So a while back... actually in August 2021... wow ok... I designed a PCB using Fritzing to replicate the signals the system would receive from the Hilux when all connected. So, steering wheel controls, battery positive, key (acc, ign), transmission in reverse and automatic dash light dimming (sunlight sensor). The PCB was produced using their service with Aisler and came out really nice:

To determine the circuit and resistors required, I used the Toyota wiring diagram and diagnostic process table to get reasonably close. I wasn't too stressed about precision because I'm going to build in the ability to tune the values once in the vehicle.

Using an amazing tool from Paul Falstad I was able to simulate the circuit to play with different resistor values in order to get reasonably close.

Last weekend I was able to dedicate some time... (Quick side note, no progress has been made on this project for a while due to work commitments, but they are now resolved) into finally soldering the components to the board to see if it actually worked...

And god damn, it did work! Perfectly actually... Using a Milwaukee M12 battery as a power source, I was able to replicate near perfect "expected" results from the board, which means we're on the right track

So now in combination with the amazing Rasbperry Pi Pico I can now start interpreting the steering wheel controls, which will then be piped to the main controller through serial for action by the main software.

Progress, we're moving along. I'll post an update about moving away from Flutter and on to Web Components for the main app at a later date.