals together, useful for amplitude modulation
		or "voltage controlled amplification".
	</p>
	<p align=center><img src="img/multiply.png"><br><small>56 Hz and 1 kHz sine waves multiplied.</small></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal Input</td></tr>
		<tr class=odd><td align=center>In 1</td><td>Signal Input</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Signal with Envelope Applied</td></tr>
	</table>
	<h3>Functions</h3>
	<p>There are no functions to call from the Arduino sketch.
		This object simply multiplies the 2 signals to create
		a continuous output
	</p>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p>
    </p>
</script>
<script type="text/x-red" data-template-name="AudioEffectMultiply">
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<script type="text/javascript">
	RED.nodes.registerType('AudioEffectDelay',{
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		outputs:8,
		category: 'effect-function',
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		icon: "arrow-in.png"
	});
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<script type="text/x-red" data-help-name="AudioEffectDelay">
	<h3>Summary</h3>
	<div>
	<p>Delay a signal.  Up to 8 separate delay taps can be used.</p>
	<p align=center><img src="img/delay.png"><br><small>1 kHz burst, delayed 5.2 ms.</small></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal Input</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Delay Tap #1</td></tr>
		<tr class=odd><td align=center>Out 1</td><td>Delay Tap #2</td></tr>
		<tr class=odd><td align=center>Out 2</td><td>Delay Tap #3</td></tr>
		<tr class=odd><td align=center>Out 3</td><td>Delay Tap #4</td></tr>
		<tr class=odd><td align=center>Out 4</td><td>Delay Tap #5</td></tr>
		<tr class=odd><td align=center>Out 5</td><td>Delay Tap #6</td></tr>
		<tr class=odd><td align=center>Out 6</td><td>Delay Tap #7</td></tr>
		<tr class=odd><td align=center>Out 7</td><td>Delay Tap #8</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>delay</span>(channel, milliseconds);</p>
	<p class=desc>Set output channel (0 to 7) to delay the signals by
		milliseconds.  The maximum delay is approx 333 ms.  The actual delay
		is rounded to the nearest sample.  Each channel can be configured for
		any delay.  There is no requirement to configure the "taps" in increasing
		delay order.
	</p>
	<p class=func><span class=keyword>disable</span>(channel);</p>
	<p class=desc>Disable a channel.  The output of this channel becomes
		silent.  If this channel is the longest delay, memory usage is
		automatically reduced to accomodate only the remaining channels used.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Delay
	</p>
	<h3>Notes</h3>
	<p>Memory for the delayed signal is take from the memory pool allocated by
		<a href="http://www.pjrc.com/teensy/td_libs_AudioConnection.html" target="_blank">AudioMemory()</a>.
		Each block allows about 3 milliseconds of delay, so AudioMemory
		should be increased to allow for the longest delay tap.
	</p>
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<script type="text/x-red" data-template-name="AudioEffectDelay">
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<script type="text/javascript">
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<script type="text/x-red" data-help-name="AudioEffectDelayExternal">
	<h3>Summary</h3>
	<div>
	<p>Delay a signal, using external memory for longer delay times!  Up to 8 separate delay taps can be used.</p>
	<p align=center><img src="img/delay.png"><br><small>1 kHz burst, delayed 5.2 ms.</small></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal Input</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Delay Tap #1</td></tr>
		<tr class=odd><td align=center>Out 1</td><td>Delay Tap #2</td></tr>
		<tr class=odd><td align=center>Out 2</td><td>Delay Tap #3</td></tr>
		<tr class=odd><td align=center>Out 3</td><td>Delay Tap #4</td></tr>
		<tr class=odd><td align=center>Out 4</td><td>Delay Tap #5</td></tr>
		<tr class=odd><td align=center>Out 5</td><td>Delay Tap #6</td></tr>
		<tr class=odd><td align=center>Out 6</td><td>Delay Tap #7</td></tr>
		<tr class=odd><td align=center>Out 7</td><td>Delay Tap #8</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>delay</span>(channel, milliseconds);</p>
	<p class=desc>Set output channel (0 to 7) to delay the signals by
		milliseconds.  The maximum delay is approx 333 ms.  The actual delay
		is rounded to the nearest sample.  Each channel can be configured for
		any delay.  There is no requirement to configure the "taps" in increasing
		delay order.
	</p>
	<p class=func><span class=keyword>disable</span>(channel);</p>
	<p class=desc>Disable a channel.  The output of this channel becomes
		silent.  If this channel is the longest delay, memory usage is
		automatically reduced to accomodate only the remaining channels used.
	</p>
	<h3>Hardware</h3>
	<p>By default, or when <span class=literal>AUDIO_MEMORY_23LC1024</span> is used (see below),
		 a single 23LC1024 RAM chip is used, with these pins:
    <table class=doc align=center cellpadding=3>
        <tr class=top><th>Pin</th><th>Signal</th></tr>
        <tr class=odd><td align=center>6</td><td>CS</td></tr>
        <tr class=odd><td align=center>7</td><td>MOSI</td></tr>
        <tr class=odd><td align=center>12</td><td>MISO</td></tr>
        <tr class=odd><td align=center>14</td><td>SCK</td></tr>
    </table>
	</p>
	<p>When <span class=literal>AUDIO_MEMORY_MEMORYBOARD</span> is used, up to six
		23LC1024 chips are used.
	</p>
	<p align=center><img src="img/memoryboard.jpg"><br><small><a href="https://oshpark.com/shared_projects/KZt5PaU7" target="_blank">Memoryboard 4</a></small></p>
	<p>
    <table class=doc align=center cellpadding=3>
        <tr class=top><th>Pin</th><th>Signal</th></tr>
        <tr class=odd><td align=center>2</td><td>CS0 (encoded)</td></tr>
        <tr class=odd><td align=center>3</td><td>CS1 (encoded)</td></tr>
        <tr class=odd><td align=center>4</td><td>CS2 (encoded)</td></tr>
        <tr class=odd><td align=center>7</td><td>MOSI</td></tr>
        <tr class=odd><td align=center>12</td><td>MISO</td></tr>
        <tr class=odd><td align=center>14</td><td>SCK</td></tr>
    </table>
	</p>
	<p>
	If fewer than 6 chips are soldered, the optional parameter for maximum delay
	must be used.  See below for details.  Each chip provides 1485 ms of delay
	memory, so the total of all objects using AUDIO_MEMORY_MEMORYBOARD must not
	exceed the amount of memory physically present.
	</p>
	<h3>Examples</h3>
	<p>
	<a href="https://www.youtube.com/watch?v=d80d1HWy5_s" target="_blank">Demo Video</a> (YouTube)
	</p>
	<!-- <p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Delay
	</p> -->
	<p>
	<a href="https://forum.pjrc.com/threads/29276-Limits-of-delay-effect-in-audio-library?p=79436&viewfull=1#post79436" target="_blank">Forum Conversaton</a> (with sample code)
	</p>
	<h3>Notes</h3>
	<p>External RAM allows for longer delays without consuming
		limited internal RAM.  However, SPI communication is required,
		which consumes much more CPU time.  The
		<a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html">AudioProcessorUsageMax</a>
		function may be used to monitor how much CPU time is consumed.
	</p>
	<p>You may specify the type of hardware to be used by editing the code.  AUDIO_MEMORY_23LC1024
		specifies a single 23LC1024 chip.  AUDIO_MEMORY_MEMORYBOARD allows using up to 6 of these
		chips.
	</p>
	<p class=desc><span class=keyword>AudioEffectDelayExternal</span>  delayExt1(<span class=literal>AUDIO_MEMORY_23LC1024</span>);
	</p>
	<p>You may also create more than one delay using the same hardware, where the memory is partitioned
		by specifying a maximum delay in milliseconds.  This can be useful if you wish to delay both
		channels of a stereo signal.

