Servomotor3

Gearotons M17 — an open-source servomotor you can talk to

The M17 is a NEMA-17 integrated servomotor: motor, closed-loop driver, motion controller and magnetic encoder in one unit. It daisy-chains over RS-485, ships with Python and Arduino libraries, and has a first-party MCP server so an AI assistant (Claude Desktop, Claude Code, Cursor, …) can drive real motors from plain English.

Hardware, firmware and software are all in this repository under the MIT license.

All sizes: 12–24 V, up to ~1.1 A, up to 560 RPM, closed-loop 32 kHz control, RS-485 at 230400 baud, 64-bit unique ID + one-byte alias per motor, standard NEMA-17 mount. Indoor use (IP20).

Buy one: gearotons.com (from $20; ships worldwide from Shenzhen). Documentation: 9o.at/M17_1.5 · Datasheet (PDF) · Python API · Arduino API

Quick start (Python)

pip install servomotor

import time, servomotor

servomotor.open_serial_port()                      # prompts for the USB–RS-485 adapter the first time
m = servomotor.M3("X", time_unit="seconds", position_unit="shaft_rotations")
m.enable_mosfets()
m.trapezoid_move(1.0, 1.0)                         # one full turn, in one second
time.sleep(1.1)
m.disable_mosfets()
servomotor.close_serial_port()

That is python_programs/example_trapezoid_move.py. Units are yours to choose (degrees, rotations, radians, encoder counts; seconds or milliseconds) — the library converts. No STEP/DIR timing, no microstep configuration.

Quick start (Arduino / ESP32)

Install the Servomotor library by Gearotons from the Arduino Library Manager, or from Arduino_library/. Wire the board's UART to an RS-485 transceiver, then:

#include <Servomotor.h>

void setup() {
  Servomotor motor('X', Serial1);                  // alias 'X'; the port opens on first use
  motor.setPositionUnit(PositionUnit::SHAFT_ROTATIONS);
  motor.setTimeUnit(TimeUnit::SECONDS);
  motor.enableMosfets();
  motor.trapezoidMove(2.0f, 3.0f);                 // two rotations over three seconds
  delay(4000);
  Serial.println(motor.getPosition());             // where it actually is, from the encoder
}
void loop() {}

That is a trimmed Arduino_library/example_one_move.cpp (the full file adds the ESP32 RS-485 pin definitions).

Quick start (talk to it)

uvx --from servomotor-mcp servomotor-mcp        # runs with a simulated motor if no hardware is attached

Add it to Claude Desktop or run claude mcp add gearotons-motor -- uvx --from servomotor-mcp servomotor-mcp, then ask: "Find my motors, then move the one on the bench to 90 degrees and tell me where it ended up." Details and the full tool list: Gearotons/servomotor-mcp.

▶ 50-second video: the real motor and this session side by side (recorded 2026-09-09 on a bench M17).

What is in this repository

The command set is data-driven: every firmware command is defined once in motor_commands.json and the Python library, the Arduino library and the MCP server are generated from it, so they always agree.

Firmware 0.16.0.0

This backward-compatible M17 release adds Get PID constants (command 48). It returns the configured raw P, I and D values without changing controller or motion state. With the updated Python bindings in this repository:

p, i, d = m.get_pid_constants()

The release image targets M17 hardware 1.5, software compatibility code 3. See the release notes for the wire contract, upgrade/rollback commands, client requirements and test evidence.

Where the M17 is not the right tool

Direct-drive torque tops out at 0.65 N·m (gear it or go up a frame size for more), it is IP20 and indoor-only, and it is not a STEP/DIR drop-in for an existing 3D-printer board — it wants a serial bus and a host that sends it moves. We would rather you know that before you buy.

Community and support

Questions and builds: GitHub Discussions · email info@gearotons.com. Issues and pull requests welcome — the whole stack is here to be read, modified and improved.

Built and assembled by Gearotons in Shenzhen. MIT license — see LICENSE.