Brick after sd_nvic_SystemReset() with enabled readback protection.

[Valer_I]

Hello,

My device is nRF51822 SD110 8.0.0.

The problem occured after firmware update in bootloader (own, not SDK) with readback protection enabled. So bootloader connects to host, receive the data and write it to firmware area of the flash. After all data transferred, central disconnect device. In bootloader disconnection handled in next way:

...
else if (evt_id == BLE_GAP_EVT_DISCONNECTED){ 
   sd_nvic_SystemReset();
}...

And device restarts, it jumps to botloader first and bootloader switches to firmware. Everithing works fine. But in case when readback protection enabled on chip, the last become brick after sd_nvic_SystemReset(); command. Power reset didn't help. What should I do to fix this?

[Hung Bui]

Hi Valer, When you mentioned "brick" you meant you can't recover (erase, reprogram) it or it just doesn't jump to application ? If it's the latter, you can test to debug, maybe using UART to check if it stuck somewhere in the bootloader ? Read back protection should only affect the SWD debugging interface. I don't think it would have anything to do with the bootloader.