visus
/
teensy-audio


			
				
					
						
						
							
							
	<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>