Self-waking PIC

Apr 05, 2005 4 Replies
P

Hi all,



Is there anyway that a PIC in sleep mode can wake-up periodically by way of an internal mechanism (say, every 30 seconds), perform a short routine and then re-enter Sleep again?



I'm using a 16F505, but this has no interrupts so I was wondering if I could use the internal timer to implement this function? I know the wake-up on input change would suit but this would mean adding an external timer and the loss of an I/O pin.



If this is not possible with the 505, is it possible with any other PIC and if so, do I still have to externally generate an interrupt every 30 seconds?



Thanks for any help, Simon



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W

Hi Simon,

PigPOg schrieb:

Enable the watchdog, setup the wdt prescaler as you prefer. Every watchdog trigger puts the device out of reset. You can determine a WDT reset from a power-on-reset by using some STATUS bits provided. I have done that, works great. If you like some more details -> PM me (see below).

HTH Wolfgang

From-address is Spam trap Use: wolfgang (dot) mahringer (at) sbg (dot) at
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P

Wolfgang,

Thank you for the suggestion - I have no idea why I didn't think of this! It's the perfect solution for me.

Thanks once again, kind regards, Simon

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M

If you need really really low power draw, look at the nanopower devices like the

16F636 - these have a watchdog postscaler that allows WDT periods up to a few minutes, and have much lower watchdog current - about 3uA
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P

the 16F636 - these have

much lower watchdog

I'll follow that up - thanks Mike.

Simon

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