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This blog is now hosted on a GPS/LTE modem (2021)

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No, really. Despite the timing of this article, this is not an April Fool's joke.

While developing software on the PinePhone, I came across this peculiar message in dmesg :

[ 25.476857] modem-power serial1-0: ADB KEY is '41618099' (you can use it to unlock ADB access to the modem)

For context, the PinePhone has a Quectel EG25-G modem, which handles GPS and wireless connectivity for the PinePhone. This piece of hardware is one of the few components on the phone which is closed-source.

When I saw that message and the mention of ADB, I immediately thought of Android Debug Bridge, the software commonly used to communicate with Android devices. "Surely," I thought, "it can't be talking about that ADB". Well, turns out it is.

The message links to an article which details the modem in question. It also links to an unlocker utility which, when used, prints out AT commands to enable adbd on the modem.

$ ./qadbkey-unlock 41618099 AT+QADBKEY="WUkkFzFSXLsuRM8t" AT+QCFG="usbcfg",0x2C7C,0x125,1,1,1,1,1,1,0

These can be sent to the modem using screen :

# screen /dev/ttyUSB2 115200

For whatever reason, my input wasn't being echoed back, but the screen session printed out "OK" twice, indicating it had executed the commands fine.

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