Example watchdog

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This is a guide to the watchdog C example project included in the EMAC OE SDK.

A watchdog timer (WDT) is a hardware circuit that can reset the computer system in case of a software fault. This is an example test for the Linux watchdog API.

The watchdog project builds one executable: watchdog-test.

Opening, Building and Uploading the Project Files

stubbooo

Usage and Behavior

A watchdog timer is a hardware circuit that can reset the computer system in case of a software fault. The watchdog-test application can enable, disable, activate, configure and interrupt the watchdog timer.



watchdog

Hardware Requirements

fof ofoo

watchdog Usage

./watchdog-test [-det]
  • d Disable the watchdog card.
  • -e" to enable the watchdog card
  • -s set the watchdog timeout

Usage Example. Activating watchdog with a periodic interrupt

This will activate watchdog and initiate a periodic interrupt to keep it from timing out.

root@som9g20:/tmp# ./watchdog-test 
Watchdog Ticking Away!

We have activated watchdog and now it is counting down to computer reset - or rather it would be if we didn't keep resetting it's timer. That's the LED on the SoM blinking at about 1 Hz. Every second watchdog-test is sending an IOCTL to the watchdog driver, which in turn ticks watchdog to reset its internal timer so it doesn't timeout and trigger a system reset.

Now we will stop interrupting watchdog and let it trigger a computer reset. Hit CTRL-C.

...and the system resets.

Usage Example. Disabling watchdog

root@som9g20:/tmp# ./watchdog-test -d
Watchdog card disabled.

...and the program exits normally.

Usage Example. Enabling watchdog

This will enable and activate watchdog but it won't perform a periodic timeout interrupt (see the first usage example). So when you run it the program activates watchdog and then watchdog resets the system.

root@som9g20:/tmp# ./watchdog-test -e
Watchdog card enabled.

...and the system resets.

Usage Example. Setting watchdog timeout

This will activate watchdog and set it to timeout in 5 seconds.

root@som9g20:/tmp# ./watchdog-test -t
Watchdog timeout set to 5 seconds!

...the program exits normally, then 5 seconds elapse, and then the system resets.

Summary

The watchdog C example project demonstrates how to use the Watchdog Timer. We provide examples of how to enable, disable, activate, configure and interrupt the watchdog hardware circuit.