Convert Timer2 on Atmega328P interrupt to Timer4 on Atmega32u4

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1

Hi, I have this code for playing audio from pin D3 on an Arduino Uno:

#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif
//

void Init_Register() {

  // Set up Timer 2 to do pulse width modulation on the speaker
  // pin.
  pinMode(3, OUTPUT);

  //use internal clock
  cbi(ASSR,EXCLK);    //disable external clock
  cbi(ASSR,AS2);      //clock timers from internal clock

  //Fast PWM mode  
  sbi(TCCR2A,WGM20);  //TOV flag set on max
  sbi(TCCR2A,WGM21);  //Update OCRx at bottom
  cbi(TCCR2B,WGM22);  //Top = 0xFF
 
  //Set non-inverting PWM on OC2B pin
  cbi(TCCR2A,COM2B0);
  sbi(TCCR2A,COM2B1);
  //set normal operation on OC2A pin
  cbi(TCCR2A,COM2A0);
  cbi(TCCR2A,COM2A1);
  
  //no prescaler
  sbi(TCCR2B,CS20);
  cbi(TCCR2B,CS21);
  cbi(TCCR2B,CS22);
  
  // Set Timer 1 to update sample on interrupt

  cli();      //pause interrupts

  // Set CTC mode (Clear timer on compare match)
  cbi(TCCR1A,WGM10);
  cbi(TCCR1A,WGM11);
  sbi(TCCR1B,WGM12);
  cbi(TCCR1B,WGM13);

  //No prescaler
  sbi(TCCR1B,CS10);
  cbi(TCCR1B,CS11);
  cbi(TCCR1B,CS12);  

  // Set the compare register (OCR1A) initial value
  OCR1A = F_CPU/(440*WAVE_LEN);       //initialise with A=440hz.

  // Timer 1, output compare A match interrupt enable
  sbi(TIMSK1,OCIE1A);

  sei();    //start interrupts
  
  // faster ADC
  // uses div factor of 8.  standard arduino read is 128.
  sbi(ADCSRA,ADPS2) ;
  cbi(ADCSRA,ADPS1) ;
  sbi(ADCSRA,ADPS0) ;
  
}

I need to convert it so it uses Timer 4 on an Arduino Esplora (Atmega 32u4). Timer 4 has different parameters to Timer 2 (it's 10 not 8 bit for starters). I'm really struggling to convert this code to use Timer4. I don't even know if it's possible. Any help would be appreciated!! Here's my attempt so far:

#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif
//

void Init_Register() {

  // Set up Timer 2 to do pulse width modulation on the speaker
  // pin.
  pinMode(3, OUTPUT);

  //use internal clock
  //cbi(ASSR,EXCLK);    //disable external clock
  //cbi(ASSR,AS2);      //clock timers from internal clock

  //Fast PWM mode  
  cbi(TCCR4D,WGM40);  //TOV flag set on max
  cbi(TCCR4D,WGM41);  //Update OCRx at bottom
  sbi(TCCR4C,PWM4D);  //Top = 0xFF
 
  OCR4C = 255;
 
  //Set non-inverting PWM on OC2B pin
  cbi(TCCR4C,COM4D0);
  sbi(TCCR4C,COM4D1);
  //set normal operation on OC2A pin
  //cbi(TCCR2A,COM2A0);
  //cbi(TCCR2A,COM2A1);
  
  //no prescaler
  sbi(TCCR4B,CS40);
  cbi(TCCR4B,CS41);
  sbi(TCCR4B,CS42);
  cbi(TCCR4B,CS43);
  
  // Set Timer 1 to update sample on interrupt

  cli();      //pause interrupts

  // Set CTC mode (Clear timer on compare match)
  cbi(TCCR1A,WGM10);
  cbi(TCCR1A,WGM11);
  sbi(TCCR1B,WGM12);
  cbi(TCCR1B,WGM13);

  //No prescaler
  sbi(TCCR1B,CS10);
  cbi(TCCR1B,CS11);
  cbi(TCCR1B,CS12);  

  // Set the compare register (OCR1A) initial value
  OCR1A = F_CPU/(440*WAVE_LEN);       //initialise with A=440hz.

  // Timer 1, output compare A match interrupt enable
  sbi(TIMSK1,OCIE1A);

  sei();    //start interrupts
  
  // faster ADC
  // uses div factor of 8.  standard arduino read is 128.
  sbi(ADCSRA,ADPS2) ;
  cbi(ADCSRA,ADPS1) ;
  sbi(ADCSRA,ADPS0) ;
  
}
2

Bah IDIOT!! Stupid error!

pinMode(3, OUTPUT);

should be

pinMode(6, OUTPUT);

(Because Timer 4 uses pin D6). All sorted now :slight_smile: