A closed-loop stepper driver that bolts to the back of a NEMA 17. Every step measured, every axis on one CAN-FD bus.
Scroll through the board. Every part below sits where it does on the real PCB, straight from the CAD model.
An Arm Cortex-M4F with hardware floating point runs trajectory planning, position control and step generation 20,000 times a second, on a timer of its own, whatever else the firmware is doing.
An Arm Cortex-M4F with hardware floating point runs trajectory planning, position control and step generation 20,000 times a second, on a timer of its own, whatever else the firmware is doing.
Trinamic’s TMC2209 turns every step into smooth coil current: StealthChop when it can be silent, SpreadCycle when the motor needs the torque.
On the underside, right over the motor’s rear shaft, a 12-bit magnetic encoder measures 4,096 positions per turn. The loop always knows where the shaft really is, so a stall is caught instead of shifting your part.
A CAN-FD transceiver puts every S1 on one twisted pair: 2.5 Mbit/s data, up to 127 axes, and a jumper for the 120 Ω terminator on the last board.
Screw terminals for power (3.5 mm) and for motor, CAN and switches (2.54 mm), a JST PH for step/dir from any 3.3 V controller, and a 12-pin JST PHD for an external encoder.
Open-loop steppers trust that every step landed. The S1 checks, 20,000 times a second, and does something about it.
A 20 kHz position loop tracks the shaft through the on-board AS5600. A blocked axis is caught as a stall and stopped, never silently shifted.
Auto-tune runs the axis faster and faster until it slips, then keeps the fastest speed and acceleration that passed three times.
The TMC2209 runs StealthChop at low speed and switches to SpreadCycle when the motor needs the torque.
Home against a limit switch, or gently into a hard stop with reduced current. No switch needed.
Configure once over CAN, then drive it from any 3.3 V step/dir controller while it keeps the loop closed.
GPL-3.0 firmware built with PlatformIO, plus Python and Arduino C++ libraries and a browser control panel.
Tercio FD turns USB-C into CAN-FD. Daisy-chain S1 drivers and sensors along one twisted pair; each answers to its own ID and streams its state back.
CAN-FD · 2.5 Mbit/s
Up to 127 nodes on one bus
Tercio Control runs in Chrome or Edge and talks to the bus over Web Serial. Nothing to install: plug in, click connect.
from TercioBridge import Bus, Stepper, Unit
with Bus() as bus: # finds the Tercio FD
for info in bus.discover(): # every S1 on the bus
print(info)
x = Stepper(bus, 1, unit=Unit.DEGREES)
x.enable()
x.calibrate() # once per motor
x.move_to(90, wait=True)
print(x.position, x.telemetry.state)#include <TercioBridge.h>
// Any Stream connected to the Tercio FD.
Tercio::Bus bus(Serial1);
Tercio::Stepper x(bus, 1, Tercio::Unit::Degrees);
void setup() {
Serial1.begin(115200);
x.enable();
x.moveTo(90.0);
}
void loop() {
bus.poll(); // replies, telemetry and faults
}Python for your computer or a Raspberry Pi, C++ for Arduino-class boards. Positions in degrees, radians or turns; moves, homing and live telemetry in a few lines.
Closed-loop stepper driver
Launch price soon
USB-C to CAN-FD adapter
Launch price soon
Orientation on the CAN bus
Launch price soon
Rear shaft and encoder magnet fitted
Launch price soon
From the adapter to the first driver
Launch price soon
CAN, link, motor and power cables with ferrules for the S1’s screw terminals.
Tercio S1, Tercio FD and the cable between them. Add an S1-ready motor and you’re one USB cable away from your first closed-loop axis.
Anything else? The firmware, libraries and control panel are all on GitHub.
Orders open on 1 December 2026 at 00:00 GMT. Join the list and we’ll email you once, the moment the store opens.
Bipolar NEMA 17 steppers with a rear shaft: the on-board encoder reads a diametric magnet on it. Our S1-ready motors come with the magnet fitted. No rear shaft? Connect an external AS5048A or AS5600 encoder instead.
To set up an S1, or to control it over CAN from a computer, yes: the FD connects the bus to USB. Once set up, an S1 can also follow a step/dir controller by itself.
Yes, as a step/dir driver for controllers with 3.3 V logic. The STEP, DIR and EN inputs are not 5 V tolerant. The S1 keeps the loop closed while it follows your controller.
Chrome, Edge and other Chromium-based browsers on desktop, which support Web Serial. Nothing to install. The Python library works on any computer.
Up to 127 nodes, each with its own ID. Terminate both ends of the bus with 120 Ω: the Tercio FD has it built in and the S1 has a jumper for it.
The S1 firmware is GPL-3.0. It lives on GitHub alongside the Python and C++ libraries and the control panel. The hardware is designed by Tercio Labs.
Join the launch list and get 20% off your first order when the store opens.