For my OnStep telescope mount controller (visit my [group][1] for more information.) This design is built around the ESP32S. There are four stepper drivers (one for RA/Azm, one for Dec/Alt, one for a focuser, and one for a rotator/second focuser.) RA/Azm and Dec/Alt share a common SPI bus best used with SSS TMC2130 and TMC5160 stepper drivers only though others can work with some limitations. The focuser/rotator stepper drivers can be of any "step-stick" design but usually TMC2208's will be the best choice. All stepper motor connections are available on RJ jacks at the PCB back (or optionally screw-terminals.) There's a power jack, fuse, and power switch connection. There are several connectivity options: USB, an I2C port (w/footprint for the DS3231 RTC.) There are two serial ports. Serial0 is brought out on a pin-header connector (w/power) but using it disables the ESP32S micro-usb port; fortunately the ESP32S has on-board Bluetooth so this isn't much of a limitation. Serial1 is on a WeMos D1 Mini (ESP8266) foot-print for Wifi support. In this design it is possible to flash the WeMos through OnStep. There is a D-Sub connector DB9 that has home SW inputs (or I2C depending on configuration,) PEC input, and two channels of A/B encoder inputs (which run to the ESP8266.) There's also a modular connector for an ST4 guider interface (with optional 5V power.) On a 3.5mm stereo mini jack is a limit sense input (to stop the mount) and also a reticule LED output available if Aux8 is not used for other purposes like the on-board mini speaker as an alert buzzer.) [1]: https://groups.io/g/onstep History * Version 3.0 Initial Release * Version 3.02 Switched EN pull-down resistor from 4.7K to 470 Ohms * Version 3.021 Silkscreen improvements, removed unused pads on RTC * Version 3.03 Added 3 position jumper under WeMos for Aux8 connection to speaker or Mini Jack (this allows a socket jumper lead to connect Aux2 to the Mini Jack if the user wants to use Aux2 for OneWire etc.) * Version 3.04 Added ground to ENable pin of Axis3 driver and 4.7K pull-down resistor to ENable pin of Axis4 driver. These ensure a wider variety of drivers are properly enabled. Added 4.7K pull-up to the ESP8266 GPIO0 pin (also serves as the Axis2 Dir pin.) This ensures GPIO0 is logic high for proper boot up even if some driver in Axis2 happens to have a weak pull-down on its Dir pin (probably not needed.)