Chip shortage. Any more explanation needed? When I started, the STM32F407 was cheap, fast and had plenty of IO pins and therefore, an ideal choice I thought :)

Now you have to pay 40 bucks for the dev board I used and as I'm trying to make a dev kit out of this project I need some more accessible components.

The RP Pico (with an RP2040) comes at a price of 4 Euro, so I ordered a few boards to get started.

Next, I removed my old mainboard:

Goodbye and thank you for your service!

Here comes the new generation (and there are significantly less IO pins, actually, I need them all and some more):

Right, so I had to hard-wire the enable pin of the displays power supply to +3V3, there was just no pin left.

And it took some time with the logic analyzer to figure out the little differences in the SPI setup to finally get something showing up:

Exactly one key gave me something and that something was also distorted. But after getting the timing, reset, d/c etc. signals and default low/hight states right, ALL displays were willing to work!

Another step forward and in parallel I started with my efforts in designing a more complete keyboard PCB.... still based on my Atoms.