Mega 2560 - millis() and 16-bit timer counter interrupts

Projects Programming
1

Hi All,

I'm trying to get a 16-bit timer counter running, with interrupts on a Mega 2560 without destroying millis().

I've tried all 16-bit timer counters (1,3,4,5) with the following code, and all destroy millis() and make it run slow.

Any suggestions?

void timers_and_pwm_setup(){
  noInterrupts();
  //SETUP INTERRUPT FOR INPUT AVERAGING ///////////////////
  //set timer2 interrupt at 16mS (62.5Hz)
  TCCR4A = B00000000;// set entire TCCR4A register to 0
  TCCR4B = B00000000;// set entire TCCR4B register to 0
  TCNT4 = 33535;
  TCCR4B = B00000010;// Set CLK prescaler of div8. 16MHz / 8 = 2MHz
  // enable overflow interrupt
  TIMSK4 = B00000001;    
  interrupts();
  }

and the ISR...

ISR(TIMER4_OVF_vect)
  {
  TCNT4 = 33535;
  //MORE CODE HERE...
  }

Both my 8-bit timer counters are already in use, and I need another with an interrupt enabled.

I should also mention I've got a WDT enabled, and quite a bit of code in my setup script. It's definitely not rebooting.

Bevan

2

Please post your full code. If your ISR is running too long, it influences all other interrupt based functionality. ISR's have to be short.

1 Like
3

Thanks MicroBahner,

This is exactly what was causing it. I was spitting some data out via UART in the interrupt, and it was causing the fore-mentioned problems.

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4

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