Arduino CTC mode output not as expected

KlausST said:

Hi,

What hardware do you use? (Microcontroller, module ...)
What's the system clock frequency?

Klaus

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FenTrac said:

Try setting TCCR0A and TCCR0B to zero so you have everything at 0 to begin with.

Code:

void setup () {
  //Pin 6 (OC0A) is output
  pinMode(6, OUTPUT);
 
TCCR0B = 0;   // write 0 to timer 0 control registers
 TCCR0A = 0;
 
   // Load 79 to generate 100 kHz sq.wave
  OCR0A = 79;
   // Toggle OC0A on compare match, WGM 2 (CTC mode)
  TCCR0A = (1 << COM0A0) | (1 << WGM01);
  // Start the timer, no prescalar
  TCCR0B = (1 << CS00);
}

void loop() {

}

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FenTrac said:

Before my previous post, I ran your code on my Arduino and received the same 8 Mhz as you experienced. Starting with TCCR0A and TCCR0B zeroed, your code ran with the correct 100khz on pin 6. I suspect that the bootloader may cause the registers to be non zero to start with.
The low voltage you are experiencing and incorrect frequency, Is a separate issue. My arduino, is showing a 10 microsecond waveform with an amplitude of 4.8 volts at pin 6 on the scope.
Check for loading of the signal, probe settings (10x or 1x), and double check scope settings.
Maybe measure frequency with a mutimeter if you have one that will measure the expected signal.

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