Can anyone suggest the difference between these two programs

Using Arduino Project Guidance
1 
#include<avr/sleep.h>

ISR(TIMER1_OVF_vect)
{
  static boolean state=false;
  Serial.println("Woke from sleep mode");
  if(state)
  {
    state=false;
    digitalWrite(13,LOW);
  }
  else
  {
    state=true;
    digitalWrite(13,HIGH);
  }
  TIFR1=0x00;
}

void setup()
{
  pinMode(13,OUTPUT);
  TCCR1A=0x00;
  TCCR1B=0x05;
  TIFR1=0x00;
  TIMSK1=0x01;
  Serial.begin(9600);
  MCUCR|=0xF0;
}

void loop()
{
  Serial.println("Going to sleep mode");
  sleep_cpu();
}



and



#include<avr/sleep.h>

ISR(TIMER1_OVF_vect)
{
  static boolean state=false;
  //Serial.println("Woke from sleep mode");
  if(state)
  {
    state=false;
    digitalWrite(13,LOW);
  }
  else
  {
    state=true;
    digitalWrite(13,HIGH);
  }
  TIFR1=0x00;
}

void setup()
{
  pinMode(13,OUTPUT);
  TCCR1A=0x00;
  TCCR1B=0x05;
  TIFR1=0x00;
  TIMSK1=0x01;
//  Serial.begin(9600);
  MCUCR|=0xF0;
}

void loop()
{
//  Serial.println("Going to sleep mode");
  sleep_cpu();
}

actually the first program doesnt work in sleep mode, it always prints the data "going to sleep mode" and prints "woke from sleep mode" after every 4 seconds..
I'm finding it hard to figure out why its not working when i use serial port communications..

2

I can't yet see the differences, but I can see what is the same - neither is posted in a code box.

3

The second one has Serial.println("Going to sleep mode"); commented out.

Btw, there are programs, like the diff command in Linux and Unixes, which show the differences between two files.

4

Guys i know the character wise difference between them..
I want to know why commented out program goes to sleep mode, and why uncommented one doesnt go to sleep mode.

5

Perhaps the "tx register empty" signal wakes the processor shortly after it is put to sleep.

6

Serial data sending in an ISR is not a good idea. It takes too long.

In the second code, you still have a call to Serial.print() although Serial.begin() is commented out. Why?

7

PaulS:
Serial data sending in an ISR is not a good idea. It takes too long.

In the second code, you still have a call to Serial.print() although Serial.begin() is commented out. Why?

Sorry for that..
programming mistake.

8

Thanks for all the replies...
Though i couldnt figure out how to use the above with serial port enabled and working..:frowning:
I am able to use WDT timer for this purpose...:slight_smile: :slight_smile: