So, I am interested in building a MMDVM (Multimode Digital Voice Modem) for hooking into DSTAR. So, I spent 8 hours working on a PI-Hat similar to the ZumSpot Pi Zero. Since ZumSpot seems to be dead, I decided to build my own. I finally have the schematic done, board placed and routed. Now, to get them built.
FWIW, I love the ST Micro STM32 MCUs. I use them in our professional work, through I am using a less powerful one on this design.
Here are photos of top and bottom: