Often failed to connect to J-Link of nRF52840 DK

[RAlexeev]

Why does a laptop (MacBook Pro, 2019, macOS Catalina) lose connections with a nRF52840 DK so often? When I try to Build and Debug I often see such kind of errors:

Sometimes SES doesn't see a board and proposes to use a simulator, sometimes it starts to upload a firmware and after a while at some stage it propose to use the simulator, because the connection has failed. I tried to use various USB cables and ports, but the problem remains. Also I tried to flash using west flash command:

> west flash
-- west flash: rebuilding
ninja: no work to do.
-- west flash: using runner nrfjprog
Using board 683707495
-- runners.nrfjprog: Flashing file: /Users/PATH_TO_PROJECT/build/zephyr/zephyr.hex
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.
FATAL ERROR: command exited with status 33: nrfjprog --program /Users/PATH_TO_PROJECT/build/zephyr/zephyr.hex --sectoranduicrerase -f NRF52 --snr 683707495

And some logs after executing a command nrfjprog --program /Users/PATH_TO_PROJECT/build/zephyr/zephyr.hex --sectoranduicrerase -f NRF52 --snr 683969587 --log:

Fullscreen 4213.log_failed_1.log Download

[2021-Aug-11 23:11:56] [ info] --------------------------------------------------------------------------------
[2021-Aug-11 23:11:56] [ info] nrfjprog --program /Users/PATH_TO_PROJECT/build/zephyr/zephyr.hex --sectoranduicrerase -f NRF52 --snr 683969587 --log 
[2021-Aug-11 23:11:56] [ info] nrfjprog version 10.12.1 
[2021-Aug-11 23:11:56] [ info] --------------------------------------------------------------------------------
[2021-Aug-11 23:11:56] [debug] [ nRF0x0] - open_dll
[2021-Aug-11 23:11:56] [ info] [ nRF0x0] - Load library at /Applications/Nordic Semiconductor/nrfjprog/libjlinkarm_nrf52_nrfjprogdll.dylib.
[2021-Aug-11 23:11:56] [ info] [ nRF0x0] - Library loaded, loading member functions.
[2021-Aug-11 23:11:56] [ info] [ nRF0x0] - Member functions succesfully loaded.
[2021-Aug-11 23:11:56] [ info] [Backend] - Logger callback at 0x1095b1300 registered in Segger backend logger.
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] Logger callback at 0x1095b1300 registered in JLink logger.
[2021-Aug-11 23:11:56] [debug] [nRF520x0] - open
[2021-Aug-11 23:11:56] [debug] [Backend] - open_dll
[2021-Aug-11 23:11:56] [ info] [Backend] - No J-Link DLL path was provided. Attempting to auto detect.
[2021-Aug-11 23:11:56] [ info] [Backend] - Load library at /Applications/SEGGER/JLink/libjlinkarm.dylib.
[2021-Aug-11 23:11:56] [ info] [Backend] - Library loaded, loading member functions.
[2021-Aug-11 23:11:56] [ info] [Backend] - Member functions succesfully loaded.
[2021-Aug-11 23:11:56] [debug] [Backend] - dll_version
[2021-Aug-11 23:11:56] [ info] [Backend] - Segger dll version 6.88.a loaded.
[2021-Aug-11 23:11:56] [debug] [ nRF0x0] - enum_emu_snr
[2021-Aug-11 23:11:56] [debug] [nRF520x0] - enum_emu_snr
[2021-Aug-11 23:11:56] [debug] [Backend] - is_connected_to_emu
[2021-Aug-11 23:11:56] [debug] [Backend] - enum_emu_snr
[2021-Aug-11 23:11:56] [debug] [Backend] - ---just_enum_emu_snr
[2021-Aug-11 23:11:56] [debug] [Backend] - ---just_get_num_emus
[2021-Aug-11 23:11:56] [debug] [Backend] - is_connected_to_emu
[2021-Aug-11 23:11:56] [debug] [ nRF0x0] - connect_to_emu_with_snr
[2021-Aug-11 23:11:56] [debug] [nRF520x0] - connect_to_emu_with_snr
[2021-Aug-11 23:11:56] [debug] [Backend] - is_connected_to_emu
[2021-Aug-11 23:11:56] [debug] [Backend] - connect_to_emu_with_snr
[2021-Aug-11 23:11:56] [debug] [Backend] - is_connected_to_emu
[2021-Aug-11 23:11:56] [debug] [Backend] - ---just_enum_emu_snr
[2021-Aug-11 23:11:56] [debug] [Backend] - ---just_get_num_emus
[2021-Aug-11 23:11:56] [debug] [Backend] - ---just_connect_to_emu_with_snr
[2021-Aug-11 23:11:56] [debug] [Backend] - ---just_connect_to_emu_without_snr
[2021-Aug-11 23:11:56] [ info] [Backend] - Segger logging enabled.
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ]    ***** Error: 
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] Cannot connect to J-Link.
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] - 14.884ms returns "Cannot connect to J-Link."  
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] JLINK_HasError()  
[2021-Aug-11 23:11:56] [ info] [Backend] - JLinkARM.dll Open returned error 'Cannot connect to J-Link.'
[2021-Aug-11 23:11:56] [debug] [Backend] - is_connected_to_emu
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] JLINK_IsOpen()  
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] - 0.006ms returns 0x00  
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] JLINK_HasError()  
[2021-Aug-11 23:11:56] [debug] [ nRF0x0] - close_dll
[2021-Aug-11 23:11:56] [debug] [nRF520x0] - close
[2021-Aug-11 23:11:56] [debug] [Backend] - is_connected_to_emu
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] JLINK_IsOpen()  
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] - 0.006ms returns 0x00  
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] JLINK_HasError()  
[2021-Aug-11 23:11:56] [debug] [Backend] - close
[2021-Aug-11 23:11:56] [debug] [Backend] - disconnect_from_emu
[2021-Aug-11 23:11:56] [debug] [Backend] - is_connected_to_emu
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] JLINK_IsOpen()  
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] - 0.007ms returns 0x00  
[2021-Aug-11 23:11:56] [ info] [  JLink] - [Info    ] [JLink     ] JLINK_HasError()  
[2021-Aug-11 23:11:56] [debug] [Backend] - Segger Backend closed.
[2021-Aug-11 23:11:56] [debug] [nRF520x0] - nRF family DLL closed