	<p class=desc><span class=keyword>AudioEffectDelayExternal</span>  delayExt1(<span class=literal>AUDIO_MEMORY_23LC1024</span>, 700);<br><span class=keyword>AudioEffectDelayExternal</span>  delayExt2(<span class=literal>AUDIO_MEMORY_23LC1024</span>, 700);
	</p>
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        outputs:1,
        category: 'effect-function',
        color:"#E6E0F8",
        icon: "arrow-in.png"
    });
</script>
<script type="text/x-red" data-help-name="AudioEffectBitcrusher">
    <h3>Summary</h3>
    <p>Reduce the samplerate and/or bitdepth of a source signal, resulting in
		a distorted sound.</p>
    <h3>Audio Connections</h3>
    <table class=doc align=center cellpadding=3>
        <tr class=top><th>Port</th><th>Purpose</th></tr>
        <tr class=odd><td align=center>In 0</td><td>Signal Input</td></tr>
        <tr class=odd><td align=center>Out 0</td><td>Signal Output</td></tr>
    </table>
    <h3>Parameters</h3>
    <p class=func><span class=keyword>bits</span>(xcrushBits);</p>
    <p class=desc>xcrushBits sets the bitdepth, from 1 to 16. A Value of 16
    does not crush the bitdepth, and is effectively a passthru for this part
    of the function.</p>

    <p class=func><span class=keyword>sampleRate</span>(xsampleRate);</p>

    <p class=desc>xsampleRate sets the frequency, from 1 to 44100Hz, however it
    works in integer steps so you will only really get a handful of results from
    the many samplerates you can pass. 44100 is passthru.</p>

