I have Lenovo X1 Carbon 6th (x1c6) but in my notebook configuration it was without LTE modem. And couple months it doesn't supported any LTE modems, but about 3 months ago it started to support two modems Mobile broadband Fibocom L850-GL and Mobile broadband Sierra EM7455.
I recently bought Mobile broadband Sierra EM7455 on aliexpress and tried to install it.
I bought just a modem, but it came with standard antennas.
But it was with a bunch of problems.
I always got an error that i have no SIM card in the tray.
So, I thought that I have a problems with SIM tray, espessially when i read this post
And I spent couple hours to attach some peace of plastic to my SIM tray
But i still got an error that SIM card is not inserted
Then I decided that I have software problems.
And that's how you can fix it if you have the same problems:
First of all we need to check if modem is connected
If everything is ok we should stop modemmanager
sudo systemctl stop ModemManager
After that we should download and unzip latest firmware from https://source.sierrawireless.com/resources/airprime/minicard/74xx/airprime-em_mc74xx-approved-fw-packages/
Also you could download another things there - https://source.sierrawireless.com/devices/em-series/em7455/
And update the firmware
sudo qmi-firmware-update -d 1199 -u *.cwe *.nvu
If you have an error on this stage (I had it too) you should see how to fix it at the bottom of this page.
Change the modem's USB composition to enable AT command ports:
sudo qmicli -d /dev/cdc-wdm1 --dms-swi-set-usb-composition=8
Power-cycle the modem as advised by qmicli:
sudo qmicli -d /dev/cdc-wdm1 --dms-swi-get-usb-composition
Verify that the three serial ports
/dev/ttyUSB2 are now available (assuming you do not have any other USB-serial converters plugged in):
# ls -l /dev/ttyUSB* crw-rw---- 1 root uucp 188, 0 Feb 14 20:11 /dev/ttyUSB0 crw-rw---- 1 root uucp 188, 1 Feb 14 20:11 /dev/ttyUSB1 crw-rw---- 1 root uucp 188, 2 Feb 14 20:11 /dev/ttyUSB2
After that we should connect to our modem via screen or picocom or tia
sudo screen /dev/ttyUSB2 115200
sudo picocom /dev/ttyUSB2 115200
And after that we should use AT commands
Enable command echo (if echo is initially disabled, you won't see this command as you type it):
Unlock engineering commands:
Check customization options (these are the author's options):
AT!CUSTOM? !CUSTOM: GPSENABLE 0x01 GPSSEL 0x01 IPV6ENABLE 0x01 SIMLPM 0x01 SINGLEAPNSWITCH 0x01 OK
Configure USB fast enumeration (swap
0 if you want to play it safe):
AT!CUSTOM? !CUSTOM: GPSENABLE 0x01 GPSSEL 0x01 IPV6ENABLE 0x01 SIMLPM 0x01 FASTENUMEN 0x02 SINGLEAPNSWITCH 0x01 OK
Configure the modem to ignore W_DISABLE:
AT!PCOFFEN? 2 OK
Reset the modem:
Problem with update firmware
I have nothing on the first step when i tried to flash new firmware.
But i found this guide
with this commands
AT!USBPRODUCT="Sierra Wireless EM7455 Qualcomm Snapdragon X7 LTE-A"
And only after that I successfully flashed new firmware.
sudo qmi-firmware-update --update -d 1199:9079 SWI9X30C_02.33.03.00.cwe SWI9X30C_02.33.03.00_GENERIC_002.072_000.nvu
sudo systemctl start ModemManager
And my modem is working now
Btw, you should create config file to connect to LTE
sudo vim /etc/qmi-network.conf
with this content (for MTS)
APN=internet.mts.ru APN_USER=mts APN_PASS=mts