Restoring the Modem COM Port for Sierra Wireless MC7750

How to tutorials for modems, hotspots, dongles
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Restoring the Modem COM Port for Sierra Wireless MC7750

Post by JimHelms » Sun Oct 21, 2018 9:28 pm

This tutorial will demonstrate a fairly easy way to restore the Sierra Wireless modem COM port using a Windows machine. While I will be working with the Sierra Wireless MC7750 modem, the same procedure worked for the MC7700 and will most likely work for other Sierra Wireless modems.

As with all the tutorials, use at your own risk.

You will first need to download and install the latest Sierra Wireless drivers for Windows. This is allow Windows to communicate with the modem.

I came across a Sierra Wireless MC7750 that lost its modem COM port. The only port available was the DM COM port. In later modem modems this stage may be referred to as QLoader mode.

This is what we see when using the Huawei Terminal:

DM COM Port.png
DM COM Port.png (40.56 KiB) Viewed 1090 times

When you download the MC7750 firmware from Sierra Wireless, the download contains two files: the modem firmware .cwe file, and the FlashTool.

Needless to say, the flash tool when used, offers little help since it cannot properly detect the modem:

FlashTool 1.png
FlashTool 1.png (92.3 KiB) Viewed 1090 times

FlashTool 2.png
FlashTool 2.png (306.16 KiB) Viewed 1090 times

We will unzip/extract the MC7750 firmware flashtool. Right click the exe firmware and extract its contents.
Extract MC7750 Firmware.png

Create a new folder and place the MC7750 firmware .cwe, the fdt2.exe, the combo_script.txt and the GobiApi.dll files into the new folder. Next, execute the fdt2.exe application by double clicking the file:

Execute FDT2 Application.png
Execute FDT2 Application.png (80.29 KiB) Viewed 1090 times

And, give it a few minutes to do its job.

DFT2 Firmware Uploaded.png
DFT2 Firmware Uploaded.png (106.69 KiB) Viewed 1090 times

After the firmware is updated, press the ENTER and the modem will go off line. Be patient and wait a minute or two, then unplug the power to the modem.

Wait a few seconds and plug the power back to the modem.

When the modem reboots “completely” (give it a couple of minutes if necessary for the drivers to load), you can check to see if the modem COM port is now available.

You can test the Modem COM port by entering the ATI command. If it will not accept the command, reboot the modem and reflash it again using the steps above.

Next, just to assure the firmware did flash correctly, we will reflash the firmware using the MC7700 OEM firmware kit. This may or may not be required, but I generally err on the side of caution. And it sure easier to do it now than have to redo it later.

Reflash using the OEM firmware.png

Again, while you are there, test out the modem port with the ATI command:

Test the OEM firmware flash.png
Test the OEM firmware flash.png (68.21 KiB) Viewed 1087 times


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