Regarding watchdog, there is a hardware watchdog in the processor, but it is disabled by default. Enabling it requires a minor modification to the at91bootstrap code and passing the proper parameters to the linux watchdog driver (at91sam9_wdt). There is currently no support in the U-Boot version we are using the for the watchdog, however. This means anything done in U-Boot has to be done quickly before the watchdog resets (16 seconds by default).

If you are interested in this, I can provide more detailed information. The U-Boot lack of support is the biggest limitation currently. Hopefully this can be resolved in a future update.

Regarding ppp, you have two options that come to mind:

1. You can use ppp with the ‘persist’ option. This makes pppd try to keep the connection up even if it goes down periodically.

2. You can use ppp without the persist option and write your own script to act as a ppp watchdog. When the connection goes down, pppd will no longer be running. You could check for the existence of pppd and if it is down, reset the modem (if desired) and then start pppd again.

If you want to enable the hardware watchdog, you can edit the following bbappend file and uncomment the line that brings in the watchdog patch. Then build the new bootstrap and flash it in.

http://git.multitech.net/cgi-bin/cgit.cgi/corecdp.git/tree/multitech/recipes/at91bootstrap/at91bootstrap_2.13.bbappend

# uncomment to enable watchdog in bootstrap
#SRC_URI += ” file://at91bootstrap-2.13-enable-watchdog.patch”

I check this Watchdog U-Boot driver on github:
https://github.com/lentinj/u-boot/blob/master/drivers/watchdog/at91sam9_wdt.c

Any idea how implement this?

• This reply was modified 8 years, 12 months ago by Herraiz Stéphane.