External Hardware Watchdog Timer w/ a Photon

Hardware
1

Has anyone ever implemented an external watchdog timer for a particle Photon?

I’m in a situation where I’d like to supply a voltage to a circuit if the Photon itself becomes unstable. I was wondering if anyone has accomplished something similar with an external watchdog timer.

Thanks!

Chris

2

@casche, is the watchdog to reset the photon?

3

Hey @peekay123,

Ultimately yes, but I would also like to trip a relay just prior to the photon reseting.

4

I’ve done it with a PIC10F320, but an ATTiny would do the same. You just need to toggle an output pin every second or so on the photon which the watchdog reads on an interrupt to reset a countdown timer. If the timer expires, pull down the reset line and reset the timeout. It needs a time long enough for the photon to get started. The photon has this as a built-in function now, though.

5

@casche,

I have the same need. Here is my approach. Hope it is helpful.

Chip