OpenAudio_ArduinoLibrary/examples/BasicGain_Float/BasicGain_Float.ino

/*
   BasicGain

   Created: Chip Audette, Nov 2016
   Purpose: Process audio by applying gain.
            Demonstrates audio processing using floating point data type.

   Uses Teensy Audio Adapter.
   Assumes microphones (or whatever) are attached to the LINE IN (stereo)
   Use potentiometer mounted to Audio Board to control the amount of gain.

   MIT License.  use at your own risk.
*/

//These are the includes from the Teensy Audio Library
#include <Audio.h>      //Teensy Audio Library
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>

#include <OpenAudio_ArduinoLibrary.h> //for AudioConvert_I16toF32, AudioConvert_F32toI16, and AudioEffectGain_F32

//create audio library objects for handling the audio
AudioControlSGTL5000    sgtl5000_1;    //controller for the Teensy Audio Board
AudioInputI2S           i2s_in;        //Digital audio *from* the Teensy Audio Board ADC.  Sends Int16.  Stereo.
AudioOutputI2S          i2s_out;       //Digital audio *to* the Teensy Audio Board DAC.  Expects Int16.  Stereo
AudioConvert_I16toF32   int2Float1, int2Float2;    //Converts Int16 to Float.  See class in AudioStream_F32.h
AudioEffectGain_F32     gain1, gain2;  //Applies digital gain to audio data.  Expected Float data.  
AudioConvert_F32toI16   float2Int1, float2Int2;    //Converts Float to Int16.  See class in AudioStream_F32.h

//Make all of the audio connections
AudioConnection         patchCord1(i2s_in, 0, int2Float1, 0);    //connect the Left input to the Left Int->Float converter
AudioConnection         patchCord2(i2s_in, 1, int2Float2, 0);    //connect the Right input to the Right Int->Float converter
AudioConnection_F32     patchCord10(int2Float1, 0, gain1, 0);    //Left.  makes Float connections between objects
AudioConnection_F32     patchCord11(int2Float2, 0, gain2, 0);    //Right.  makes Float connections between objects
AudioConnection_F32     patchCord12(gain1, 0, float2Int1, 0);    //Left.  makes Float connections between objects
AudioConnection_F32     patchCord13(gain2, 0, float2Int2, 0);    //Right.  makes Float connections between objects
AudioConnection         patchCord20(float2Int1, 0, i2s_out, 0);  //connect the Left float processor to the Left output
AudioConnection         patchCord21(float2Int2, 0, i2s_out, 1);  //connect the Right float processor to the Right output

// which input on the audio shield will be used?
const int myInput = AUDIO_INPUT_LINEIN;
//const int myInput = AUDIO_INPUT_MIC;

//I have a potentiometer on the Teensy Audio Board
#define POT_PIN A1  //potentiometer is tied to this pin

// define the setup() function, the function that is called once when the device is booting
void setup() {
  Serial.begin(115200);   //open the USB serial link to enable debugging messages
  delay(500);             //give the computer's USB serial system a moment to catch up.
  Serial.println("OpenAudio_ArduinoLibrary BasicGain_Float..."); 
  
  // Audio connections require memory
  AudioMemory(10);      //allocate Int16 audio data blocks
  AudioMemory_F32(10);  //allocate Float32 audio data blocks

  // Enable the audio shield, select input, and enable output
  sgtl5000_1.enable();                   //start the audio board
  sgtl5000_1.inputSelect(myInput);       //choose line-in or mic-in
  sgtl5000_1.volume(0.8);                //volume can be 0.0 to 1.0.  0.5 seems to be the usual default.
  sgtl5000_1.lineInLevel(10,10);         //level can be 0 to 15.  5 is the Teensy Audio Library's default
  sgtl5000_1.adcHighPassFilterDisable(); //reduces noise.  https://forum.pjrc.com/threads/27215-24-bit-audio-boards?p=78831&viewfull=1#post78831

  // setup any other other features
  pinMode(POT_PIN, INPUT); //set the potentiometer's input pin as an INPUT

} //end setup()


// define the loop() function, the function that is repeated over and over for the life of the device
unsigned long updatePeriod_millis = 100; //how many milliseconds between updating gain reading?
unsigned long lastUpdate_millis = 0;
unsigned long curTime_millis = 0;
int prev_gain_dB = 0;
void loop() {
  //choose to sleep ("wait for interrupt") instead of spinning our wheels doing nothing but consuming power
  asm(" WFI");  //ARM-specific.  Will wake on next interrupt.  The audio library issues tons of interrupts, so we wake up often.
  
  //has enough time passed to try updating the GUI?
  curTime_millis = millis(); //what time is it right now
  if (curTime_millis < lastUpdate_millis) lastUpdate_millis = 0; //handle wrap-around of the clock
  if ((curTime_millis - lastUpdate_millis) > updatePeriod_millis) { //is it time to update the user interface?
    
    //read potentiometer
    float val = float(analogRead(POT_PIN)) / 1024.0; //0.0 to 1.0
    val = 0.1*(float)((int)(10.0*val + 0.5));  //quantize so that it doesn't chatter
        
    //compute desired digital gain
    const float min_gain_dB = -20.0, max_gain_dB = 40.0; //set desired gain range
    float gain_dB = min_gain_dB + (max_gain_dB - min_gain_dB)*val; //computed desired gain value in dB

    //if the gain is different than before, set the new gain value
    if (abs(gain_dB - prev_gain_dB) > 1.0) { //is it different than before
      gain1.setGain_dB(gain_dB);  //set the gain of the Left-channel gain processor
      gain2.setGain_dB(gain_dB);  //set the gain of the Right-channel gain processor
      Serial.print("Digital Gain dB = "); Serial.println(gain_dB); //print text to Serial port for debugging
      prev_gain_dB = gain_dB;  //we will use this value the next time around
    }
 
    lastUpdate_millis = curTime_millis; //we will use this value the next time around.
  } // end if

} //end loop();