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[on:]

I'm doing register level programming in arduino.The goal is to write my own delay logic using timers.Here is the code

Code:

#include<avr/io.h>

int main()
{
  DDRB=(1<<PORTB5);
  TCCR1B=(1<<CS12);
  while(1)
  {
    if(TCNT1>=31250)
    {
      PORTB^=(1<<PORTB5);
      TCNT1=0;
    }
  }
  return 0;
}

The above program is for arduino to introduce delay without using delay function and its working alright.But have a look at the code below.

Code:

#include<avr/io.h>

void setup()
{
   DDRB=(1<<PORTB5);
   TCCR1B=(1<<CS12);
}

void loop()
{
   if(TCNT1>=31250)
   {
      PORTB^=(1<<PORTB5);
      TCNT1=0;
   }
}

When I write it this way,the program is getting compiled but there is no blinking in arduino. What might be the problem?

[Reply #1 on:]

Could it be that the PWM output code (analogWrite()) is configuring Timer1?  Perhaps you have to initialize more than one of the Timer1 registers.

You may also want to try:

Code:

      PINB = (1<<PORTB5);

That toggles the pin without needing the XOR operator.  The PINx register will toggle any bits written as 1.

[Reply #2 on:]

The arduino's main function calls "init()" before setup(). init() is defined in your arduino directory under:
{arduino}/hardware/arduino/cores/arduino/wiring.c

See if it is messing with any of the same registers that you are.