STM32F4 uses SPI for the MAX6966 LED driver
The STM32F4xx devices are not short of pins and they can be more flexibly used than on the STM32F1xx types. On a micromouse though, there is not a lot of physical space and I am not good at routing lots of traces around a board. Since I had already decided…

A wheelchair configuration micromouse has the wheels in the middle and skids at either end. Those skids cannot both be on the ground at the same time or, when the mouse encounters a step in the maze surface, the drive wheels will be lifted off the ground and the mouse may come to a halt. But, if there is too much clearance, the mouse will be able to rock back and forth quite a lot. It turns out that can have quite a big influence on behaviour…