Missing /dev/ttyUSB* nodes for SIM8200

I'm using OpenWRT in an x86_64 device (Beelink T4 Pro) with a SIMCOM SIM8200 5G + LTE modem. When I use Debian I'm able to issue AT commands over one of the extra /dev/ttyUSB* interfaces. Under OpenWRT the ttyUSB interfaces are missing.

lsusb -t:

/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/7p, 5000M
    |__ Port 3: Dev 2, If 0, Class=, Driver=, 5000M
    |__ Port 3: Dev 2, If 1, Class=, Driver=, 5000M
    |__ Port 3: Dev 2, If 2, Class=, Driver=, 5000M
    |__ Port 3: Dev 2, If 3, Class=, Driver=, 5000M
    |__ Port 3: Dev 2, If 4, Class=, Driver=, 5000M
    |__ Port 3: Dev 2, If 5, Class=, Driver=qmi_wwan, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/8p, 480M
    |__ Port 5: Dev 2, If 0, Class=, Driver=, 12M
    |__ Port 5: Dev 2, If 1, Class=, Driver=, 12M
    |__ Port 5: Dev 2, If 2, Class=, Driver=, 12M
    |__ Port 5: Dev 2, If 3, Class=, Driver=usbhid, 12M
    |__ Port 6: Dev 3, If 0, Class=, Driver=, 12M
    |__ Port 6: Dev 3, If 1, Class=, Driver=, 12M

A more detailed lsusb for the modem (vid:pid 1e0e:9001) is here.

Thanks for any help!

Appears to be a QMI modem, try the guide in https://openwrt.org/docs/guide-user/network/wan/wwan/start

It is already setup and routing traffic to my provider. I've had a Quectel RM500 modem in there before and the ttyUSB nodes showed up.

There's a separate kmod for the ttys. I think it's either kmod-usb-serial-qualcomm or kmod-usb-serial-sierrawireless.

It's kmod-usb-serial-option for this modem. SIMCom are re-using the same VID+PID for every(?) modem they make.... Pretty insane, but one advantage is that we don't have to add new IDs to the drivers

2 Likes

Thanks bmork, that did the trick!

My reason for wanting AT command access was to poke around the modem to find out why it halts every few hours. I literally have to either remove and replug the modem or reboot the system to get functionality back (this was happening under Debian as well). SIMCOM and Waveshare don't respond to requests for support which is unfortunate.

If you're using a USB adapter box, it may be a hardware issue of running out of DC power. LTE modems use a lot of power and also draw it in pulses that USB ports really weren't intended to supply.