NRF52840 RESET Pin stuck at LOW

[tejaChintalapati]

Hi,

I have a custom nRF52840 board. I mistakenly tried flashing the custom nRF52840 board with STM32 firmware. From that moment on, I can't flash board. When connected to J-Link, LED on J-Link is solid RED. I noticed that the RESET pin is in LOW level.

Here's what I tried after going through questions in forum:

1. Pulled up the RESET pin to 3.3V.
2. Erased the chip from SES
3. Recovered the board using nRFGoStudio and it was successful.
4. Followed one post which suggested to use J-Link commander to reset and write values after resetting. Everything went successful.
5. In system_nRF52840.c, I commented this section, as recommended by one of the other posts.

   #if defined (CONFIG_GPIO_AS_PINRESET)
           if (((NRF_UICR->PSELRESET[0] & UICR_PSELRESET_CONNECT_Msk) != (UICR_PSELRESET_CONNECT_Connected << UICR_PSELRESET_CONNECT_Pos)) ||
               ((NRF_UICR->PSELRESET[1] & UICR_PSELRESET_CONNECT_Msk) != (UICR_PSELRESET_CONNECT_Connected << UICR_PSELRESET_CONNECT_Pos))){
               NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos;
               while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
               NRF_UICR->PSELRESET[0] = 18;
               while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
               NRF_UICR->PSELRESET[1] = 18;
               while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
               NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos;
               while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}
               NVIC_SystemReset();
           }
       #endif

However, the RESET pin still needs to be pulled-up to HIGH for the board to responsd to J-Link.

Can you please help me un-brick this board?

[Kenneth]

Which pins have you connected between your board and J-link? It should be sufficient to connect gnd, vdd, swdclk and swdio.

Also, if you open a command line window you can call 'nrfjprog --readuicr dump_uicr.hex' when failling, I just want to check if UICR still have pin reset enabled after all your changes.

To completely erase a board you can call 'nrfjprog --recover' or 'nrfjprog --eraseall'.

Best regards,
Kenneth

[tejaChintalapati]

Hi Kenneth,

Thanks for responding. Here are my responses:

1. I have a standard 10 pin SWD connector.
2. I can't set the correct "Family" to run nrfjprog --readuicr dump_uicr.hex. The default is set to NRF51 in nrfjprog.ini and I can't seem to modify it - I am getting some Windows Error saying I don't have enough privileges. Can you please tell me how to set the family while running this command?
3. I can't run nrfprog --eraseall either because of incorrect family setting.

Can you please tell me how to change the family using the commands?

[tejaChintalapati]

I did try running "nrfjprog --family nRF52 --eraseall". But, I am getting this error:

"ERROR: The --family option given with the command (or the default from nrfjprog.ini)
ERROR: does not match the device connected."

[Kenneth]

What does it say if you type "nrfjprog --version"? Can it be that you have more than 1 jlink programmer and/or nRF board (DK/dongle etc) connected to your PC?

Kenneth

[tejaChintalapati]

Hi Kenneth,

• Here's the version:

nrfjprog version: 8.5.0
JLinkARM.dll version: 6.44g.

• I only have 1 programmer connected to PC.

[Kenneth]

That is an old version, the latest is 10.6.0. Try it from here:
https://www.nordicsemi.com/Software-and-tools/Development-Tools/nRF-Command-Line-Tools/Download

[tejaChintalapati]

This helped me fix the issue. I unbricked the board and everything is working the way it should.

Thanks, Kenneth for all the help.