Failed to Find /dev/ttyUSBx from Sierra EM7455

On Linux, you will need /dev/ttyUSB2 to communicate with EM7455 with AT commands and load EM7455 driver right.

For example, you might got the following result after entering sudo mmcli -m 0 if you have installed the same EM7455 module on Windows before and firmware.

  System   |            device: /sys/devices/platform/3610000.xhci/usb2/2-1/2-1.2
           |           drivers: cdc_mbim
           |            plugin: sierra
           |      primary port: cdc-wdm0
           |             ports: cdc-wdm0 (mbim), wwan0 (net)

Solution

  • Find a x86 computer with Windows installed

  • Put the EM7455 on x86 computer

  • Install Windows EM7455 driver [linkarrow-up-right]

  • Installed the below tools and make the COM ports of EM7455 could be found on device manager

file-archive
3MB
  • Put the EM7455 back to NRU series and the driver will be loaded properly

Cause

Some hard-wired configurations on EM7455 will be changed after Windows driver installed.

Reference

https://forum.sierrawireless.com/t/no-serial-ports-for-mc7304-after-fw-upgrade/9701arrow-up-right

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