VFD Display - Protocol inquiry

[StEeLz]

Hi EEV Community!

After seeing Dave hacking a VFD display on the episode #717, I've decided to salvage one as well (so beautiful/vintage).
I found that the Buick LeSabre instrument cluster had one, and the good part with this car is the VFD is a module, it is not directly attached to the mainboard. The 16 x 2 (5x7 pixels each) module has a driver integrated.
The 2 ICs on that module are Delco parts, undocumented of course. Seems like a driver and a memory/shift register.

I have now figured out all the pins, but I am struggling with the kind of protocol used. I would like to use an Arduino/Raspberry Pi to send messages on it.

3 Pins are active, I have done some screenshots.
Is it I2C? SPI? Serial? or proprietary?

This is the pattern repeated (31.8 Hz)


 
The sequences starts with 2 bits, then 32 bits :



When doing a closeup on the first 2 bits, it looks like this (Signal #1 : Zooming made some peaks disappear, but what is this middle signal, not square wave?). Clock seems to run around 500KHz:



If you ever saw that or have any clue...
I already appreciate if you read until here! Have a great day

Baptiste