Watchdog timer Question???

Forum 2005-2010 (read only) Software Interfacing
1

I would like to set a Watchdog timer to reset my Arduino Atmega168 microcontroller, if I do not pat the dog( prevent the Watchdog timer from expiring and reseting my Atmega168) every 2 minutes. However, I am not sure how to do this, all I found is the starting point of code below from a google search:

Example Code (GCC) Resetting the AVR every 30mS:

#include <avr/io.h>
#include <avr/wdt.h>

int main(void)
{
wdt_enable(WDTO_30MS);
while(1) {};
}

Alternatively you can create a macro:

Code:

#include <avr/io.h>
#include <avr/wdt.h>

#define Reset_AVR() wdt_enable(WDTO_30MS); while(1) {}

int main(void)
{
Reset_AVR();
}

Thanks for any help
Rico

2

you could try it with something like this:

#include <avr/io.h>
#include <avr/wdt.h>

void setup(){
  wdt_enable(WDTO_30MS);
}

If you want to have a look, hardware\tools\avr\avr\include\avr\wdt.h has the defines for different watchdog delays. The longest delay defined is 2 seconds. I think the ATmega168 chip used in the arduino can support up to 8 seconds

3

#include <avr/io.h>
#include <avr/wdt.h>

void setup(){
wdt_enable(WDTO_30MS);
}

MEM, so the above code takes care of everything meaning I do not need to pat the dog every 30 milliseconds? It is all done by the calling function.
If so, that is great.
Thanks
For the help
Rico

4

http://linux.die.net/man/3/wdt_enable
http://www.nongnu.org/avr-libc/user-manual/group__avr__watchdog.html

--> wdt_reset()

p.s. google ... and so on

5

I answered rico via pm, this was my response:

the code posted sets the watchtog for the given timeout period, you still need to pat the dog.

To do that, you must call wdt_reset();
When the watchdog timer is enabled, a call to this instruction is required before the timer expires, otherwise a watchdog-initiated device reset will occur.

There is not yet an arduino friendly version of this code so you will need to do a little research, there looks to be quite a good document here: http://www.atmel.com/dyn/resources/prod_documents/doc2551.pdf

I have not used the watchdog on the Arduino so don't have any more info than that.

6

I tried the following code below, trying to trigger the watchdog timer using a delay of 10 seconds and the microcontroller got stuck in an infinite reset loop. I thought it should reset and turn the LED on for another 10 seconds but not the case?? Not sure why???? Can anyone help?
Thanks
RB :frowning:

#include <avr/io.h>
#include <avr/wdt.h>

int ledPin = 5;

void setup()
{
wdt_enable(WDTO_8S);
pinMode(ledPin, OUTPUT);
}

void loop()
{
digitalWrite(ledPin, HIGH); // sets the LED on
delay(10000); // waits for a 10 seconds
digitalWrite(ledPin, LOW); // sets the LED off
delay(250); // waits
wdt_reset();
}

7

The dog is impatient !

BTW, if you just want to make the led blink, you don't need the watchdog at all.

ruff ruff

8

I tried adding the MCUSR=0; like the data sheet said and still not working??? :frowning:

#include <avr/io.h>
#include <avr/wdt.h>

int ledPin = 5;

void setup()
{
MCUSR=0;
wdt_enable(WDTO_8S);
pinMode(ledPin, OUTPUT);
}

void loop()
{
digitalWrite(ledPin, HIGH); // sets the LED on
delay(10000); // waits for a 10 seconds
digitalWrite(ledPin, LOW); // sets the LED off
delay(250); // waits
wdt_reset();
}

9

You set the watchdog timer timeout to 8 seconds, then you wait for more than 10 seconds, and then you pat the dog with wdt_reset().

As the 8 < 10 your code never gets beyond delay(10000).

10

Yes, I know this, the problem is the watchdog timer never comes out of the reset loop. I spoke with another fellow and he said the problem is with the bootloader. However, I think ladyada's bootloader will sovle this problem. I will post the results next week!

11

Hey, Just want everybody to know that the watchdog timer works perfect with ladyada's bootloader from adafruit.com

12

I tried the code up there, and now i can`t upload coz the dog keeps barking. LED 13 keeps blinking all the time. Panic mode: ON.
Any help plz. THX

13

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1271245150/2#2

14

I make the watchdog timer 30MS.....Darn it so hard to try what u said.
ANY other option? =(

15

Miracles does happens, some delay happened and i can upload blink. fiuh...thx.