NRF52832 pins toggling during FW Flash

[Christopher]

I am working on a product which uses the nRF52832-CIAA. Whenever I update the firmware via JLINK/SWD, there is a pin (P0.19) which toggles during the FWUP process.

This signal only drives an NFET and has a pulldown on it, so it is not floating. I see it being actively driven from the MCU, and it is causing device failures during FW UP.

Here is an image of P0.19 during FW flashing via SWD.

Any advice? Is this expected?

Thanks!

[Simonr]

Hi

This seems very strange. What kind of firmware is on this device, and how does it fail during firmware updates? Can you provide an error code? Have you encountered this issue on multiple boards? If you are getting this error on one specific board, it might be a shorting somewhere on the board itself.

Best regards,

Simon

[Christopher]

Simon - 

It seems that this toggling is related to our code, but it is still very strange. Here is what we have observed.

1) Flash the device via JLink console (SWD) with a junk binary file, FW flash is successful

2) Erase the device via JLink console - successful erase, no toggling on the P0.19

1) Flash the device via SWD with our custom FW binary, FW flash is successful

2) Erase the device via JLink Console - successful erase, P0.19 toggles at a fixed rate until JLink session is terminated

What could cause this? How can this pin continue to toggle after the device has been erased?