Not able to flash custom board with nordic nrf52840 DK unless the reset pin tied to NRF_VDD

[Kalrz]

Hallo,

IDE: Segger Embedded Studio

nrf52840 DK

Custom Board with ProteusIII

I have designed a custom board with ProteusIII (nrf52840 SoC) and was working with the board for the past 1 month. Recently in the middle of nowhere, the custom board cannot be flashed using the nrf52840DK anymore unless the reset pin from the custom board is held high using a jumper. 

Please find the error log below:

Connecting ‘J-Link’ using ‘USB’
Connecting to target using SWD
Loaded C:/Program Files/SEGGER/SEGGER Embedded Studio for ARM 5.10a/bin/JLink_x64.dll
Firmware Version: J-Link OB-SAM3U128-V2-NordicSemi compiled Mar 17 2020 14:43:00
DLL Version: 6.80a
Hardware Version: V1.00
Target Voltage: 3.300
Device "NRF52840_XXAA" selected.
InitTarget() start
InitTarget() end
InitTarget() start
InitTarget() end
connect failed
Failed to connect to target.
No idcode detected.
Please check connection and Target Interface Type

I am able to flash other boards using nrf52840 DK (Evaluation board from ProteusIII). I had programmed many times without the use of reset pin. Now each time, I need to provide high voltage to reset pin in order to flash the chip properly.

How do I resolve this issue? Is there anyway to reset the chip to its previous configurations? 

Thank you

[Håkon Alseth]

Hi,

 

Kalrz said:

I have to mentioned this behavior started all of a sudden. I was flashing the custom board from morning and now it is no more possible without the reset pin been held high externally. 

This is very interesting.

Do all custom boards behave similarly, or is it only one board that misbehaves?

What is the voltage level of the nRESET pin on the faulty board? meaning; is there any reason why it should have to be forced to VDD?

 

Kind regards,

Håkon

[Kalrz]

Hallo,

Håkon Alseth said:

Do all custom boards behave similarly, or is it only one board that misbehaves?

It is just one board that misbehaves.

Håkon Alseth said:

What is the voltage level of the nRESET pin on the faulty board? meaning; is there any reason why it should have to be forced to VDD?

I did not measure the voltage level of the RESET pin. I should have done that first. But pretty sure it was not VDD. May be way too less to be recognized as an high level. (But again, I did not measure it and I feel so bad since I didn't). 

Again today morning after 3 days i power up the board and successfully flashed firmware using DK. Strange. Reset pin reads a voltage of VDD without forcing it to be (externally). 

Now the problem is resolved but is quite disappointed that I was not able to find the root course. I think it might happen in the future as well. Might be quit a good idea to connect reset pin to VDD with a 0 ohm resistor in the final design of my board.

What do you think?

best regards,

Karlz

[Håkon Alseth]

Hi Karlz,

 

Kalrz said:

I did not measure the voltage level of the RESET pin. I should have done that first. But pretty sure it was not VDD. May be way too less to be recognized as an high level. (But again, I did not measure it and I feel so bad since I didn't). 

Don't worry too much. If it happens again, it would be interesting to see what the voltage is on the reset pin.

 

Kalrz said:

Again today morning after 3 days i power up the board and successfully flashed firmware using DK. Strange. Reset pin reads a voltage of VDD without forcing it to be (externally). 

Since this only occurred on one board, it might be a small speck of solder-tin that caused problems for all we know.

If this exact issue happens on several boards; the problem might link to design-wise problems.

 

Kalrz said:

Now the problem is resolved but is quite disappointed that I was not able to find the root course. I think it might happen in the future as well. Might be quit a good idea to connect reset pin to VDD with a 0 ohm resistor in the final design of my board.

 What I would recommend is to check on several of your boards, and see if this issue appears on more than one board. If that is the case, more in-depth investigation is needed. nRESET pin has internal pull up, so in normal use-cases; there's no need to add a hard connection between VDD and nRESET.

 

Kind regards,

Håkon

[Kalrz]

Hi Hakon,

Thanks for your help and guidlines. I hope I could figure out the root course if in case if it happens again. I will be updating here. 

Thanks for your time and have a nice day.

[Håkon Alseth]

Hi Karlz,

 

Feel free to update the case if you see this issue again.

Kalrz said:

Thanks for your time and have a nice day.

Thank you very much, and likewise!

Kind regards,

Håkon