    <p class=desc>set xbitDepth to 16 and xsampleRate to 44100 to pass audio
    	through without any Bitcrush effect.</p>
    <h3>Examples</h3>
    <p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Bitcrusher
    </p>
    <h3>Notes</h3>
    <p>Needs a lot of improvement. Options for anti-aliasing would be nice in
    the future, but for now, it's rough, it's dirty and it sounds a bit like
    Nine Inch Nails.
    </p>
    <p><a href="http://www.pjrc.com/teensy/td_libs_AudioProcessorUsage.html" target="_blank">AudioNoInterrupts()</a>
        should be used when changing
        settings on multiple objects, so all changes always take effect
        at the same moment.
    </p>
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<script type="text/x-red" data-template-name="AudioEffectBitcrusher">
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<script type="text/javascript">
	RED.nodes.registerType('AudioFilterBiquad',{
	shortName: "biquad",
		inputs:1,
		outputs:1,
		category: 'filter-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioFilterBiquad">
	<h3>Summary</h3>
	<div>
	<p>Biquadratic cascaded filter, useful for all sorts of filtering.
		Up to 4 stages may be cascaded.
	</p>
	<p align=center><img src="img/biquad.png"></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to be filtered</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Filtered Signal Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>setLowpass</span>(stage, frequency, Q);</p>
	<p class=desc>Configure one stage of the filter (0 to 3) with low pass
		response, with the specified corner frequency and Q shape.  If Q is
		higher that 0.7071, be careful of filter gain (see below).
	</p>
	<p class=func><span class=keyword>setHighpass</span>(stage, frequency, Q);</p>
	<p class=desc>Configure one stage of the filter (0 to 3) with high pass
		response, with the specified corner frequency and Q shape.  If Q is
		higher that 0.7071, be careful of filter gain (see below).
	</p>
	<p class=func><span class=keyword>setBandpass</span>(stage, frequency, Q);</p>
	<p class=desc>Configure one stage of the filter (0 to 3) with band pass
		response.  The filter has unity gain at the specified frequency.  Q
		controls the width of frequencies allowed to pass.
	</p>
	<p class=func><span class=keyword>setNotch</span>(stage, frequency, Q);</p>
	<p class=desc>Configure one stage of the filter (0 to 3) with band reject (notch)
		response.  Q controls the width of rejected frequencies.
	</p>
	<p class=func><span class=keyword>setCoefficients</span>(stage, array[5]);</p>
	<p class=desc>Configure one stage of the filter (0 to 3) with an arbitrary
		filter response.  The array of coefficients is in order: B0, B1, B2, A1, A2.
		Each coefficient must be less than 2.0 and greater than -2.0.  The array
		should be type double.  Alternately, it may be type int, where 1.0 is
		represented with 1073741824 (2<sup>30</sup>).
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Filter
	</p>
	<h3>Notes</h3>
	<p>Filters can with gain must have their input signals attenuated, so the
		signal does not exceed 1.0.
	</p>
	<p>This object implements up to 4 cascaded stages.  Unconfigured stages will
		not pass any signal.
	</p>
	<p>Biquad filters with low corner frequency (under about 400 Hz) can run into
		trouble with limited numerical precision, causing the filter to perform
		poorly.  For very low corner frequency, the State Variable (Chamberlin)
		filter should be used.
	</p>
</script>
<script type="text/x-red" data-template-name="AudioFilterBiquad">
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		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
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	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioFilterFIR',{
	shortName: "fir",
		inputs:1,
		outputs:1,
		category: 'filter-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioFilterFIR">
	<h3>Summary</h3>
	<div>
	<p>Finite impulse response filter, useful for all sorts of filtering.
	</p>
	<p align=center><img src="img/fir_filter.png"></p>
	</div>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to be filtered</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Filtered Signal Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>begin</span>(array, length);</p>
	<p class=desc>Initialize the filter.  The array must be 16 bit integers (the
		filter's impulse response), and
		length indicates the number of points in the array.  Array may also be
		FIR_PASSTHRU (length = 0), to directly pass the input to output without
		filtering.
	</p>
	<p class=func><span class=keyword>end</span>();</p>
	<p class=desc>Turn the filter off.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Effects &gt; Filter_FIR
	</p>
	<h3>Notes</h3>
	<p>FIR filters requires more CPU time than Biquad (IIR), but they can
		implement filters with better phase response.
	</p>
	<p>A 100 point filter requires 9% CPU time on Teensy 3.1.  The maximum
		supported filter length is 200 points.
	</p>
	<p>The free
		<a href="http://t-filter.appspot.com/fir/index.html" target="_blank"> TFilter Design Tool</a>
		can be used to create the impulse response array.  Be sure to set the sampling
		frequency to 44117 HZ (it defaults to only 2000 Hz) and the output type to "int" (16 bit).
	</p>
	<p>
		If you use TFilter Design's "C/C++ array" option, it's output has "int" definition, which
