Watchdog Timer for the Raspberry Pi

RE: Watchdog Timer for the Raspberry Pi

roetske — Thu, 05 Jan 2017 16:53:11 GMT

Hello found your hardware schematic watchdog was looking for this for extra protection io control.

When you control eg heater with relay trough raspberry control. Extra safety is never bad. I like your control with pulse. However reading other comments , instead of resetting pi.

Catch via input in rasp (output from your timer) running in separate program fault from to restart processes or reboot .

for io control Why not cutoff output or supply to output using your schematic?

If your rasp is still frozen at least your outputs are disabled.

If you use different powersupply for io your setup with 555 timer is excellent to cutoff power to all active outputs. eg heater control rasp freezes outputs stay high. Not a situation that we want.

RE: Watchdog Timer for the Raspberry Pi

Former Member — Wed, 27 Jul 2016 17:26:48 GMT

This circuit looks very good ! And the function is not obscured by too much documentation and tons of sw code.

While I agree, there should be no sw-error left, ;-) : this watchdog should catch any remaining error.

Good design !

(One improvement would be very nice : Watchdog get's active only after the first trigger pulse. Would allow to make it's use optional.)

RE: Watchdog Timer for the Raspberry Pi

shabaz — Tue, 19 Jul 2016 11:29:27 GMT

Like all PCs the Raspberry Pi is likley to hang up during operation.

Hi Seggy,

Just to flesh out things a bit, perhaps an application could be likely to hang, generally the Linux kernel is not likely to hang unless there is a very severe issue like a build issue, hardware fault or power related issue.

It is worth mentioning that if the board ever does lock up, this should be investigated; because for the hardware watchdog to have to ever take action on a Linux platform is "severe".

Possible reasons could be a poor power supply perhaps, or bad cooling strategy, and for these the hardware watchdog action is like a sticking plaster and does not fix the underlying issue(s).

The underlying issues should therefore be resolved if the watchdog timer actually has to ever take action.

Finally, if users are experiencing application hangs then these do not require a hardware watchdog timer.