Example watchdog

TODO: {{#todo:Review(01.02.14-15:25->JG+)|Jgreene|oe 4,oe 5,jg,md,Review}}

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

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

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 the watchdog

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

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

...and the system resets.