Example watchdog
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
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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.
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Activating watchdog invokes system reset (after timeout) |
Hardware Requirements
watchdog will run on any system for which it can be compiled and implements the standard Linux watchdog API.
watchdog Usage
./watchdog-test [-det]
- -d
- Disable watchdog.
- -e
- Enable watchdog.
- -t
- Set the watchdog timeout (to a value specified in code. Default is five seconds).
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, above). 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.
