RM520N-GL serial console unresponsive over USB after firmware update

IoT Modules 5G Module
1

Hi,

I’m afraid I’ve soft-bricked my RM520N-GL, but I’m curious if there’s anything else I can try.

The modem was previously able to connect, but I was experiencing wildly oscillating connectivity, so I tried updating the firmware with qfirehose. (To be clear, I never used -e to clear nvram.)

After the update I could still reach the serial interface, but I kept getting stuck in CFUN = 5, and every time I tried to set CFUN to 1, I got +CME ERROR: 0
I tried downgrading, but I paid attention to the compatibility warnings and did not go back too far.

Out of frustration I changed the firmware a number of times because the problem kept persisting no matter what I tried, and after the last time I ended up unable to reach the serial interface over usb. The serial devices still show up connected to my linux laptop, but when I connect to /dev/ttyUSB2 my keystrokes are never echoed back to me.

Is there anything I can do to regain access and/or resolve things, or am I out of luck?

Thanks in advance for any help!

2

Hi @xyzzy

If I understand correctly, you are currently facing the following issues.
1- About the CFUN5 issue, could you wriing the FW verisons you flashed, please send AT+QGMR to query the detailed version information. I guess this may be because your module has a rollback function, and you flashed an old version.
2- About the unresponsive over USB, you need use the debug port to output the boot log, then we will know whether the modue is startup normally. And then try to find some clues to fix step by step.

Thanks