Just as a starting point, the AT&T RADIANT Core (ATTU304AA) phone seems to have a MediaTek MT6739.
According to
MediaTek's site, this chip is an ARM Cortex-A53.
The spec for Cortex-A53 can be found on the
ARM Developer siteAdditionally, the MediaTek site lists that the integrated graphics is the IMG PowerVR GE8100.
I can't find the spec for this online, but you could try clicking the contact link on
ImaginationTech's site and request the specification.
Otherwise, you could try to look at the
Android Kernel source branch for MediaTek to see if there's an implementation there.
These two things are probably the minimum required to actually be able to work on the OS.
However, to access peripherals, you would need to figure out which peripherals you need to access (such as the baseband like nullplan said) and implement drivers for them.
You could again try looking at the
Android Kernel source branch for MediaTek for implementations of how to do this.
You also may need to open up the phone to see which chips are actually on the PCB and then look them up.
Lastly, there's the problem of actually getting the OS on the phone. (In my experience) most of the time there's a separate chip that starts before the CPU that manages the bootloader, updating the ROM, etc.. Some phones allow bootloader unlocking, some don't. I don't know whether your phone does or not.
Just know that doing this will be a very long and hard task, there is a chance that you could brick your phone, and there's a good chance that the phone will break/die before you finish writing this if you do end up doing this.
Good luck!
nullplan wrote:
What I don't know is how the baseband firmware works. You will probably want to use a pre-approved blob from the manufacturer, since - let's face it - you probably don't want to learn how the SIM card and the radio interface work, and you probably won't be able to write these things in an FCC-compliant manner, let alone FCC-approved. But I don't know if that is stored on the baseband processor, or if you have to provide it, and if you can accidentally overwrite it, bricking the phone in the process (even the prettiest pictures don't make up for lack of wireless connectivity).
There's a good chance that you just send commands to the chip and it sends interrupts and data back. There likely isn't any messing with radio signals at the OS level, but I wouldn't know as I've never tried messing with the baseband before.