I am using the EC25 quectel LTE module with Raspberry Pi 3 Model B. I can access the internet using serial pins of raspberry pi i.e. UART Tx and Rx. I can find ttyUSB[0-5] in ls \dev. I am sending AT commands to the module using these serial ports. But whenever I am resetting the 4G module using its reset pin, 4G modules restarts properly but ttyUSB* is not in the list of /dev. I have to power off and power on again the 4G module and then ports are again there in the list.

Am I doing something wrong? Please help me for following 2 issues:

  1. Is there any way to get the ports again while the device is powered up already?
  2. After every restart, Port numbers are changing. For ex, for the first time, I am getting ttyUSB0, ttyUSB1, ttyUSB2 and ttyUSB3. Sometimes, I get ttyUSB0, ttyUSB1, ttyUSB3 and ttyUSB4 and sometimes I even get ttyUSB0, ttyUSB1, ttyUSB4 and ttyUSB5. And I am using ttyUSB2 and ttyUSB3. How to resolve it?

Thanks in advance.

  • The following posts might help: "Need consistent physical USB port to have same USB number": lb.raspberrypi.org/forums/…. I have seen a couple of fixes, but sadly, none of which is simple.
    – tlfong01
    Commented Mar 11, 2020 at 7:49
  • 1
    Can you find some error messages in journalctl?
    – Ingo
    Commented Mar 11, 2020 at 9:01
  • 1
    I couldn't undertand the full result from journalctl but I found a line saying usb1-1-port2: Cannot enable. Maybe the USB cable is bad? But according to me, if this is the problem, then it should not run properly on power up. Commented Mar 11, 2020 at 11:38


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.