And to flash a chip I need to physically unplug and plug boards from USB port several times until it works.

Also this it a log with a successful flashing, maybe it will be useful:

8345.log_success_1.log

7762.log_success_2.log

And I would like to mention that sometimes I see a foolish behaviour, when I have two boards connected to a laptop. I have one board connected (683707495) and I want to flash another board (683969587) from SES. Although I choose a correct USB Identification (SN) of the second board (683969587), but somehow the first board is flashed (683707495). And even when I try to flash again and I choose USB Identification (SN) of the first board (683707495), then the first board (683707495) is flashed. So there's no difference which USB Identification (SN) I choose. I already faced this problem many times today, while I was struggling with the original problem with losing connection with the board. Perhaps these two problems are related.

Sometimes after unplugging and plugging DK I have such messages:

Sometimes it couldn't be updated:

Sometimes the firmware is updated successfully:

And I don't change anything, I merely plug and unplug USB cables from boards.

I have the same problems with two boards, which I have right now, 683707495 and 683969587 are their USB Identifications (SN). It worth to mention that Nordic chips on the DK, it seems, work properly, according to LED blinking and Bluetooth connections. And problems are with J-Link debugger chips PCA10056 2.0.1 2020.43, which are located on the DKs.

What's wrong with DK, laptop or anything else? How is it possible to fix the problems with failed connections? Because now it's impossible to work with nRF52840 DKs.

[ovrebekk]

Hi 

Thanks for the detailed report. 

Have you tried another laptop to see if the issue is related to the laptop itself? 

Based on your testing it seems you have tried everything else, trying out different cables, boards etc. 

Best regards
Torbjørn

[RAlexeev]

Thanks for your response!

It's funny that today I didn't have such problem with boards, so there's sense to try another laptop, since I couldn't reproduce it. As soon as I notice the same problem I will try another laptop and without laptop charging that time. My colleague said that probably it's because of MacBook grounding issue, since in Russia MacBook charger adapter has only 2 pin plug (there's not a ground pin). And he recommended to try to ground the MacBook or try another PC with a proper grounding. I will add details and extra tests, when the problem occurs again.

It seems that a similar situation happened here, but for me not the first rebooting has helped: https://devzone.nordicsemi.com/f/nordic-q-a/41538/nrf52840-dk-j-link-not-working

Probably, this is a related case also: https://devzone.nordicsemi.com/f/nordic-q-a/20890/nus-disconnection-happens-when-i-touch-the-pcb. Since right before the describing issue above I noticed the same problem and I was struggling with it. I noticed that a connection between two boards was awful. And it was enough to cover one board by a hand to lose a connection.
And I tried to flash boards with other examples just for experimentation:
https://github.com/zephyrproject-rtos/zephyr/tree/zephyr-v2.6.0/samples/bluetooth/central (without bt_conn_disconnect() function)
https://github.com/zephyrproject-rtos/zephyr/tree/zephyr-v2.6.0/samples/bluetooth/peripheral
And they lost connections too often also. But now it seems everything is okay, although I didn't fix anything intentionally.

[ovrebekk]

Hi

Thanks for the update. 

Usually grounding issues like these are only a problem if you connect some other electrical device (such as an oscilloscope) to the same board. If the laptop and the oscilloscope has a different ground voltage you can get into problems. 

Regardless, just let me know if the issue occurs again, and provide some details regarding the situation in which the problem occurs. 

Best regards
Torbjørn