Watchdog

[lpcware]

Content originally posted in LPCWare by PhilYoung on Wed Sep 05 08:34:39 MST 2012
I have a boot loader that manages images, updates images over a network, and runs the most up to date image after validation, on entry it sets the watchdog and if the app if valid restores the device to reset state and enters the app.
When the app is executed it run fine so long as it calls the watchdog reset function periodically.

To test re-entry to the boot loader I disabled the watchdog reset code in the app, now when the watchdog expires the boot loader does not execute.

The device is reset by a wdog timeout, but presumably the embedded rom loader is called again to remap the shadow area, init the emc, and enter the boot loader as though a normal system reset had occured.

It's not clear from the documentation if the rom loader takes different action after a wdog reset, or if it can even detect that it occurred.

I'm after any suggestions as to why a program that boots and runs normally will not restart normally when a wdog reset occurs.

[thiagop]

We are experiencing the very same fault here, but on the LPC4357.

After a Watchdog Reset, the chip goes to that ROM address and never recovers, only after a hardware reset it will come back to life.

Is there any workaround or fix for this? The absense of Watchdog is not accepted by our application.

Thx

[Carlos_Mendoza]

Hi Thiago,

Could you check the state of the pin P2_7 after the watchdog reset? is recommended to provide external hardware (a pull-up resistor or other device) to put the pin in a defined state.

Thanks in advance!

Best Regards,

Carlos Mendoza

Technical Support Engineer

[lpcware]

Content originally posted in LPCWare by PhilYoung on Wed Sep 05 14:05:54 MST 2012
looks like there is a bug in the LPC4330 boot rom.

booting from external flash then letting the wdog generate a reset does not restart the application.

connecting a debugger after this occurs the CPU is stuck in the boot rom at 0x1040683A, where it's polling the auto baud register.

Since the jumpers were set to boot from flash, that's how the system was started, the boot rom should have gone back to the flash after the watchdog timeout.


so the watchdog appears to be completely useless.