Difference between revisions of "Example watchdog"
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This is a guide to the <code>watchdog</code> C example project included in the EMAC OE SDK. | This is a guide to the <code>watchdog</code> C example project included in the EMAC OE SDK. | ||
Revision as of 12:32, 3 January 2014
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.
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). 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.