Watchdog question

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Blipp-Blopp-Bob
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Posted by Blipp-Blopp-Bob: Mon. Apr 19, 2010 - 01:52 PM
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Hi!

Im using the ATTiny861 and I would like to use the watchdogtimer.
Its the first time I use it but I've checked it up and I know how to enable:
wdt_enable(WDTO_8S);
and reset:
wdt_reset();

Now to the problem. 8s is max but I want to be able to set it to 10, 15 or 20s.
I was thinking of using ISR() and a globel uint8_t to keep track of how many times the watchdog had reached 5s.
And when the settings (10s, 15s, 20s) have been reached then I want to reboot my system. Any suggestion on how I could do this. Or if you have a better solution pls post a code and some text to explaine. Would really like to learn. :)

Best regards
BBB

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Tools, Atmel Studio (AVR-related)
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Gold Markclawson
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Posted by clawson: Mon. Apr 19, 2010 - 02:07 PM
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You don't necessarily need a timer to have a long period to be able to do something every 10/15/20s. Say you just run a "normal" timer 0/1/2 so it has an overflow interrupt every 25ms. Then to have something occur every 15 seconds you just have the interrupt increment a counter until it reaches 40 * 15 = 600, then do (or at least trigger) the 15 second work and reset the counter. (40 = 1/0.025)

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Blipp-Blopp-Bob
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Posted by Blipp-Blopp-Bob: Tue. Apr 20, 2010 - 06:26 AM
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I wanted to use the watchdog because after the XXseconds the µController should reset. This because I want the varibles to be rebooted and I've made a "sleep state" which the µController starts in. The sleep state is waiting for an approach-signal and after that the µController starts it's main purpose.
So by the using the watchdog and reseting the sowftware will work lika setting the µController back in stand-by mode when nothing have happend.

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Blipp-Blopp-Bob
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Posted by Blipp-Blopp-Bob: Tue. Apr 20, 2010 - 07:19 AM
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Is there any function like reset() or reboot() that one could call upon to reset the µController?

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Gold Markclawson
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Posted by clawson: Tue. Apr 20, 2010 - 08:48 AM
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Quote:

Is there any function like reset() or reboot() that one could call upon to reset the µController?

Well that's where the watchdog DOES come in useful - just enable it with the shortest possible timeout then tight loop. The other way is to drive the _RESET pin by another PORT pin.

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Blipp-Blopp-Bob
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Posted by Blipp-Blopp-Bob: Tue. Apr 20, 2010 - 09:28 AM
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clawson wrote:
Quote:

Is there any function like reset() or reboot() that one could call upon to reset the µController?

Well that's where the watchdog DOES come in useful - just enable it with the shortest possible timeout then tight loop. The other way is to drive the _RESET pin by another PORT pin.

Hehe, I have already solved the problem like that.
Thanks any way for at quick and good answer.

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