		is 32 bits on Teensy 3.1.  Edit "int" to "short" for an array of 16 bit numbers,
		and add "const" to avoid consuming extra RAM.
	</p>
</script>
<script type="text/x-red" data-template-name="AudioFilterFIR">
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	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioFilterStateVariable',{
	shortName: "filter",
		inputs:2,
		outputs:3,
		category: 'filter-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioFilterStateVariable">
	<h3>Summary</h3>
	<p>A State Variable (Chamberlin) Filter with 12 dB/octave roll-off,
		adjustable resonance, and optional signal control of corner
		frequency.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to Filter</td></tr>
		<tr class=odd><td align=center>In 1</td><td>Frequency Control</td></tr>
		<tr class=odd><td align=center>Out 0</td><td>Low Pass Output</td></tr>
		<tr class=odd><td align=center>Out 1</td><td>Band Pass Output</td></tr>
		<tr class=odd><td align=center>Out 2</td><td>High Pass Output</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>frequency</span>(freq);</p>
	<p class=desc>Set the filter's corner frequency.  When a signal is
		connected to the control input, the filter will implement this
		frequency when the signal is zero.
	</p>
	<p class=func><span class=keyword>resonance</span>(Q);</p>
	<p class=desc>Set the filter's resonance.  Q ranges from 0.7 to 5.0.
		Resonance greater than 0.707 will amplify the signal near the
		corner frequency.  You must attenuate the signal before input
		to this filter, to prevent clipping.
	</p>
	<p class=func><span class=keyword>octaveControl</span>(octaves);</p>
	<p class=desc>Set how much (in octaves) the control signal can alter
		the filter's corner freqency.  Range is 0 to 7 octaves.  For
		example, when set to 2.5, a full scale positive signal (1.0) will
		shift the filter frequency up 2.5 octaves, and a full scale negative
		signal will shift it down 2.5 octaves.
	</p>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p>
		When controlled by a signal, the equation for the filter
		frequency is:
	</p>
	<p>
		F = Fcenter * 2^<sup>(signal * octaves)</sup>
		<br><small>If anyone knows how to do HTML equations, please
		help me improve this.....</small>
	</p>
	<p>When operating with signal control of corner frequency, this
		object uses approximately 4% of the CPU time on Teensy 3.1.
	</p>
</script>
<script type="text/x-red" data-template-name="AudioFilterFIR">
	<div class="form-row">
		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
		<input type="text" id="node-input-name" placeholder="Name">
	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioAnalyzePeak',{
	shortName: "peak",
		inputs:1,
		outputs:0,
		category: 'analyze-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioAnalyzePeak">
	<h3>Summary</h3>
	<p>Track the signal peak amplitude.  Very useful for simple
		audio level response projects, and general troubleshooting.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to analyze</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>available</span>();</p>
	<p class=desc>Returns true each time new peak data is available.
	</p>
	<p class=func><span class=keyword>read</span>();</p>
	<p class=desc>Read the highest peak value since the last read.
		Return is from 0.0 to 1.0.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; PeakMeterMono
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; PeakMeterStereo
	</p>
	<h3>Notes</h3>
	<p></p>
</script>
<script type="text/x-red" data-template-name="AudioAnalyzePeak">
	<div class="form-row">
		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
		<input type="text" id="node-input-name" placeholder="Name">
	</div>
</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioAnalyzeFFT256',{
	shortName: "fft256",
		inputs:1,
		outputs:0,
		category: 'analyze-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioAnalyzeFFT256">
	<h3>Summary</h3>
	<p>Compute a 256 point Fast Fourier Transform (FFT) frequency analysis,
		with real value (magnitude) output.  The frequency resolution is
		172 Hz, useful for simple audio visualization.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to convert to frequency bins</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>available</span>();</p>
	<p class=desc>Returns true each time the FFT analysis produces new output data.
	</p>
	<p class=func><span class=keyword>read</span>(binNumber);</p>
	<p class=desc>Read a single frequency bin, from 0 to 127.  The result is scaled
		so 1.0 represents a full scale sine wave.
	</p>
	<p class=func><span class=keyword>read</span>(firstBin, lastBin);</p>
	<p class=desc>Read several frequency bins, returning their sum.  The higher
		audio octaves are represented by many bins, which are typically read
		as a group for audio visualization.
	</p>
	<p class=func><span class=keyword>averageTogether</span>(number);</p>
	<p class=desc>New data is produced very radidly, approximately 344 times
		per second.  Multiple outputs can be averaged together, so available()
		returns true at a slower rate.
	</p>
	<p class=func><span class=keyword>windowFunction</span>(window);</p>
	<p class=desc>Set the window function to be used.  AudioWindowHanning256
		is the default.  Windowing may be disabled by NULL, but windowing
		should be used for all non-periodic (music) signals, and all periodic
		signals that are not exact integer division of the sample rate.
	</p>

