Add AVC control to control_sgtl5000.* and example

Added
AudioControlSGTL5000::dap_avc(..);
AudioControlSGTL5000::dap_avc_enable(..);

SGTL5000_Specific/dap_avc_agc example sketch

Also added 'public domain...' line to all my examples.

control_sgtl5000.cpp

 	unsigned short m=(0xFC-calcVol(right,0xC0))<<8|(0xFC-calcVol(left,0xC0));
 	return modify(CHIP_DAC_VOL,m,65535);
 }
+
 // DAP_CONTROL
 unsigned short AudioControlSGTL5000::dap_mix_enable(uint8_t n)
 {
 	modify(DAP_FILTER_COEF_ACCESS,(uint16_t)filterNum,15); 
 }
 
+/* Valid values for dap_avc parameters
+
+	maxGain; Maximum gain that can be applied
+	0 - 0 dB
+	1 - 6.0 dB
+	2 - 12 dB
+	
+	lbiResponse; Integrator Response
+	0 - 0 mS
+	1 - 25 mS
+	2 - 50 mS
+	3 - 100 mS
+	
+	hardLimit
+	0 - Hard limit disabled. AVC Compressor/Expander enabled.
+	1 - Hard limit enabled. The signal is limited to the programmed threshold (signal saturates at the threshold)
+	
+	threshold
+	floating point in range 0 to -96 dB
+	
+	attack
+	floating point figure is dB/s rate at which gain is increased
+	
+	decay
+	floating point figure is dB/s rate at which gain is reduced
+*/
+unsigned short AudioControlSGTL5000::dap_avc(uint8_t maxGain, uint8_t lbiResponse, uint8_t hardLimit, float threshold, float attack, float decay)
+{
+	if(maxGain>2) maxGain=2;
+	lbiResponse&=3;
+	hardLimit&=1;
+	uint8_t thresh=(pow(10,threshold/20)*0.636)*pow(2,15);
+	uint8_t att=(1-pow(10,-(attack/(20*44100))))*pow(2,19);
+	uint8_t dec=(1-pow(10,-(decay/(20*44100))))*pow(2,23);
+	write(DAP_AVC_THRESHOLD,thresh);
+	write(DAP_AVC_ATTACK,att);
+	write(DAP_AVC_DECAY,dec);
+	return 	modify(DAP_AVC_CTRL,maxGain<<12|lbiResponse<<8|hardLimit<<5,3<<12|3<<8|1<<5);
+}
+unsigned short AudioControlSGTL5000::dap_avc_enable(uint8_t n)
+{
+	n&=1;
+	return modify(DAP_AVC_CTRL,n,1);
+}
+unsigned short AudioControlSGTL5000::dap_avc_enable(void)
+{
+	return modify(DAP_AVC_CTRL,1,1);
+}
+
 unsigned char AudioControlSGTL5000::calcVol(float n, unsigned char range)
 {
 	n=(n*(((float)range)/100))+0.499;
 	return (unsigned char)n;
 }
 
+
 // if(SGTL5000_PEQ) quantization_unit=524288; if(AudioFilterBiquad) quantization_unit=2147483648;
 void calcBiquad(uint8_t filtertype, float fC, float dB_Gain, float Q, uint32_t quantization_unit, uint32_t fS, int *coef)
 {

control_sgtl5000.h

 	void dap_audio_eq_geq(float bass, float mid_bass, float midrange, float mid_treble, float treble);
 	void dap_audio_eq_tone(float bass, float treble);
 	void load_peq(uint8_t filterNum, int *filterParameters);
-	
-	
-protected:
+	unsigned short dap_avc(uint8_t maxGain, uint8_t lbiResponse, uint8_t hardLimit, float threshold, float attack, float decay);
+	unsigned short dap_avc_enable(uint8_t n);
+	unsigned short dap_avc_enable(void);
+
+	protected:
 	bool muted;
 	bool volumeInteger(unsigned int n); // range: 0x00 to 0x80
 	uint16_t ana_ctrl;

examples/CalcBiquadToneControl/CalcBiquadToneControl.ino

-// Tone example using AudioFilterBiquad object and calcBiquad filter calculator routine.
+/* Tone example using AudioFilterBiquad object and calcBiquad filter calculator routine.
+
+This example code is in the public domain
+*/
 
 #include <Audio.h>
 #include <Wire.h>

examples/SGTL5000_Specific/CalcBiquadToneControlDAP/CalcBiquadToneControlDAP.ino

-// Tone example using SGTL5000 DAP PEQ filters and calcBiquad filter calculator routine.
+/* Tone example using SGTL5000 DAP PEQ filters and calcBiquad filter calculator routine.
 
+This example code is in the public domain
+*/
 #include <Audio.h>
 #include <Wire.h>
 #include <SD.h>

examples/SGTL5000_Specific/balanceDAC/balanceDAC.ino

-// DAC balance example: Will influence both HP & LO outputs.
+/* DAC balance example: Will influence both HP & LO outputs.
+
+This example code is in the public domain
+*/
 
 #include <Audio.h>
 #include <Wire.h>

examples/SGTL5000_Specific/balanceHP/balanceHP.ino

-// HP balance example: Will influence only HP output.
+/* HP balance example: Will influence only HP output.
+
+This example code is in the public domain
+*/
 
 #include <Audio.h>
 #include <Wire.h>

examples/SGTL5000_Specific/dap_avc_agc/dap_avc_agc.ino

+/* DAP AVC example; AVC is SGTL5000 equiv of AGC
+
+This example code is in the public domain
+*/
+
+#include <Audio.h>
+#include <Wire.h>
+#include <SD.h>
+
+
+const int myInput = AUDIO_INPUT_LINEIN;
+// const int myInput = AUDIO_INPUT_MIC;
+
+// Create the Audio components.  These should be created in the
+// order data flows, inputs/sources -> processing -> outputs
+//
+
+AudioInputI2S       audioInput;         // audio shield: mic or line-in
+AudioOutputI2S      audioOutput;        // audio shield: headphones & line-out
+
+// Create Audio connections between the components
+//
+AudioConnection c1(audioInput, 0, audioOutput, 0); // left passing through
+AudioConnection c2(audioInput, 1, audioOutput, 1); // right passing through
+
+// Create an object to control the audio shield.
+// 
+AudioControlSGTL5000 audioShield;
+
+void setup() {
+  // Audio connections require memory to work.  For more
+  // detailed information, see the MemoryAndCpuUsage example
+  AudioMemory(4);
+  // Enable the audio shield and set the output volume.
+  audioShield.enable();
+  audioShield.inputSelect(myInput);
+  audioShield.volume(75);
+  audioShield.unmuteLineout();
+  // have to enable DAP to use AVC
+  audioShield.dap_enable();
+  // here are some settings for AVC that have a fairly obvious effect
+  audioShield.dap_avc(2,1,0,-5,0.5,0.5); // see comments starting line #699 of control_sgtl5000.cpp in ./libraries/audio/
+  // AVC has its own enable/disable bit
+  audioShield.dap_avc_enable(); // you can use audioShield.dap_avc_enable(0); to turn off AVC
+}
+
+elapsedMillis chgMsec=0;
+float lastVol=1024;
+
+void loop() {
+  // every 10 ms, check for adjustment the balance & vol
+  if (chgMsec > 10) { // more regular updates for actual changes seems better.
+    float vol1=analogRead(15)/10.23;
+    vol1=(int)vol1;
+    if(lastVol!=vol1)
+    {
+      audioShield.volume(vol1);
+      lastVol=vol1;
+    }
+    chgMsec = 0;
+  }
+}
+