chipKIT DP32 Simple dub Siren Code

Sampling Rate 22.050 kHz, with 12 bit DAC MCP4725 ( breakout board)

Using button 2(Pin 17) on DP32 and Variable pot (A2).

For the signal out, the ac coupling circuit from previous post is necessary.

*Check also I2C Speed post HERE

#include <sys/attribs.h>
#include <Wire.h>
#define MCP4725_DID 96 // define device id - see datasheet
//
#define SYS_FREQ            (40000000L)
#define PB_DIV              4
#define PRESCALE            2
#define FRQ                 22050 //21504
#define T1_TICK             (SYS_FREQ/PB_DIV/PRESCALE/FRQ)

#define WAVE_SAMPLES 256
const int buttonPin = 17; 
// variables will change:
int buttonState = 0;         // variable to read the pushbutton status
uint8_t playOn=0;            // Variable of play state/button state
volatile uint16_t a;
uint16_t b;
uint16_t d;
uint16_t e=0;
uint16_t inc;
uint8_t statedown=0;
boolean c;
boolean togg;
uint16_t sineData [WAVE_SAMPLES];
//


void setup()
{
  // Serial.begin(57600);
  initTmr();
  pinMode(A2, INPUT); //
  pinMode(13, OUTPUT); //
  //set pins to output because they are addressed in the main loop
  sine ();  
  Wire.begin() ;
}

void loop()
{
  uint16_t aIn =analogRead(A2);
  inc=aIn >>4;
  buttonState = digitalRead(buttonPin);

  // check if the pushbutton is pressed.
  // if it is, the buttonState is HIGH:
  if (buttonState == HIGH) {  
    playOn=1;   
    // play is On    
  } 
  else{
    playOn=0;
    // play is Off

  }
  if(c !=togg){

    if(playOn==1){

      a = a++  ;
      a+= (inc+(e >>4));
      if(a>=WAVE_SAMPLES){
        a-=WAVE_SAMPLES;
        // ramp up or down variables
        if (statedown==0){
          e++;
          if(e>=1023){
            statedown=1;
            e--;
          }
        }
        else{
          e--;
          if (e==0){
            statedown=0;
            e++;
          }
        }
      }
      //
      Wire.beginTransmission(MCP4725_DID); //device adress
      Wire.send(64);                     // cmd to update the DAC
      Wire.send(sineData[a] >> 4);        // the 8 most significant bits...
      Wire.send((sineData[a] & 15) << 4); /* the 4 least significant bis...*/
      Wire.endTransmission();
      /*
       */
    } 
  }//
  c=togg;
}

// call interrupt handling vector
extern "C" {

  void __ISR(16, ipl6) int1Handler(void) 
  {
    togg= !togg;
    //
    //
    IFS0CLR = 0x80000;// Clear the T4 interrupt flag Bit 19
    //
  }
}

void initTmr(){
  // 
  T4CON=0x0; //Stop timer and clear registers
  T4CONSET = 0x0010; // set prescalar 1:2 ox60 to experiment
  TMR4 = 0x0; //Clear Timer 4 register
  PR4 = T1_TICK ; //0x17; // set timer to 23 
  IFS0CLR = 0x80000;// Clear the T4 interrupt flag Bit 19
  IPC4SET = 0x00000016;// Interrupt priority 5, 2
  IEC0SET = 0x80000;// Enable T4 interrupt Bit 19
  T4CONSET = 0x8000;// Enable Timer4  
}
void sine (){
  uint16_t i;
  for(i=0;i<WAVE_SAMPLES;i++){
    b = 2047*sin((2*PI/WAVE_SAMPLES)*i);
    b+=2047;
    sineData [i]=b;
  }
}