	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; MemoryAndCpuUsage
	</p>
	<h3>Notes</h3>
	<p>The raw 16 bit output data bins may be access with myFFT.output[num], where
		num is 0 to 127.</p>
	<p>TODO: caveats about spectral leakage vs frequency precision for arbitrary signals</p>
	<p>Window Types:
		<ul>
		<li><span class=literal>AudioWindowHanning256</span> (default)</li>
		<li><span class=literal>AudioWindowBartlett256</span></li>
		<li><span class=literal>AudioWindowBlackman256</span></li>
		<li><span class=literal>AudioWindowFlattop256</span></li>
		<li><span class=literal>AudioWindowBlackmanHarris256</span></li>
		<li><span class=literal>AudioWindowNuttall256</span></li>
		<li><span class=literal>AudioWindowBlackmanNuttall256</span></li>
		<li><span class=literal>AudioWindowWelch256</span></li>
		<li><span class=literal>AudioWindowHamming256</span></li>
		<li><span class=literal>AudioWindowCosine256</span></li>
		<li><span class=literal>AudioWindowTukey256</span></li>
		</ul>
	</p>
</script>
<script type="text/x-red" data-template-name="AudioAnalyzeFFT256">
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		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
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</script>


<script type="text/javascript">
	RED.nodes.registerType('AudioAnalyzeFFT1024',{
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		outputs:0,
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		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioAnalyzeFFT1024">
	<h3>Summary</h3>
	<p>Compute a 1024 point Fast Fourier Transform (FFT) frequency analysis,
		with real value (magnitude) output.  The frequency resolution is
		43 Hz, useful detailed for audio visualization.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to convert to frequency bins</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>available</span>();</p>
	<p class=desc>Returns true each time the FFT analysis produces new output data.
	</p>
	<p class=func><span class=keyword>read</span>(binNumber);</p>
	<p class=desc>Read a single frequency bin, from 0 to 511.  The result is scaled
		so 1.0 represents a full scale sine wave.
	</p>
	<p class=func><span class=keyword>read</span>(firstBin, lastBin);</p>
	<p class=desc>Read several frequency bins, returning their sum.  The higher
		audio octaves are represented by many bins, which are typically read
		as a group for audio visualization.
	</p>
	<p class=func><span class=keyword>averageTogether</span>(number);</p>
	<p class=desc>This function does nothing.  The 1024 point FFT always
		updates at approximately 86 times per second.
	</p>
	<p class=func><span class=keyword>windowFunction</span>(window);</p>
	<p class=desc>Set the window function to be used.  AudioWindowHanning1024
		is the default.  Windowing may be disabled by NULL, but windowing
		should be used for all non-periodic (music) signals, and all periodic
		signals that are not exact integer division of the sample rate.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; FFT
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; SpectrumAnalyzerBasic
	</p>
	<h3>Notes</h3>
	<p>The raw 16 bit output data bins may be access with myFFT.output[num], where
		num is 0 to 511.</p>
	<p>TODO: caveats about spectral leakage vs frequency precision for arbitrary signals</p>
	<p>Window Types:
		<ul>
		<li><span class=literal>AudioWindowHanning1024</span> (default)</li>
		<li><span class=literal>AudioWindowBartlett1024</span></li>
		<li><span class=literal>AudioWindowBlackman1024</span></li>
		<li><span class=literal>AudioWindowFlattop1024</span></li>
		<li><span class=literal>AudioWindowBlackmanHarris1024</span></li>
		<li><span class=literal>AudioWindowNuttall1024</span></li>
		<li><span class=literal>AudioWindowBlackmanNuttall1024</span></li>
		<li><span class=literal>AudioWindowWelch1024</span></li>
		<li><span class=literal>AudioWindowHamming1024</span></li>
		<li><span class=literal>AudioWindowCosine1024</span></li>
		<li><span class=literal>AudioWindowTukey1024</span></li>
		</ul>
	</p>
	<p>1024 point FFT has a peak CPU usage of approx 52% on Teensy 3.1.
		Average usage is much lower.  Future versions might distribute the
		load more evenly over time....
	</p>
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<script type="text/x-red" data-template-name="AudioAnalyzeFFT1024">
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<script type="text/javascript">
	RED.nodes.registerType('AudioAnalyzeToneDetect',{
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		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioAnalyzeToneDetect">
	<h3>Summary</h3>
	<p>Detect the level of a single tone</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to analyze</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>frequency</span>(freq);</p>
	<p class=desc>Set the frequency to detect.  The default detection time
		will be 10 cycles of this frequency.
	</p>
	<p class=func><span class=keyword>frequency</span>(freq, cycles);</p>
	<p class=desc>Set the frequency to detect, and the number of cycles.
		Longer detection time (more cycles) will give higher precision,
		but of course slower response.
	</p>
	<p class=func><span class=keyword>available</span>();</p>
	<p class=desc>Returns true (non-zero) each time a detection interval
		(number of cycles) completed and a new level is detected.
	</p>
	<p class=func><span class=keyword>read</span>();</p>
	<p class=desc>Read the detected signal level.  Range is 0 to 1.0.
	</p>
	<p class=func><span class=keyword>threshold</span>(level);</p>
	<p class=desc>Set a detection threshold, where the bool test operation
		will return true if at or above this level, or false when below.
	</p>
	<p class=func>(bool)</p>
	<p class=desc>By testing the object as a boolean value, you can respond
		to detection of a tone.
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; DialTone_Serial
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; Analysis &gt; DialTone_7segment
	</p>
	<h3>Notes</h3>
	<p>Low frequency detection has trouble with numerical precision.
		Works really well for all 8 DTMF frequencies, but fails for
		detecting "sub audible tones" used in some control applications.</p>
	<p>The (bool) test continues to return true until the next detection
		interval (the configured number of cycles).  This behavior may
		change in future versions, for a single true each time the signal
		is detected, and then false for the remainder of that interval.</p>
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<script type="text/x-red" data-template-name="AudioAnalyzeToneDetect">
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<script type="text/javascript">
	RED.nodes.registerType('AudioAnalyzePrint',{
	shortName: "print",
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		outputs:0,
		category: 'analyze-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioAnalyzePrint">
	<h3>Summary</h3>
	<p>Print raw audio data to the Arduino Serial Monitor.  This
		object creates massive output quickly, and should not normally be used.</p>
	<h3>Audio Connections</h3>
	<table class=doc align=center cellpadding=3>
		<tr class=top><th>Port</th><th>Purpose</th></tr>
		<tr class=odd><td align=center>In 0</td><td>Signal to print</td></tr>
	</table>
	<h3>Functions</h3>
	<p class=func><span class=keyword>name</span>(string);</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>trigger</span>();</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>trigger</span>(level, edge);</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>delay</span>(samples);</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>length</span>(samples);</p>
	<p class=desc>blah blah blah blah
	</p>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; 
	</p>-->
	<h3>Notes</h3>
	<p>This object doesn't work very well and probably should not be used.</p>
</script>
<script type="text/x-red" data-template-name="AudioAnalyzePrint">
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		<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
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<script type="text/javascript">
	RED.nodes.registerType('AudioControlSGTL5000',{
	shortName: "sgtl5000",
		inputs:0,
		outputs:0,
		category: 'control-function',
		color:"#E6E0F8",
		icon: "arrow-in.png"
	});
</script>
<script type="text/x-red" data-help-name="AudioControlSGTL5000">
	<h3>Summary</h3>
	<p>Control the SGTL5000 chip on the
		<a href="http://www.pjrc.com/store/teensy3_audio.html" target="_blank">audio shield</a>.
		SGTL5000 is always used in slave mode, where Teensy controls
		all I2S timing.
	</p>
	<p align=center><img src="img/sgtl5000closeup.jpg"></p>
	<h3>Audio Connections</h3>
	<p>This object has no audio inputs or outputs.  Separate i2s objects
		are used to send and receive audio data.  I2S master mode objects
		must be used, because this object configures the SGTL5000 in slave
		mode, where it depends on Teensy to provide all I2S clocks.
		This object controls
		how the SGTL5000 will use those I2S audio streams.</p>

