Grafito CANStepper

Closed-loop stepper motor control over CAN. Each board carries an ESP32-C3, a TMC2209 driver, an MT6701 14-bit magnetic encoder and a CAN transceiver; up to 31 boards daisy-chain on one 1 Mbps bus and are driven from Python through the USB port of any board on the chain.

├── canstepper/                              # Python package (grafito-canstepper)
├── firmware/GrafitoCANStepper_C3/           # node firmware (GCSP v1, fw 1.12)
├── firmware/GrafitoCANStepper_C3_CANopen/   # optional CiA 301/402 SKU (fw 2.1)
├── examples/                                # runnable examples + machine.toml
├── tests/                                   # pytest suite (runs on a software sim)
├── model_assets/                            # assembly render, PCB drawing, STEP CAD
└── docs/                                    # protocol, quickstart, CAD index

Product links

• Shop / brochure: CANStepper Adapter Board
• Amazon (India): https://www.amazon.in/dp/B0H8XZ6V99
• Docs: https://docs.grafito.in
• Board test station: https://docs.grafito.in/dashboard
• Mechanical CAD & drawings: https://docs.grafito.in/docs/mechanical-cad
• PyPI: grafito-canstepper

CAD and brochure files in this repo (model_assets/):

V1 board assembly (click the preview to play the video):

This clip is version 1 of the same board. V1 used three different connector types, which made cabling and crimping difficult. The current production board is V2, with JST 2.0 connectors throughout for easy crimping.

Important — encoder magnet: Fit a diametrical magnet on the motor shaft. The magnet polarity must be radial, not axial. An axial magnet will not produce a valid MT6701 angle and closed-loop control will fail.

After USB and Vin are connected, test the board in the CANStepper Test Station — set the node ID, enable the driver, jog, and check encoder / TMC / CAN telemetry.

Highlights

• Layered Python API — raw frames → StepperNode → NodeGroup → Axis (mm units via rotation_distance) → DualMotorAxis / IndependentDualAxis / Cartesian / CoreXY / MotionGroup → declarative machine.toml.
• Safety scopes — node.estop(), group.estop(), bus.estop_all() (single broadcast frame); e-stop is latched until re-enabled.
• Homing — physical endstop on IO8, sensorless (StallGuard), or set-zero; configurable current, backoff and timeout.
• Closed loop — firmware ≥1.12 plans a rest-to-rest S-curve trajectory with velocity + acceleration feedforward and a light tracking PID on the MT6701 encoder (optional encoder LUT). All motion limits are configurable defaults, never hard clamps.
• On-bus leader/follower — dual-motor gantries stay coupled with no host in the loop (DualMotorAxis).
• Encoder-gated dual screws — IndependentDualAxis commands both motors independently and blocks the next pass until both encoders are within mm tolerance of the target.
• Simulator included — canstepper.sim.SimNetwork implements the whole protocol in software; the test suite and the examples run without hardware.

Install & first spin

pip install grafito-canstepper

# Development (from this directory):
# pip install -U pip setuptools && pip install -e ".[dev]"

from canstepper import CANStepperBus

with CANStepperBus.serial("/dev/ttyACM0") as bus:
    print(bus.discover())
    node = bus.node(1)
    node.set_run_current(40).enable()
    node.move_to(360.0, blocking=True)

Continue with:

• docs/quickstart.md — first motion
• docs/closed_loop_tuning.md — trapezoid + v_ff
• docs/protocol.md — GCSP v1 wire protocol
• docs/mechanical_cad.md — CAD, drawings, assembly video

G-code examples (from this directory):

PYTHONPATH=. python3 examples/gcode_cartesian.py /dev/ttyACM0 1 2
PYTHONPATH=. python3 examples/gcode_corexy.py /dev/ttyACM0 1 2
PYTHONPATH=. python3 examples/gcode_from_file.py examples/gcode/square.gcode

Homing examples (IO8 endstop, StallGuard sensorless, set-zero):

PYTHONPATH=. python3 examples/home_endstop.py /dev/ttyACM0 1 -1
PYTHONPATH=. python3 examples/home_sensorless.py /dev/ttyACM0 1 -1 60
PYTHONPATH=. python3 examples/home_set_zero.py /dev/ttyACM0 1

Belt axis (mm):

PYTHONPATH=. python3 examples/belt_move_mm.py /dev/ttyACM0 1 50 77.2 150

Development

python3 -m pytest

Current GCSP firmware is 1.12 (S-curve + Ka + LUT; motors off at boot until enable()). Optional CANopen 2.1 lives in firmware/GrafitoCANStepper_C3_CANopen/ with GrafitoCANStepper.eds and GrafitoCANStepper_Node1.dcf / GrafitoCANStepper_Node2.dcf (FileRevision 2, identity 0x00020100). Discard any older 2.0 EDS — it will not import this board. Node 2 must be flashed with -DCO_FACTORY_NODE_ID=2. See https://docs.grafito.in/docs/canopen. Do not mix GCSP and CANopen on one bus.

Firmware builds with Arduino IDE or arduino-cli (ESP32C3 Dev Module, USB CDC On Boot = Enabled; libraries: FastAccelStepper, TMC2209 janelia-arduino). Apply Vin (5–24 V, typically 24 V) before upload — USB-C is data only and does not power the ESP32 for programming. CAN termination is on by default (0 Ω jumper); remove that 0 Ω on mid-chain daisy-chain nodes.

arduino-cli compile --fqbn esp32:esp32:esp32c3:CDCOnBoot=cdc \
  firmware/GrafitoCANStepper_C3
arduino-cli upload -p /dev/ttyACM0 --fqbn esp32:esp32:esp32c3:CDCOnBoot=cdc \
  firmware/GrafitoCANStepper_C3