November Update:
As time permits, I am still working on trying to get the GTR gauges on the factory NAV screen.
There is a little known "Test Port" on the AV modules. This allows console/terminal/root access.
For this to work, there are a few different things the hardware must do.
To make it easy (almost plug and play) I have developed this:
(The grainy pic is due to the low resolution 3D render, no need to spend extra on a high quality image!)
What does this board do?
• Adds pull up resistor to IT-PC
• Converts the PC-IT 3.3v logic level to 12+ and inverts the signal
• Allows any Mac/PC/Linux serial program (Putty, serial terminal, etc) to connect to the AV unit's serial console, and execute on board commands... and there are a lot of them!
I am currently building the prototype on a perfboard to test/scope voltage levels and waveforms.
If all goes well, I hope to have console access later today.