As soon as you switch from using main/while to setup/loop, that is the signal for the IDE to attach all the 'Arduino' background configuration files which include pin/port descriptors, setup for PWM and configuration of timer0 for millis() and delay() and others. You can still use the IDE with main/while and should be able to port code directly. I do most of my work with Notepad++ and a separate avr-gcc compiler, only to copy it into the IDE for the convenience of bootloading and final tweaking. I never use setup/loop.
Differences in operation are likely to be inside your TMR0_init() function.
Instead of just configure the timer from its system-reset state, your code will also have to "undo" any of the configuration that the Arduino core has already applied.
When you define your own main(), it overrides the core library's main. In this case, the important thing about that is init() never gets called.
Very important point.
The importance of init() however, is subject to the users' desire to gain control over system resources. In a beginner/learning mode it makes perfect sense as many of the peripherals would be unavailable without being otherwise configured. If you want complete control though, you would need to undo what init() does and/or reconfigure each peripheral independently. This means actually having to learn how to program the chip as opposed to simply attaching a cart-load of libraries and abstracting the low-level functionality. Depends really, on just what it is you want to learn. For many, the abstraction is sufficient. For others its a nuisance.
First of all I found this dude controlling all 3 timers in Arduino sketch, I ran his code and it's working perfectly, except at very high speed there's little timing not very accurate. Anyway this is the code:
//timer interrupts
//by Amanda Ghassaei
//June 2012
//https://www.instructables.com/id/Arduino-Timer-Interrupts/
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
*/
//timer setup for timer0, timer1, and timer2.
//For arduino uno or any board with ATMEL 328/168.. diecimila, duemilanove, lilypad, nano, mini...
//this code will enable all three arduino timer interrupts.
//timer0 will interrupt at 2kHz
//timer1 will interrupt at 1Hz
//timer2 will interrupt at 8kHz
//storage variables
boolean toggle0 = 0;
boolean toggle1 = 0;
boolean toggle2 = 0;
void setup(){
//set pins as outputs
pinMode(11, OUTPUT);
pinMode(13, OUTPUT);
pinMode(12, OUTPUT);
cli();//stop interrupts
//set timer0 interrupt at 2kHz
TCCR0A = 0;// set entire TCCR2A register to 0
TCCR0B = 0;// same for TCCR2B
TCNT0 = 0;//initialize counter value to 0
// set compare match register for 2khz increments
OCR0A = 255;// = (16*10^6) / (2000*64) - 1 (must be <256)
// turn on CTC mode
TCCR0A |= (1 << WGM01);
// Set CS01 and CS00 bits for 64 prescaler
TCCR0B |= (1 << CS02)/*|(1 << CS01)*/|(1 << CS00);
// enable timer compare interrupt
TIMSK0 |= (1 << OCIE0A);
//set timer1 interrupt at 1Hz
TCCR1A = 0;// set entire TCCR1A register to 0
TCCR1B = 0;// same for TCCR1B
TCNT1 = 0;//initialize counter value to 0
// set compare match register for 1hz increments
OCR1A = 1564;// = (16*10^6) / (1*1024) - 1 (must be <65536)
// turn on CTC mode
TCCR1B |= (1 << WGM12);
// Set CS12 and CS10 bits for 1024 prescaler
TCCR1B |= (1 << CS12) /*|(1 << CS10)*/;
// enable timer compare interrupt
TIMSK1 |= (1 << OCIE1A);
//set timer2 interrupt at 8kHz
TCCR2A = 0;// set entire TCCR2A register to 0
TCCR2B = 0;// same for TCCR2B
TCNT2 = 0;//initialize counter value to 0
// set compare match register for 8khz increments
OCR2A = 249;// = (16*10^6) / (8000*8) - 1 (must be <256)
// turn on CTC mode
TCCR2A |= (1 << WGM21);
// Set CS21 bit for 8 prescaler
TCCR2B |= (1 << CS22)|(1 << CS21)|(1 << CS20);
// enable timer compare interrupt
TIMSK2 |= (1 << OCIE2A);
sei();//allow interrupts
}//end setup
ISR(TIMER0_COMPA_vect){//timer0 interrupt 2kHz toggles pin 8
//generates pulse wave of frequency 2kHz/2 = 1kHz (takes two cycles for full wave- toggle high then toggle low)
if (toggle0){
digitalWrite(13,HIGH);
toggle0 = 0;
}
else{
digitalWrite(13,LOW);
toggle0 = 1;
}
}
ISR(TIMER1_COMPA_vect){//timer1 interrupt 1Hz toggles pin 13 (LED)
//generates pulse wave of frequency 1Hz/2 = 0.5kHz (takes two cycles for full wave- toggle high then toggle low)
if (toggle1){
digitalWrite(12,HIGH);
toggle1 = 0;
}
else{
digitalWrite(12,LOW);
toggle1 = 1;
}
}
ISR(TIMER2_COMPA_vect){//timer2 interrupt 8kHz toggles pin 9
//generates pulse wave of frequency 8kHz/2 = 4kHz (takes two cycles for full wave- toggle high then toggle low)
if (toggle2){
digitalWrite(11,HIGH);
toggle2 = 0;
}
else{
digitalWrite(11,LOW);
toggle2 = 1;
}
}
void loop(){
//do other things here
}
This is the logic analyzer testing:
westfw:
TMR0_init();
Differences in operation are likely to be inside your TMR0_init() function.
Instead of just configure the timer from its system-reset state,
wolfrose:
What I understood is that the first init() should call any Arduino configurations.
It calls this:
wolfrose:
This way anything I put in setup() should overwrite what Arduino did. Am I correct?
If by "write", you mean writing to registers, yes. init() is called once when the board first starts up, then setup() is called, then loop() is called over and over again forever.
{