For my OnStep telescope mount controller (visit my group for more information.) This design is built around the Teensy3.2 and supports the most important features while keeping a small size. There are two stepper drivers (one for RA/Azm and one for Dec/Alt.) There's a power jack, fuse, and power switch connection. Additionally, there's a limit sense input (to stop the mount,) and a PEC sensor input. For connectivity there's a USB Port and support for Wifi using a WeMos D1 Mini Pro. There's also a modular connector for an ST4 guider interface (with optional 5V power.) This model is designed to fit an inexpensive aluminum case (eBay item) and offers easy connections via RJ jacks for the stepper motors and ST4 port and 3.5mm stereo jacks for other connections.