Extending edgertronic capabilities - Hardware watchdog timer

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Background

This feature was initially scheduled for V2.1 but has been rescheduled for v2.3.


The DM368 processor used in the edgertronic camera supports a hardware watchdog timer. The purpose of a hardware watchdog timer is to perform a hardware reset if the software crashes.

Watchdog timer support

Support to use the hardware watchdog timer is done using the user added URLs edgertronic SDK mechanism. Simple copy the app_ext_wdt.py file from http://10.11.12.13/static/sdk/app_ext and save it in the root directory of your removable storage device, then power on the camera.

The hardware watchdog timer is enabled by browsing to

http://10.11.12.13/wdt_enable URL.

replacing 10.11.12.13 with your camera's IP address as necessary.

Watchdog URLs

/wdt_enable Enable hardware watchdog timer and python logic to service the watchdog timer.
/wdt_counter Returns a JSON encoded count of how many times the camera's hardware watchdog timer has reset the processor since power on.
/wdt_force_reset Test feature which causes the processor to reset the camera in around 60 seconds.

Watchdog timer functional description

The DM368 hardware watchdog timer is made available to user space via the /dev/watchdog device file. Simply holding an open file handle to the /dev/watchdog device file enable the hardware watchdog timer. Simply writing a byte of data to the open file handle services the hardware watchdog timer. The DM368 hardware watchdog timer will reset the processor if more than 56 seconds goes by without the hardware watchdog timer being service.

When /wdt_enable is invoked, the /dev/watchdog device file is opened and a periodic software timer is enabled to service the hardware watchdog timer every 10 seconds. If something causes the periodic software timer to fail to run, the hardware watchdog timer will cause the camera to reboot.




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