After quite a bit of work, our 266 interfaces are now fully defined. From there, we managed to define pin assignments for the 4 × 48 GPIO pins offered by the 4 Parallella boards. We now have 192 pins assigned and 100 pins left, plenty enough for future extensions.
This work was quite useful to identify some missing components in our design, especially with respect to the driving of various controls and indicators. We also managed to remove quite a few cables, or use shorter ones, which should simplify our internal wiring.