An ATTiny2313 microcontroller hidden away in a "hacked" GPO-746 Telephone paired up with an Android App that'll allow the GPO-746 to place and receive calls on a mobile network.

Test framework and experimental Android/Kotlin driver for the CH340G USB/Serial controller.

Docker container for the build environment and another to produce the schematics.

The schematics for the electronics can be found in ./schematic/schematic.html The Python code used to produce them is also to be found in this directory but the HTML has been pre-built if you don't want to hack on them.

Many of the requirements are hidden away in the Docker containers but there's still a couple of things needed on the outside.

Obviously

In theory at least, you can use some other system to build this on but there's a bunch of scripts in the top level ./bin/ directory that assume Linux.

For loading the microcontroller code on the chip

See the scripts and README.md in the ./bin/ directory.

Things you might want to "steal" to use in your own projects?

Android doesn't have drivers for serial/USB chips built in and there's a couple of more general Java based drivers available on GitHub. But here, I'm using a custom CH340G specific driver for a "special" use case - Using the handshaking lines for GPIO. There's also a Linux/libusb implementation that I'm using for testing.

The driver that's to be found in most systems uses the handshaking lines of the CH340G for the purpose for which they're intended or ignores them completely. But in here, we're using some of these lines as GPIO: R̅I̅ as an input and R̅T̅S̅ and D̅T̅R̅ as outputs.