Why does timer ISR not execute?

Question

This is my code which I have written as a library

#include "avr/interrupt.h" 
#include "Arduino.h"
#include "AllTimer.h"
AllTimer::AllTimer()
{}
void AllTimer::dofun(void)
{
 //TIFR1 |= _BV(OCF1A);
 TCCR1B = 0X00;
 //TIFR1 = 0X01;
 digitalWrite(13,!digitalRead(13));
 Serial.print("I printed");
 TCNT1 = 0X0000;
 TCCR1B |= (1<<CS12) && (1<<CS10);
 //sei();
}
 void AllTimer::setTimer(void)
 {
 TCNT1 = 0x0000;
 TCCR1A = 0x00;
 TCCR1B = 0x00;
 TCCR1B |= (1<<CS12) && (1<<CS10);
 TIMSK1 |= (1<<TOIE1);
 sei();
 }
ISR (TIMER1_OVF_vect)
{
 AllTimer::dofun();
} 

Code in Arduino IDE:

 #include <AllTimer.h>
 AllTimer mytimer;
 void setup()
 {
 pinMode(13,OUTPUT);
 Serial.begin(9600);
 }
 void loop()
 { 
 mytimer.setTimer();
 //delay(200); 
 }

But I am not getting anything on the serial monitor. What is the error I have made?

• Gerben: Using Serial.print inside an ISR is asking for problems. Does the led blink? Also, there is no need to write TCCR1B and TCNT1 inside doFun.

Answer 1

The Arduino main() calls loop() continuously, in a tight loop. Thus your AllTimer::setTimer() is called continuously, and each time it resets the counter (TCNT1 = 0x0000;). Thus the counter can never overflow.

• Gerben: So put mytimer.setTimer(); inside setup instead of loop.
• Sim Son: also, in TCCR1B |= (1<<CS12) && (1<<CS10); shouldn't it be | instead of the logic &&?
• Edgar Bonet: @SimSon: Indeed! I hadn't spotted that. Good catch.