EM75XX -- Restoring Modem AT Command Port (After Using Wrong Commands)

[JimHelms]

Using the incorrect AT Commands to change the composition of an EM7565/EM7511/MC7411 mode to QMI and/or MBIM is a common mistake which results in removing the modem's AT Command port.

Most generally this occurs when using the AT Commands on the EM7565/EM7511 that apply to the EM/MC74XX modems. The difference in the command as very minor (i.e., 1 digit).

For instance, to place a MC7455 modem in MBIM composition uses the AT Command:

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AT!USBCOMP=1,1,1009

where the EM75XX requires:

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AT!USBCOMP=1,3,1009

The modem can fixed while installed in or behind a router running OpenWRT/GoldenOrb/WiFiX firmware.

Using PuTTy, login the router using the routers IP address, generally 192.168.1.1

Once in, run the following command:

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echo 1199 9091 > /sys/bus/usb-serial/drivers/option1/new_id

Then repair the config with:

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picocom -b 115200 /dev/ttyUSB0

Then place the modem in MBIM composition with the follow commands:

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At!entercnd="A710"
At!usbcomp=1,3,1009
At!reset

And, that should do it.