Watchdog is activated in nRF51822 although NVIC_systemreset() is called but not in nRF51422

[Lennart Andersson]

In my nRF51822 I have an app & a dfu bootloader (modified from nRF51DK)   & softdevice.

The app starts the watchdog with 5 seconds timeout. An user can make the app to start the bootloader but if no dfu is made withing 90 seconds the bootloader exits and the nRF51822 goes back to normal operation. When the user starts the app writes a value to flash and starts the bootloader by calling the NVIC_systemreset() function. Then the nRF51822 exits "bootloader_mode" after 5 seconds although no DFU is made. if i check NRF_WDT->RUNSTATUS in the bootloaders sourcecode is says that the watchdog is running.

I have solved the problem by reloading the watchdog register in the bootloaders code if NRF_WDT->RUNSTATUS say's that the bootloader is running.

I have done the same dfu-bootloader in a nRF51422 but in that processor the watchdog is deactivated after a call to NVIC_systemreset()

Why does a call to NVIC_systemreset() deactivate the watchdog in nRF51422 but not in nRF51822?

Same softdevice in both. (s130_nrf51_2.0.0_softdevice.hex)

I have no panic with this since I have solved the problem, just curious.

  

[Vidar Berg]

WDT should keep running after soft reset (see section 12.1.19 of the nRF51 RM). Maybe it timed out before you read out the NRF_WDT->RUNSTATUS register, or that it didn't get started by the app?  51422 and 51822 are identical except that the former can be used with the ANT protocol stacks. 

[Lennart Andersson]

I have found the reason, shame on me. I have a a much longer WD timeout in the nRF51422 code than in the nRF51822 code.