Mini IR Theremin

The Software
           The software running on the PIC contains 3 main portions:
    -A/D Input Interrupt
    -Timer Output Interrupt
    -Main Switch Function


The A/D Input Interrupt is a quick and simple low priority interrupt. The timer interrupt takes high priority because we want the speaker sound to be crystal clear.

Low and High Priority Interrupts

void InterruptHandlerHigh()
{
   if(INTCONbits.TMR0IF)
   {
     //Reset The Timer Value
   WriteTimer0( timer0_val );
     //If a valid 'note' is stored in timer0_val, Play It!
      if( timer0_val <= 0xFB55 && timer0_val >= 0xED56){
      sound_state = (sound_state ^ 0xFF) & new_volume;
      PORTD = sound_state;
      }
   INTCONbits.TMR0IF = 0;
   }
INTCONbits.GIEH = 1; //Re-enable all high priority interrupts
return;
}
void InterruptHandlerLow()
{
   if(PIR1bits.ADIF == 1){
      //AD Interrupt Triggered, Read The Value
   ad_val = ReadADC();
      //Set AD Value Ready
   ad_ready = 1;
   PIR1bits.ADIF = 0;
   }
INTCONbits.GIEL = 1; //Re-enable all low priority interrupts
return;
}

           The code above should be straight forward. The interrupts are not suppose to be processor hogs, they should be quick, simple and as short as possible.

Main Switch

..
...
ConvertADC(); // Start conversion
if(ad_ready == 1){
    //Calculate The Distance Using The Formula
 result = pow(3027.4/ad_val,1.2134);
    //Convert The Distance From Float to Integer
 distance = (int) result;
    //Clear AD_ready because we used the ADC result
 ad_ready = 0;
    //Change The Timer0_val according to distance
 switch(distance){
   //C4
   case 11 :
   case 12 :
   case 13 :
   case 14 :
   case 15 : timer0_val = 0xED56;
   break;
   ..
   ...
   ....
   ..
   //C5
   case 46 :
   case 47 :
   case 48 :
   case 49 :
   case 50 : timer0_val = 0xF6AB;
   break;
   default : timer0_val = 0x0000;
 }
}
Delay10KTCYx(1);
...
..

           The main function of this project tells the A/D converters to start and then computes the distance away the object is from the sensor and passes that value to a switch statement. Depending on what value timer0_val gets updated with tells the timer0 to play a different tone on PORTD. This process happens over and over forever until the batteries die.