Closed-loop stepper driver
Bolts to a NEMA 17, reads the shaft with an on-board encoder and runs a 20 kHz position loop. CAN-FD or step/dir.
Start here
Introduction
Tercio is a family of small modules for motion that share one CAN-FD bus. A Tercio S1 turns a stepper motor into a closed-loop servo axis, the Tercio FD connects the bus to your computer, and the Tercio IMU adds orientation on the same wires.
- 20kHz
- Position loop on every S1
- 127
- Nodes on one bus
- 2.5Mbit/s
- CAN-FD data rate
- 1000Hz
- Telemetry from each driver
The modules
Section titled “The modules”
USB-C to CAN-FD adapter
The bridge from your computer to the bus. Works with Tercio Control in the browser, Python and Arduino.
Orientation on the bus
A quaternion, roll, pitch and yaw at 100 Hz, zeroed where you like, on the same bus as your motors.
How it fits together
Section titled “How it fits together”ComputerTercio Controlor Python, Arduino
USB-C
AdapterTercio FD120 Ω built in
CAN
Node 1Tercio S1J9 open
CAN
Node 2Tercio S1J9 open
CAN
Node 3Tercio S1J9 jumper fitted
Every driver on the bus has a node ID from 1 to 127. The computer sends commands through the Tercio FD to one node or to all of them at once, and each driver streams its state back. The adapter only forwards frames, so the same bus works with the browser control panel, Python, an Arduino, or your own code.
What you need
Section titled “What you need”- A Tercio S1One per motor.
- A stepper motor with an encoder magnetBipolar, four wires, with a diametric magnet on its rear shaft. S1-ready motors have it fitted; otherwise see Mounting.
- A Tercio FD and a USB-C cableYour computer’s way onto the bus.
- A 12–28 V DC supply24 V is a good choice. Each S1 needs power; the bus does not carry it.
- CablesCAN cable from the adapter to the first driver, a motor cable and a power lead. The Starter Kit has the S1, the FD and the CAN cable.
- A computerChrome or Edge for Tercio Control, or Python 3.
Three ways to drive a motor
Section titled “Three ways to drive a motor”Tercio ControlIn the browser, nothing to install. Plug in the adapter, open the page, connect. Best for setup, tuning and trying things out.Read more
Your codeThe Python library on a computer, or the Arduino library on a board with USB host, such as a Teensy 4.1. Best for machines and experiments.Read more
Step/dirFrom a printer or CNC board. Configure the S1 once over CAN; then it follows STEP and DIR pulses with the loop closed.Read more
Good to know
Section titled “Good to know”Units are turnsOn the wire, positions are turns of the encoder shaft, speeds turns/s, accelerations turns/s². Tercio Control and the libraries convert to degrees or radians for you.
Firmware v2, protocol v2These docs describe firmware v2 on the S1 and the FD. Protocol v2 does not talk to the first firmware: update both ends together. Tercio Control shows the version on each motor’s Diagnostics tab.