RAK4630 WisBlock - COM Port Switch During Upload, Cannot Enter Bootloader (Arduino IDE 2.3.4)

WisBlock
1

I hope you’re well. I’m working with a WisBlock RAK4630 (base board 19003) using Arduino IDE 2.3.4. When I try to upload firmware, the device switches COM ports during flashing and fails to connect. I see errors like:
No trigger interface found for device with serial number
Waiting 500 ms for device to enter bootloader
Serial port could not be opened

I already:

changed cables (confirmed data cables)

deleted ghost COM ports in Device Manager

installed WinUSB drivers with Zadig

rebooted several times

but it still changes COM port during upload and then fails with Nordic DFU errors.

Right now the green and red LEDs blink slowly, but I cannot get the module to enter bootloader properly or accept new firmware.

Could you please advise if there is a simpler recovery method or if I must use a J-Link programmer to re-flash the bootloader?

I really appreciate your help because I’ve spent hours trying to recover it with no success.

Thanks a lot for any guidance you can share!

2

It is normal that the RAK4631 is switching COM ports during firmware upload.

My guess is that you are using the wrong Arduino BSP.

RAK4631 with Arduino bootloader is supported by the RAK-nRF52-Arduino BSP. Installation guide for this BSP can be found in How to Perform Installation of Board Support Package in Arduino IDE

RAK4631- R with RUI3 bootloader is supported by the RAK-nRF52-RUI BSP. Installation guide for this BSP can be found in RUI3 Supported IDE

How to know whether you have a RAK4631 with Arduino bootloader or with RUI3 bootloader?

Method 1
(1) Connect a terminal to the USB with 115200 baud 8N1
(2) Send the command AT+VER=?\r\n to the device
If it responds to this command in any way, it is a module with RUI3 bootloader.

Method 2
(1) Double push the reset button on the Base Board while connected over USB to a computer
If the device shows up as an external drive RAK4631, it has the Arduino Bootloader. If it just resets, it has the RUI3 Bootloader.

3

Thanks for your support. Unfortunately, despite following all the recommended steps and using the correct BSP and tools, I’m still facing persistent issues with the RAK4631 board.

The constant COM port switching during upload and the difficulty in getting a stable serial connection make the development process very frustrating and inefficient.

At this point, I can’t recommend this board for my projects due to these stability problems. I hope RAK can address these issues soon because the hardware potential is great but the current experience is disappointing.

Thanks again for your help.