OCR1A works for the timer interrupt, but OCR1B and OCR1C do not work. Why is this?

Other Hardware Audio
1

I am working on a WAV player, and the timer interrupt works with OCR1A, but it does not work with OCR1B or OCR1C. What could be the reason for this?

#include <SD.h>
#include <SPI.h>

#define SD_CS 53
#define SAMPLE_RATE 44.1e3

File root, wav;
unsigned char buf[6000];
volatile uint16_t playing_Index = 0;
volatile uint16_t write_Index = 3000;
volatile bool bufferFlag = false;
uint32_t dataSize;
uint16_t endTime;
volatile uint16_t audioSum = 0;

void setup() {
  SPI.setClockDivider(SPI_CLOCK_DIV2);
  SD.begin(SD_CS);
  initializeWav(0);
  initializePins();
  initializeTimerInterrupt();
}

void loop() {
  if (playing_Index >= 6000) {
    playing_Index = 0;
  } else if (playing_Index == 3000 || playing_Index == 0) {
    bufferFlag = false;
    wav.read(&buf[write_Index], 3000);
    write_Index = (write_Index == 0) ? 3000 : 0;
  }
}

void initializeWav(int8_t fileIndex) {
  playing_Index = 0;
  dataSize = 0;

  wav = SD.open("LIGHT441.WAV");
  wav.seek(40);
  for (uint8_t i = 0; i < 4; i++)
    dataSize += (uint32_t)wav.read() << (8 * i);
  endTime = dataSize / (4 * SAMPLE_RATE);

  wav.read(buf, 6000);
}

void initializePins() {
  DDRB |= 0b11111100;
  DDRH |= 0b01011000;
}

void initializeTimerInterrupt() {
  TCCR1A = 0;
  TCCR1B = 0;
  TCCR4B &= ~_BV(WGM43);
  TCCR4B |= _BV(WGM42);
  TCCR4A &= ~_BV(WGM41);
  TCCR4A |= _BV(WGM40);

  TCCR4A |= _BV(COM4A1);
  TCCR4A &= ~_BV(COM4A0);

  TCCR4A |= _BV(COM4B1);
  TCCR4A &= ~_BV(COM4B0);

  TCCR4B &= ~_BV(CS42);
  TCCR4B &= ~_BV(CS41);
  TCCR4B |= _BV(CS40);

  TCCR2B &= ~_BV(WGM22);
  TCCR2A |= _BV(WGM21);
  TCCR2A |= _BV(WGM20);

  TCCR2A |= _BV(COM2A1);
  TCCR2A &= ~_BV(COM2A0);

  TCCR2A |= _BV(COM2B1);
  TCCR2A &= ~_BV(COM2B0);

  TCCR2B &= ~_BV(CS22);
  TCCR2B &= ~_BV(CS21);
  TCCR2B |= _BV(CS20);

  TCCR1B &= ~_BV(WGM13);
  TCCR1B |= _BV(WGM12);
  TCCR1A &= ~_BV(WGM11);
  TCCR1A &= ~_BV(WGM10);

  TCCR1B &= ~_BV(CS12);
  TCCR1B &= ~_BV(CS11);
  TCCR1B |= _BV(CS10);

  OCR1C = 362;
  TCNT1 = 0;
  TIMSK1 |= _BV(OCIE1C);
  TIFR1 |= _BV(OCF1C);

  sei();
}


ISR(TIMER1_COMPC_vect) {
  audioSum = (buf[playing_Index] | (buf[playing_Index + 1] << 8)) + 0x8000;
  OCR2B = audioSum & 0x00FF;
  OCR2A = (audioSum & 0xFF00) >> 8;

  audioSum = (buf[playing_Index + 2] | (buf[playing_Index + 3] << 8))  + 0x8000;
  OCR4B = audioSum & 0x00FF;
  OCR4A = (audioSum & 0xFF00) >> 8;

  playing_Index += 4;
}
2

which arduino?

why are you posting in the audio category? ( compare match at OCR1C = 362 corresponds to a frequency of approximately 44.1 kHz so I guess it's audio related. if so what are you trying to achieve?)

Note also that If OCR1A , OCR1B, and OCR1C are enabled simultaneously, the microcontroller assigns priority to the interrupt vectors. OCR1A has the highest priority, followed by OCR1B, and then OCR1C.

This should not block OCR1C. from functioning, but if the ISR for OCR1A or OCR1B is consuming too much time it might delay or block OCR1C

(also you would need a critical section in the loop when you touch playing_Index as it's started with the ISR (and write_Index does not need to be volatile as it's not used in the ISR)

3

Use the correct interrupt name for the ISR, one ISR for each interrupt.

Check the datasheet for the details.