Serial Wire Debug Clock (SWDCLK) stuck at 2V!

[Yasir_Imran]

Hi,

We have a custom board with the nrf5340 SoC, after erasing it with the erase function included in the nrf extension for VScode, we started getting the following error:

NRF5340_xxAA_ENGDyasir@Em:~$ nrfjprog --deviceversion
ERROR: JLinkARM DLL reported an error. Try again. If error condition
ERROR: persists, run the same command again with argument --log, contact Nordic
ERROR: Semiconductor and provide the generated log.log file to them. 

By probing the SWDCLK and SWDIO pins from the JTAG on our custom board (with it connected to the nrf5340 DK), we found that the SWDCLK was stuck at 2V, whereas on a working board the SWDCLK was found to be at 3.3V. Attached is a screen shoot from the oscilloscope where the blue colored wave is the SWDCLK and the red is the SWDIO.

It might be worth noting that we have used the erase function from the nrf VScodes extention on this same device as well as other devices with the exact same hardware many times with no issues.

[Øyvind]

Hello, 

Can you please provide more details on how you are connecting the nRF5340DK to your custom board? Are both devices powered and ground at same level?

It might be worth noting that we have used the erase function from the nrf VScodes extention on this same device as well as other devices with the exact same hardware many times with no issues.

Does this mean that it worked before, but now it does not? Have you tried running nrfjprog --erase from the command line? 

Kind regards,
Øyvind

[Yasir_Imran]

Øyvind said:

Can you please provide more details on how you are connecting the nRF5340DK to your custom board? Are both devices powered and ground at same level?

The JTAG cable is connected to the board and it is powered by a battery, while the DK is normally connected to my PC. I have checked all the power supplies on the custom board, including the JTAG connector. All of them were at a normal voltage when compared to a working board, except for the SWDCLK which was at 2V as shown previously, so it is not a power supply issue. Additionally, I changed the SoC on that board and everything is now working properly. So, any idea what could have caused it? Again the last thing we did was that erase function!

I am probing the SDWCLK and SWDIO from the other side of the board while connecting it to the DK with a JTAG cable, if that is what you were asking for.

Øyvind said:

Does this mean that it worked before, but now it does not? Have you tried running nrfjprog --erase from the command line?

Yes it worked before, and yes I tried nrfjprog --eraseall; --recover from the command line, all with the same error.

Thanks!

Yasir

[Øyvind]

Are you able to provide schematics and pictures of your setup? Have you had a HW review of the custom board? What about ESD? The issue isn't clear to us, and we will need more information to get to the root cause.

Thanks!

Kind regards,
Øyvind

[Yasir_Imran]

Øyvind said:

Are you able to provide schematics and pictures of your setup? Have you had a HW review of the custom board? What about ESD? The issue isn't clear to us, and we will need more information to get to the root cause.

I am not sure if the diagram bellow is enough but that is all what I can provide at this point.

I am not worried about ESD, because I am sure I was grounded and we do have ESD mats. If it was ESD related, then it must have been caused by touching the DK, as the board only exposes the JTAG connector; which is very hard to touch unless it was done on purpose. However, all hardware related issues are on the table and have not been ruled out at all. The only reason that places these issues on the very unlikely side, is that we have more than 30 boards with the same hardware 12 of which have been under software development for at least 2 months now. The only board that encountered this issue, has been erased many times using the erase board in VScode. 

Kindest regards,

Yasir

[Øyvind]

Yasir, thanks for providing these details. I will need to discuss with our HW experts. The VS Code erase is the same as running nrfjprog --erase. 

Have you ensured that there is no battery drop when erasing the device? Or that the device was running on low battery during an erase?

[Øyvind]

What version of nrfjprog are you running? Please run command nrfjprog --version and provide the full output. Also, can you please provide the --log file as instructed in your initial case description

ERROR: JLinkARM DLL reported an error. Try again. If error condition
ERROR: persists, run the same command again with argument --log, contact Nordic
ERROR: Semiconductor and provide the generated log.log file to them. 

[Yasir_Imran]

Øyvind said:

Have you ensured that there is no battery drop when erasing the device? Or that the device was running on low battery during an erase?

That is in fact a strong possibility.