Difference between revisions of "Example watchdog"
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Revision as of 10:42, 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.
Contents
Opening, Building and Uploading the Project Files
stubbooo
Usage and Behavior
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. Letting watchdog reset the system
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 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.
