EM7455 Linux Issues

[dl5162]

@asaifou

Well, I did something very risky that bricks my Sierra Wireless EM7455. I was hoping that it will make it work on Windows and Debian, but It broke it.

I used those commands from this website forum.pfsense.org/index.php?topic=123828.0
I didn’t copy the whole code, just took this one:

AT!ENTERCND="A710"
AT!USBPID=9071,9070
AT!RESET

After rebooted my PC on windows, the card was unknown to the system, I reinstalled the Sierra Wireless Driver, but it still the same unknown driver. I booted over linux this time, but detects nothing.

There is no Modem COM port in windows nor TTY ports on Linux, in order to restore back the modem to factory,

I searched a way to revert back the PID of the card, on linux using usb_modeswitch, but I couldn’t do it, because I don’t know how to use it. Also I don’t know how to revert it back on windows.

Can you help me to revert back the PID of the card please

Sure, no problems. But please take it calm and easy and don’t do anything more hasty

Your modem had a Dell specific ID. This is made up of both a vendor ID (which belongs to Dell) and a product ID, which was assigned by Dell. The WIndows drivers know this exact combination. You changed half of that device ID, by changing the product ID. So you now have a bastard modem with a Dell vendor ID and Sierra Wireless product IDs. This combination is not recognized by neither Windows nor Linux.

But you can realitively easily work around that temporarily in Linux, allowing you to fix the issue by changing the USBPID back to the original. Do something like this (as root):

modprobe option
echo 413c 9071 > /sys/bus/usb-serial/drivers/option1/new_id

You should get a number of /dev/ttyUSBx devices. One of them will be the AT command serial port. Use it to change the PID back to your original (verify that I got the correct device IDs here!!!):

AT!ENTERCND="A710"
AT!USBPID=81B6,81B5
AT!RESET

This should get you back to where you were.

Then go ahead and make changes to the Linux drivers instead. Changing the modem is not the correct way forward. You are extremely lucky that Dell didn’t implement a BIOS whitelist like Lenovo does. If they had, then the laptop would have refused to boot. And you would have had to remove the modem from the laptop to fix it.