Can I enter DFU from WDT ?

[Roger Clark]

Is it possible to enter DFU / OTA from a DWT

i.e if the code crashes, and I can't trigger DFU mode by writing to a characteristic, can the WDT jump straight to the DFU / OTA ?

[Nguyen Hoan Hoang]

DFU always get executed at reset so technically yes. The thing is dfu will check for valid App and jump right to it immediately so you'll end up in a jumping loop. You can have the DFU stay in DFU mode by holding a button when DFU is booting. If you don't have a button then you need to modify the DFU code to stay in DFU for a certain amount of seconds before booting the App. That would give a chance to reflash.

[Hung Bui]

Hi Roger,

You may need to write to flash before you let the WDT trigger a reset. The retained register GPREGRET is reset when WDT. If you have a look at the buttonless example in SDK v12, we write to flash before we trigger a reset, you can use that example and WDT to enter DFU bootloader. In SDK v13, we switch to GPREGRET instead.