Reverse-engineering project of the proprietary firmware and tools distributed with csdtk and GPRS_C_SDK for the Ai-Thinker A9/A9G and re-implement free alternatives.
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A9 free

What is the A9

The A9 is based on a system-on-a-chip namely RDA8955, made by RDA Technologies. It is a very powerful and versatile GSM/GPRS-capable microcontroller that was definitely conceived for mobile use, and probably used by various mobile phone manufacturers during the 2000's (personal opinion). A GPS-enabled version is also available, called A9G.

What is this project

The A9 currently depends on a set of proprietary tools and firmware blobs that have been left unmantained since 2018 by its manufacturer, Ai-Thinker. Therefore, this project aims to maintain the A9 and A9G by creating a free (as in freedom) version developed by the community. The A9 and A9G have great potential as IoT devices or even to build low-spec smartphones entirely based in free software.

What has been developed so far

Currently, no free firmware has been developed yet. The project is on a very initial phase where we need to know as much as possible about the system (e.g.: reverse-engineering) so we can start developing free software for it. doc/notes.txt contains a growing amount of information about what has been found so far and what still needs to be studied in further detail.

This is a list of ToDo things for this project:

  • De-compile firmware blobs using an automated tool e.g.: Ghidra.
  • Understand how the flashing process works.
  • Write minimal working example that runs on the hardware.
  • Write sample applications that interact with the hardware peripherals.
  • Port newlib and FreeRTOS to replace existing custom implementations.
  • Write a free bootloader that allows uploading application code.
  • Implement a free GSM/GPRS stack.
  • Implement a free GPS stack.

How to contribute

This is a very ambitious project that definitely takes a lot of time and resources. I am currently alone at this, and it is impossible to achieve all these targets without your support. So I encourage anyone interested in this project to join and help the project to become a reality. I think the A9 has a lot of potential that the community can benefit from.

So please review doc/notes.txt, give your feedback, provide new information and help development that allows us to use the A9 with free software only. Despite being based on closed-source binaries, the repositores provided by Ai-Thinker already include lots of documentation that will surely help us in knowing about the inner details on the A9 and the binaries themselves.