Changing usbmode host back to auto

Hi all

I was copy pasting some AT Commands to a RM500U-CNV and I accidentally pasted at+qcfg=“usbmode”,host switching the module to host mode. I realized this after rebooting the device that the drivers for the Module won’t load and it looks like the device is being shown as xHCI controller when I cat /sys/kernel/debug/usb/devices.
Also I don’t have any serial ports in /dev/tty* (or at least they don’t work as on my device I had tty, ttyS0, ttyS1). Before could minicom using /dev/ttyUSB2

Question: is there a way to send an AT command to change the device back to “device” or “auto” mode?

If it can’t be done sending AT commands by using a hack/trick. Are there other possibilities like shorting certain pins on the module with a certain voltage or putting the module in a m.2 to usb case adapter?

Thank you in advance for any advice

Can someone at least please tell me which pins (the round ones) at the bottom of the module are for UART and what baud rate etc. is needed when using picocom / minicom?

Hi there,

Given the fact that ttyUSB* are not showing up, I would suggest to short USB_BOOT pin to VDD_EXT pin, after entering the emergency download mode(EDL), then flash the firmware and let’s give it a full restore.


Hi Louis

Thank you very much for your answer. I have the Quectel_RM500U-CN_Hardware_Design_V1.0.pdf in front of me. Looking at the Pin assignments, I don’t see USB_BOOT or VDD_EXT.

Could you please tell me where those are? How long do I need to short it? Just to clarify, by shorting you mean connect a wire bettween USB_BOOT and VDD_EXT? Or do I need to attach 2 wires to each pin, and apply a specific Voltage / Amperage to it?

It would be ideal if those pins are at the bottom of the module (the round pins)

Hi Louis

Wish you a happy new year!
Could you please shine some light on the issue I have regarding shorting USB_BOOT to VDD_EXT?
As written above the Hardware Design Manual doesn’t mention USB_BOOT & VDD_EXT.

Kind Regards