Friday, September 25, 2009

Retu watchdog turning off N810

Some days ago, using flasher, I decided to enable the R&D mode flag 'no-retu-wd', in order to disable watchdog on retu, using the following command:

$ flasher --set-rd-flags=no-retu-wd

In certain circumstances, like: excessive CPU usage, important process crasher, system lock up - hardware and software watchdogs/lifeguards reboots the device.

Retu is a custom ASIC chip that includes (at least) pseudo real-time clock control, power button control and a watchdog timer. On N810, there is a watchdog on the retu chip connected via cbus.

In fact, retu wd cannot be disabled due is controlled only by hardware means (resistance on a specific pin).

Anyway, if you try the command I mentioned above, N810 always turn off just after some (maybe 63) seconds after initialized.

So, avoid to try to disable the watchdog on retu, or your N810 will be turned off by its watchdog :) If you already disabled it, type the following command to revert the effects of 'disabling' retu wd:

$ flasher --clear-rd-flags=no-retu-wd

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