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e303c-voice

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Some notes on E303 voice capability

FIXME this article is very WIP-y because I never finished this project, you've been warned

Huawei dongles are pretty ubiquitous. One of our local operators (Vivo) used it a lot, in a myriad of different models. Mine, particularly, is a E303C, which happens to have voice support. Hence, it's possible to place and receive calls using such dongles. Under normal circunstancers, one would use the Windows app., which provides an integrated caller. You'll soon notice that there's absolutely no related multimedia devices on devmgmt.msc. It does that using only standard serial ports.

The basic theory

When you plug the thing to the computer, three ttyUSB things pop into your /dev. Two of them should accept AT commands, one don't. This strange port is actually where the PCM data flows through during calls. Theoretically, you should be able to place calls per via AT commands and then pipe data from this serial port into something like aplay, which should send the data to your DAC device, whatever it is. Better yet if you understand droid speak, because you won't need ALSA.

As you may imagine, there are several gotchas getting there from here, though. You'll likely run into issues regarding USB mode switching or you won't be able to find the correct PCM format to decode the voice data. Also, there are some specific AT commands you should issue, under some circunstances. This manual should help you with that.

Another common issue is the locked voice function. Mine came with unlocked (then I locked it when messing with different firmwares…) Unlocking it is a nightmare, the only way I could find was to pay some indians (I do not remember the actual name) to be able to unlock it.

e303c-voice.1589513803.txt.gz · Last modified: 2020/05/15 03:36 by prppedro