	<h3>Functions</h3>
	<p>These are the most commonly used SGTL5000 functions.</p>
	<p class=func><span class=keyword>enable</span>();</p>
	<p class=desc>Start the SGTL5000.  This function should be called first.
	</p>
	<p class=func><span class=keyword>volume</span>(level);</p>
	<p class=desc>Set the headphone volume level.  Range is 0 to 1.0, but
		0.8 corresponds to the maximum undistorted output for a full scale
		signal.  Usually 0.5 is a comfortable listening level.  The line
		level outputs are <em>not</em> changed by this function.
	</p>
	<p class=func><span class=keyword>inputSelect</span>(input);</p>
	<p class=desc>Select which input to use: AUDIO_INPUT_LINEIN or AUDIO_INPUT_MIC.
	</p>
	<p class=func><span class=keyword>micGain</span>(dB);</p>
	<p class=desc>When using the microphone input, set the amplifier gain.
		The input number is in decibels, from 0 to 63.
	</p>

	<h3>Signal Levels</h3>

	<p>The default signal levels should be used for most applications,
		but these functions allow you to customize the analog signals.</p>

	<p class=func><span class=keyword>muteHeadphone</span>();</p>
	<p class=desc>Silence the headphone output.
	</p>
	<p class=func><span class=keyword>unmuteHeadphone</span>();</p>
	<p class=desc>Turn the headphone output on.
	</p>
	<p class=func><span class=keyword>muteLineout</span>();</p>
	<p class=desc>Silence the line level outputs.
	</p>
	<p class=func><span class=keyword>unmuteLineout</span>();</p>
	<p class=desc>Turn the line level outputs on.
	</p>
	<p class=func><span class=keyword>lineInLevel</span>(both);</p>
	<p class=desc style="padding-bottom:0.2em;">Adjust the sensitivity of the line-level inputs.
		Fifteen settings are possible:
	</p>
<pre class="desc">
 0: 3.12 Volts p-p
 1: 2.63 Volts p-p
 2: 2.22 Volts p-p
 3: 1.87 Volts p-p
 4: 1.58 Volts p-p
 5: 1.33 Volts p-p  (default)
 6: 1.11 Volts p-p
 7: 0.94 Volts p-p
 8: 0.79 Volts p-p
 9: 0.67 Volts p-p
10: 0.56 Volts p-p
11: 0.48 Volts p-p
12: 0.40 Volts p-p
13: 0.34 Volts p-p
14: 0.29 Volts p-p
15: 0.24 Volts p-p
</pre>
	<p class=func><span class=keyword>lineInLevel</span>(left, right);</p>
	<p class=desc>Adjust the sensitivity of the line-level inputs, with different
		settings for left and right.  The same 15 settings are available.
	</p>
	<p class=func><span class=keyword>lineOutLevel</span>(both);</p>
	<p class=desc style="padding-bottom:0.2em;">Adjust the line level output
		voltage range.  The following settings are possible:
	</p>
<pre class="desc">
13: 3.16 Volts p-p
14: 2.98 Volts p-p
15: 2.83 Volts p-p
16: 2.67 Volts p-p
17: 2.53 Volts p-p
18: 2.39 Volts p-p
19: 2.26 Volts p-p
20: 2.14 Volts p-p
21: 2.02 Volts p-p
22: 1.91 Volts p-p
23: 1.80 Volts p-p
24: 1.71 Volts p-p
25: 1.62 Volts p-p
26: 1.53 Volts p-p
27: 1.44 Volts p-p
28: 1.37 Volts p-p
29: 1.29 Volts p-p  (default)
30: 1.22 Volts p-p
31: 1.16 Volts p-p
</pre>
	<p class=func><span class=keyword>lineOutLevel</span>(left, right);</p>
	<p class=desc>Adjust the line level outout voltage range, with separate
		settings for left and right.  The same settings (13 to 31) are available.
	</p>


	<h3>Signal Conditioning</h3>

	<p>Usually these digital signal conditioning features should be left at their
		default settings.
	</p>

	<p class=func><span class=keyword>adcHighPassFilterFreeze</span>();</p>
	<p class=desc>By default, the analog input (either line-level inputs or mic)
		is high-pass filtered, to remove any DC component.  This function
		freezes the filter, so the current DC component is still substracted, but
		the filter stops tracking any DC or low frequency changes.
	</p>
	<p class=func><span class=keyword>adcHighPassFilterDisable</span>();</p>
	<p class=desc>Completely disable the analog input filter.  DC and sub-audible
		low frequencies are allowed to enter the digital signal.
	</p>
	<p class=func><span class=keyword>adcHighPassFilterEnable</span>();</p>
	<p class=desc>Turn the DC-blocking filter back on, if disabled, or
		allows it to resume tracking DC and low frequency changes, if
		previously frozen. This is the default setting.
	</p>
	<p class=func><span class=keyword>dacVolume</span>(both);</p>
	<p class=desc>Normally output volume should be used with volume(), which
		changes the analog gain in the headphone amplifier.  This function
		on the other hand controls digital attenuation before conversion to analog, which
		reduces resolution, but allows another fine control of output
		signal level.  The ranges is 0 to 1.0, with the default (no digital attenuation)
		at 1.0.
	</p>
	<p  class=desc>dacVolume uses zero-crossing detect to avoid clicks, and ramping is handled by
	the chip so that a new volume may be set directly in a single call.
	</p>
	<p class=func><span class=keyword>dacVolume</span>(left, right);</p>
	<p class=desc>Adjust the digital output volume separately on left and
		right channels.
	</p>


