> This is an ARM SBC, it has no BMC and AFAIK no watchdog or other timer
> that can be programmed to cause a reboot, if you are aware of anything
> like that on ARM SBC:s let me know?
Watchdog timers are a somewhat common feature for SoCs designed for embedded
use. Look up the reference manual for your device, it might have one. If not,
you could implement your own as long as you can toggle a GPIO line. Here's a
device from Maxim Integrated that could work:
It ought to be fairly simple to wire up the watchdog input to a GPIO line and
the output to your RESET input, and it can be configured to have a long delay,
which is probably a good idea because it may take a while before you're booted
up enough to start sending heartbeat pulses.