Could not fetch memory size of target devkit: Error: Error occured when get library info. Errorcode: CouldNotOpenDevice (0x4) Lowlevel error: JLINKARM_DLL_ERROR (ffffff9a)

[harry4951]

Hi, I cant get access to my custom nrf52840 board after I click "Erase all" in "Programmer" in "nRF Connect for Desktop". This custom board has been working with me for at least 3 months with the same connection, but suddenly after I clicked "Erase all" last Thursday, I felt that it didnt fully erase the chip but after two seconds it popped up with error mentioned in the title and I cant access it anymore. I searched all the related issues in the forum but none helps. I can get access to the nrf52DK board if I disconnect all the connections with the custom nrf52840 board which means the jlinkob in the nrf52DK is good. Please help to figure it out. Thanks.

Basic info: 

System: Windows 10 Pro

nRF Connect for Desktop v3.7.0 Windows 64bit -> Programmer v1.4.11

nrfjprog version: 10.13.0

JLinkARM.dll version: 7.50a

Setup:

Issues:

I tried nrfjprog --recover and nrfjprog --reset but in both cases got 

ERROR: [SeggerBackend] - JLinkARM.dll reported "-1", "An unknown error.".

I tried Jlink commander also:

Best

/CJ

[harry4951]

Hi Simon,

There must be something wrong with this "Erase All" command. The only second custom board I have just got the same problem after this command but this time instead of in the nRF Connect for Desktop, it was in the Segger studio.

I have updated the J-Link to v7.52a. I supplied the board with 3.3V, the board still worked one second ago before this "Erase All" command!

I tried nrfjprog --eraseall --log, but all I got were these:

Please help! This is so frustrating! I dont have any board to work with now, but the deadline is approaching!

Thanks

/CJ

PS: And if I disconnect all the connections between my custom nrf52840 board and nrf52DK board, the nrf52DK board can work properly standalone.