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]

We are seeing the pin toggle on all boards while we are flashing FW via JTAG/SWD. The flashing succeeds, no problem there, but the toggling of the pin causing a function failure on the board (this pin should not be toggling during fw flashing)

We have encountered this on all of our boards.

[Simonr]

Hi

Most likely there is something in your code making the P0.19 pin toggle like this. You should take a closer look at your code as there likely is something there causing this problem.

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? 

[Simonr]

Hi

The pin likely keeps toggling because the erase won't "take effect" until you reset the chip. If you try to erase the device, and then resetting it before terminating the JLINK session, you should see the P0.19 stop toggling. As to what exactly causes it to toggle, the firmware you are using were most likely at one point telling the P0.19 to toggle. You will just have to go through your code to find out what exactly is causing it. 

Best regards,

Simon