	<h3>Audio Processor</h3>

	<p>The optional digital audio processor is capable of implementing
		one or more of: automatic volume control, surround sound control,
		bass enhancement, and tonal adjustments (either a
		simple tone control, or a parametric equalizer, or a graphic equalizer),
		in that order.
	</p>
	<p>These signal processing features are implemented in the SGTL5000 chip,
		so they do not consume CPU time on Teensy. However, the order of
		these processes is fixed in the hardware.
	</p>
	<p>It is good practice to mute the outputs before enabling or disabling
	the Audio Processor, to avoid clicks or thumps.
	</p>

	<p class=func><span class=keyword>audioPreProcessorEnable</span>();</p>
	<p class=desc>Enable the audio processor to pre-process the input
		(from either line-level inputs or microphone) before it's sent
		to Teensy by I2S.
	</p>
	<p class=func><span class=keyword>audioPostProcessorEnable</span>();</p>
	<p class=desc>Enable the audio processor to post-process Teensy's
		I2S output before it's turned into analog signals for the
		headphones and/or line level outputs.
	</p>
	<p class=func><span class=keyword>audioProcessorDisable</span>();</p>
	<p class=desc>Disable the audio processor.
	</p>
	<p class=func><span class=keyword>autoVolumeControl</span>(maxGain, response, hardLimit, threshold, attack, decay);</p>
	<p class=desc>Configures the auto volume control, which is implemented as a compressor/expander
	or hard limiter. 	<em>maxGain</em> is the maximum gain that can be applied for expanding, and
	can take one of three values: 0 (0dB), 1 (6.0dB) and 2 (12dB). Values greater than 2 are treated
	as 2. <em>response</em> controls the integration time for the compressor and can take
	four values: 0 (0ms), 1 (25ms), 2 (50ms) or 3 (100ms). Larger values average the volume
	over a longer time, allowing short-term peaks through.
	</p>
	<p class=desc>If <em>hardLimit</em> is 0, a 'soft
	knee' compressor is used to progressively compress louder values which are near to or above the
	threashold (the louder they are, the greater the compression). If it is 1, a hard compressor
	is used (all values above the threashold are the same loudness). The <em>threashold</em> is specified
	as a float in the range 0dBFS to -96dBFS, where -18dBFS is a typical value.
	<em>attack</em> is a float controlling the rate of decrease in gain when the signal is over
	threashold, in dB/s. <em>decay</em> controls how fast gain is restored once the level
	drops below threashold, again in dB/s. It is typically set to a longer value than attack.
	</p>
	<p class=func><span class=keyword>autoVolumeEnable</span>();</p>
	<p class=desc>Enables auto volume control, using the previously specified settings.
	</p>
	<p class=func><span class=keyword>autoVolumeDisable</span>();</p>
	<p class=desc>Disables auto volume control.
	</p>

	<p class=func><span class=keyword>surroundSoundEnable</span>();</p>
	<p class=desc>Enable virtual surround processing, to give a broader and
	deeper stereo image (even with mono input).
	</p>
	<p class=func><span class=keyword>surroundSoundDisable</span>();</p>
	<p class=desc>Disable virtual surround processing. Before disabling, ramp up
	the width to maximum to avoid pops.
	</p>
	<p class=func><span class=keyword>surroundSound</span>(width);</p>
	<p class=desc>Configures virtual surround width from 0 (mono) to 7 (widest).
	</p>
	<p class=func><span class=keyword>surroundSound</span>(width, select);</p>
	<p class=desc>Configures virtual surround width from 0 (mono) to 7 (widest).
	<em>select</em> may be set to 1 (disable), 2 (mono input) or 3 (stereo input).
	</p>

	<p class=func><span class=keyword>enhanceBassEnable</span>();</p>
	<p class=desc>Enable bass enhancement. A mono, low-pass filtered copy of
	the original stereo signal has bass levels boosted and is then mixed back into
	the stereo signal, which is then optionally high pass filtered (to remove
	inaudible subsonic frequencies).
	</p>
	<p class=func><span class=keyword>enhanceBassDisable</span>();</p>
	<p class=desc>Disable bass enhancement. Before disabling, ramp down the bass
	enhancement level to zero.
	</p>
	<p class=func><span class=keyword>enhanceBass</span>(lr_lev, bass_lev);</p>
	<p class=desc>Configures the bass enhancement by setting the levels of the
	original stereo signal and the bass-enhanced mono level which will be mixed together.
	There is no high-pass filter.
	</p>
	<p  class=desc>When changing bass level, call this function repeatedly to ramp up or down the bass in
	steps of 0.5dB, to avoid pops.
	</p>
	<p class=func><span class=keyword>enhanceBass</span>(lr_lev, bass_lev, hpf_bypass, cutoff);</p>
	<p class=desc>Configures the bass enhancement by setting the levels of the
	original stereo signal and the bass-enhanced mono level which will be mixed together.
	The high-pass filter may be enabled (0) or bypassed (1). The cutoff frequency is specified
	as follows:
	</p>
	<pre class="desc">
value  frequency
 0      80Hz
 1     100Hz
 2     125Hz
 3     150Hz
 4     175Hz
 5     200Hz
 6     225Hz
</pre>
	<p  class=desc>When changing bass level, call this function repeatedly to ramp up or down the bass in
	steps of 0.5dB, to avoid pops.
	</p>

