For my OnStep telescope mount controller (visit my [group][1] for more information.)

This design is built around the Teensy4.1 processor (available on Amazon, PJRC, etc.) It has 8MB of flash, runs at 600MHz, and has a fast double precision capable floating point unit.  The T4.1 is the fastest/most capable OnStep supported MCU. This has a moderate amount of soldering necessary but most components needed to build one of these can be obtained from EasyEDA/LCSC and eBay.

**Note: This design is for non-commercial use only (see License terms, CC-BY-NC-SA 3.0)**

This controller includes the following features:

* Power: Coaxial power jack, fuse, and power switch connection.
* Stepper drivers: Four, one for RA/Azm, one for Dec/Alt, one for a focuser, and one for a rotator/second focuser. It's designed to support full control (microstep mode etc.) of older StepStick drivers as well as TMC SPI ones, in all four sockets. All stepper motor connections are available on RJ jacks at the PCB back (screw terminals are optional.)
* WiFi or Ethernet: WeMos D1 Mini ESP8266 foot-print (uses Serial2.)
* Micro USB port built into the Teensy4.1.
* Status LED.
* Mini speaker for alert buzzer.
* DB15 15 pin D-Sub connector: primary external I/O for Gnd, +3.3V, 5V, two Home Switches, PEC, PPS, I2C, the Serial1 port, and two channels of A/B encoder inputs.
* 3.5mm stereo mini jack: secondary external I/O for Limit Switches and Reticle.
* RJ12 Modular connector: ST4 guider interface (with optional 5V power.)

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Changes relative to MaxPCB3.6:

General use of SMT components to keep soldering to a minimum as EasyEDA now makes this easy to order/low cost.

Design allows use of readily available TMC2209 drivers, they have the best performance/cost.

Removed DS3231 RTC module in favor of using a battery and Teensy4.1 built-in RTC.  This makes room for plugging USB into the WeMos D1 Mini while operating and/or using the ESP32 based WeMos D1 Mini boards.

The following pins have changed…

* PIN34 M0_1 was changed to MISO (Teensy RX8, forms a bus for TMC2209 RX/PDN-UART pins.)
* PIN35 M1_1 was changed to M2_1 (Teensy TX8, FYSETC v3.1 TMC2209 TX pin.)
* PIN36 M2_1 was changed to M1_1 (swapped for above.)
* PIN37 MISO was changed to M0_1 (swapped for above.)

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History
- Version4.0 - First release

- Version4.01 - Changed encoder pullup from 5V to 3.3V

  [1]: https://groups.io/g/onstep