nrf51422 bricked (N5 Starter Kit from Dynastream)

[Jens Meder]

Hi guys,

we are currently evaluating the nrf51422 chips for our product. We have ordered the N5 Starter Kit from Dynastream and were able to flash different sample projects and custom code via Keil µVision. We have flashed the chips with the S310 softdevice as we need both BLE and ANT support. Sometimes Keil refused to flash our application (No Cortex M0 device found) so we had to fire up nrfgo studio and reflash the S310 softdevice. Unfortunately, we have been unable flash anything at all (neither softdevice nor application) nor erase the chips since yesterday. nrfgo studio recognizes our Segger J-Link but is unable to recognize the nrf51422s so we cannot recover the chips. The same goes for J-Link commander. It recognizes the Segger but no devices. It only detects the VTarget voltage with either 1.7V when using a CR2032 coin cell or 3.5V when powered via USB. We tried to recover via nrfjprog from the command line but it says it cannot detect any NRF51 devices.Running the command sequence to erase the flash via J-Link (r, w4 4001e504 2, ...) doesn't work either.

Have we bricked our chips or is there any other way to revive our devices?

Thanks in advance!

[Jens Meder]

Hi Asbjørn,

thanks for you reply. After a lot of trial and error we have found the issue: it was indeed the VDD. Unfortunately, it has been obfuscated by some non obvious characteristics of the Dynastream Devkit. In case someone runs into the same issues, here is the solution:

The voltage of the 3.6V coin cell has dropped below 1.7V due to discharge that made it impossible to flash new code to the nrf51422 chips. When we mounted the chips to the usb dev board the voltage was at around 3.5V as measured via J-Link. What we didn't now: The usb dev board that comes with the N5 starter kit blocks the J-Link interface. The chip is fully operational but you simply cannot flash any code on it while mounted on the usb board.

Bottom line is that you can only flash the chips while mounted on the battery board. So you either have to solder some headers to the battery board and use an external power source or buy some rechargeable coin cells.

[Asbjørn]

I'm glad you figured it out and we really appreciate that you took the time to update this case with the additional information and the solution. Thank you for helping the forum.