	<p class=func><span class=keyword>eqSelect</span>(n);</p>
	<p class=desc>Selects the type of frequency control, where <em>n</em> is
	one of</p>
	<p class=desc><b>FLAT_FREQUENCY (0)</b><br>
    Equalizers and tone controls disabled, flat frequency response.</p>
    <p class=desc><b>PARAMETRIC_EQUALIZER (1)</b><br>
    Enables the 7-band parametric equalizer, thus disabling the
	tone controls and graphic equalizer.</p>
    <p class=desc><b>TONE_CONTROLS (2)</b><br>
    Enables bass and treble tone controls, disabling the parametric
	equalization and graphic equalizer.</p>
    <p class=desc><b>GRAPHIC_EQUALIZER (3)</b><br>
    Enables the five-band graphic equalizer, disabling the parametric
	equalization and tone controls.</p>


	<p class=func><span class=keyword>eqBands</span>(bass, treble);</p>
	<p class=desc>Configures bass and treble tone controls, which are
	implemented as one second order low pass filter (bass) in parallel with
	one second order high pass filter (treble).
	</p>
	<p class=desc>When changing bass or treble level, call this function repeatedly to ramp
	up or down the level in steps of 0.04 (=0.5dB) or so, to avoid pops.
	</p>
	<p class=func><span class=keyword>eqBands</span>(bass, mid_bass, midrange, mid_treble, treble);</p>
	<p class=desc>Configures the graphic equalizer. It is implemented by five parallel,
	second order biquad filters with fixed frequencies of 115Hz, 330Hz, 990Hz, 3kHz,
	and 9.9kHz. Each band has a range of adjustment from 1.00 (+12dB) to -1.00 (-11.75dB).
	</p>
	<p class=func><span class=keyword>eqBand</span>(bandNum, n);</p>
	<p class=desc>Configures the gain or cut on one band in the graphic equalizer.
	<em>bandnum</em> can range from 1 to 5; <em>n</em> is a float in the range 1.00 to -1.00.
	</p>
	<p  class=desc>When changing a band, call this function repeatedly to ramp up the gain in steps of 0.5dB,
	to avoid pops.
	</p>

	<p class=func><span class=keyword>eqFilter</span>(filterNum, filterParameters);</p>
	<p class=desc>Configurs the parametric equalizer. The number of filters (1 to 7)
	is specified along with  a pointer to an array of filter coefficients.
	The parametric equalizer is implemented using 7 cascaded, second order bi-quad
	filters whose frequencies, gain, and Q may be freely configured, but each filter
	can only be specified as a set of filter coefficients.
	</p>
	<p class=func><span class=keyword>eqFilterCount</span>(n);</p>
	<p class=desc>Enables zero or more of the already enabled parametric filters.
	</p>

	<h3>Examples</h3>
	<p>Nearly all of the library's examples use this object.  These
		examples demonstrate its special features.
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; PassThroughStereo
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; SGTL5000 &gt; dap_bass_enhance
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; SGTL5000 &gt; dap_avc_agc
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; SGTL5000 &gt; balanceDAC
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; SGTL5000 &gt; balanceHP
	</p>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; SGTL5000 &gt; CalcBiquadToneControlDAP
	</p>
	<h3>Notes</h3>
	<p>TODO: add example with rock/classical/speech presets, where rock uses bass boost
	and surround enhancement while speech uses bandpass filtering and auto volume control
	compression.
	</p>
	<p>TODO: add example with two analogRead pots for bass and treble to demonstrate ramping.
	</p>
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<script type="text/x-red" data-help-name="AudioControlWM8731">
	<h3>Summary</h3>
	<p>Control a WM8731 chip in slave mode, where it receives all clocks from Teensy</p>
	<h3>Audio Connections</h3>
	<p>This object has no audio inputs or outputs.  Separate i2s objects
		are used to send and receive audio data.  I2S master mode objects
		must be used, since this control object configures the WM8731 into
		slave mode.
	</p>
	<h3>Functions</h3>
	<p class=func><span class=keyword>enable</span>();</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>disable</span>();</p>
	<p class=desc>not implemented
	</p>
	<p class=func><span class=keyword>volume</span>(level);</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>inputLevel</span>(level);</p>
	<p class=desc>not implemented
	</p>
	<p class=func><span class=keyword>inputSelect</span>(input);</p>
	<p class=desc>not implemented
	</p>
	<!--<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt;
	</p>-->
	<h3>Notes</h3>
	<p></p>
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<script type="text/x-red" data-help-name="AudioControlWM8731master">
	<h3>Summary</h3>
	<p>Control a WM8731 chip in master mode, where it controls all I2S timing.</p>
	<h3>Audio Connections</h3>
	<p>This object has no audio inputs or outputs.  Separate i2s objects
		are used to send and receive audio data.  I2S slave mode objects
		must be used, since this control object configures the WM8731 into
		master mode.
	</p>
	<h3>Functions</h3>
	<p class=func><span class=keyword>enable</span>();</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>disable</span>();</p>
	<p class=desc>not implemented
	</p>
	<p class=func><span class=keyword>volume</span>(level);</p>
	<p class=desc>blah blah blah blah
	</p>
	<p class=func><span class=keyword>inputLevel</span>(level);</p>
	<p class=desc>not implemented
	</p>
	<p class=func><span class=keyword>inputSelect</span>(input);</p>
	<p class=desc>not implemented
	</p>
	<h3>Examples</h3>
	<p class=exam>File &gt; Examples &gt; Audio &gt; HardwareTesting &gt; WM8731MikroSine
	</p>
	<h3>Notes</h3>
	<p></p>
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