For my OnStep telescope mount controller (visit my group for more information.) This design is built around the ESP32S.

Features:

• Three stepper drivers (one for RA/Azm, one for Dec/Alt, and one for a focuser or rotator.)
• Power jack, fuse, and power switch connection.
• DB9 (d-sub miniature) jack for quick connection of optional optical encoders, home position switches, and the PEC sensor.
• Limit Sense input to stop the mount (panic button, switches on the mount, etc.)

Connectivity options:

• USB
• Bluetooth (onboard the ESP32.)
• Wifi support via the WeMos D1 Mini (ESP8266) which can plug directly into the PCB (using 0.1" socket headers.) Encoders are supported through the WeMos D1 Mini and brought out on the DB9 connector.
• I2C support so the DS3231 (RTC) can plug directly in the PCB. The BME280 (weather sensors) can potentially be attached outside on the DB9 connector depending on settings.
• ST4 port auto-guider interface (with optional 5V power.)

Revisions: 2.0 Initial Release 2.1 Disconnected SLP/RST on Axis1/2 so ESP32 GPIO12 is not held HIGH during boot 2.2 Added +5V to USB connector going to ESP32 (otherwise USB on some of these doesn't work.) Added S310FA Diode to protect TMC2xxx stepper drivers due to above requirement.