Timer0 Challenge

Projects Programming
1

I am not sure why, but the below code is not working.
I have tried to use timer0 of an Arduino Uno to delay time in milliseconds. Any help would be appreciated...

#include <avr/io.h>

//prototypes of functions
void delay_with_timer0();
void delay_generic(unsigned long);

void setup() {
  //initializing built in LED as output
  pinMode(LED_BUILTIN, OUTPUT);
  
  //enabling serial monitoring for debugging
  Serial.begin(9600);
}

void loop(){
  //turning built in LED on and off
  digitalWrite(LED_BUILTIN, HIGH);
  delay_generic(1000);
  digitalWrite(LED_BUILTIN, LOW);
  delay_generic(1000);
  Serial.print("SUCCESS\n");
}

void delay_with_timer0(){  
  //disable I-Flag
  cli();
  
  //initializing clock to zero
  TCNT0 = 0;
  
  //sets to normal mode
  TCCR0A = (0 << WGM00);
  TCCR0A = (0 << WGM01);
  TCCR0B = (0 << WGM02);
  
  //sets prescaler
  TCCR0B = (0 << CS00);
  TCCR0B = (1 << CS01);
  TCCR0B = (0 << CS02);
  
  //waiting for the overflow flag to be set
  while(true){
    if(TIFR0 |= (1 == TOV0)){
      break;
    }
  }
  
  //stops the clock
  TCCR0B = (0 << CS00);
  TCCR0B = (0 << CS01);
  TCCR0B = (0 << CS02);
  
  //clears TOV0 flag
  TIFR0 = (0 << TOV0);
  
  //enable I-Flag
  sei();
}

void delay_generic(unsigned long ms){
  //for loop that uses delay_with_timer0() function
  for(int i = 0; i < ms*250; i++){
    delay_with_timer0();
  }
}
2

"not working".... how? Please give details...

3

It does not delay time properly. I am not sure if it delays time at all besides due to the code itself being repeated numerous times.

4

Google a bit more, you are going about a perfectly reasonable experiment in an unconventional manner, at least I usually see

setup - configure all timer 0 control bits

use - examine and change only a few things

also odd and not what you want to do is mess with the interrupt stuff. No need whatsoever to accomplish simple timing using timer 0.

a7

5

Try looking at the TimerOne library

6

that looks pretty nonsensical. Surely you want

  if (TIFR0 & (1<<TOV0)) {
7

Use TCCR0B = 0<<CS02 | 1<<CS01 | 0<<CS00 instead

8

That is NOT how you set and clear individual bits in hardware registers. You need something like:

  // Initialize the registers to 0
  TCCR0A = 0;
  TCCR0B = 0;

  //sets to normal mode
  TCCR0A &= ~(1 << WGM00);  // Clear bit
  TCCR0A &= ~(1 << WGM01);  // Clear bit
  TCCR0B &= ~(1 << WGM02);  // Clear bit
  
  //sets prescaler
  TCCR0B &= ~(1 << CS00);  // Clear bit
  TCCR0B |=    (1 << CS01);  // Set bit
  TCCR0B &= ~(1 << CS02);  // Clear bit

Note: Once the registers are set to 0 there is no need to clear bits.

9

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