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My-Cloner Rev A — Motors & Homing

This page describes the stepper motor architecture, driver assignments and homing strategy used by the My-Cloner Rev A.

The printer uses:

  • 5 × stepper motors
  • 5 × TMC2209 stepper drivers
  • UART communication
  • Sensorless homing on X and Y
  • P.I.N.D.A. probe for Z reference

Physical Validation Required

Motor direction, current, sensorless-homing sensitivity and homing repeatability must be validated on the physical My-Cloner Rev A.

Configuration values must not be considered final until the machine has completed the bring-up and validation process.

Motor Architecture

The My-Cloner Rev A uses five stepper motors.

Function Motor Type Board Driver Klipper Section
X Axis NEMA17 X [stepper_x]
Y Axis NEMA17 Y [stepper_y]
Left Z Axis NEMA17 Z [stepper_z]
Right Z Axis NEMA17 E1 [stepper_z1]
Extruder NEMA17 Pancake E0 [extruder]

The Z axis uses two independent motors.

The current Rev A board assignment is:

graph LR
    ZDRV[Z Driver] --> ZL[Left Z Motor]
    E1DRV[E1 Driver] --> ZR[Right Z Motor]

This assignment will be physically validated during machine bring-up.

graph TD
    BOARD[MKS Robin Nano V3]

    XDRV[X Driver<br/>TMC2209]
    YDRV[Y Driver<br/>TMC2209]
    ZDRV[Z Driver<br/>TMC2209]
    E0DRV[E0 Driver<br/>TMC2209]
    E1DRV[E1 Driver<br/>TMC2209]

    XM[X Axis Motor]
    YM[Y Axis Motor]
    ZLM[Left Z Motor]
    EXT[Extruder Motor]
    ZRM[Right Z Motor]

    BOARD --> XDRV
    BOARD --> YDRV
    BOARD --> ZDRV
    BOARD --> E0DRV
    BOARD --> E1DRV

    XDRV --> XM
    YDRV --> YM
    ZDRV --> ZLM
    E0DRV --> EXT
    E1DRV --> ZRM

Stepper Drivers

The My-Cloner Rev A uses:

5 × TMC2209

The drivers are intended to operate in:

UART mode

This allows Klipper to configure and monitor driver parameters directly.

The Robin Nano V3 provides individual UART lines for each driver position.

Driver UART Pin
X PD5
Y PD7
Z PD4
E0 PD9
E1 PD8

These assignments are documented in the My-Cloner I/O Map.

Driver Configuration

The final TMC2209 configuration will include parameters such as:

  • UART pin
  • Motor current
  • Interpolation
  • StealthChop / SpreadCycle behaviour where appropriate
  • StallGuard configuration
  • Sensorless-homing sensitivity

Example structure:

[tmc2209 stepper_x]
uart_pin: PD5
run_current: TBD
diag_pin: TBD
driver_SGTHRS: TBD

Do Not Copy Example Values

Driver-current and StallGuard values depend on the actual motors and mechanical system.

These values must be determined during physical testing.

STEP / DIR / ENABLE Mapping

X Axis

Signal MCU Pin
STEP PE3
DIR PE2
ENABLE PE4
UART PD5
DIAG / Endstop PA15

The final direction polarity will be determined during motor testing.

Y Axis

Signal MCU Pin
STEP PE0
DIR PB9
ENABLE PE1
UART PD7
DIAG / Endstop PD2

The final direction polarity will be determined during motor testing.

Left Z Axis

Signal MCU Pin
STEP PB5
DIR PB4
ENABLE PB8
UART PD4

The Left Z motor uses the board's standard Z driver position.

Right Z Axis

Signal MCU Pin
STEP PD15
DIR PA1
ENABLE PA3
UART PD8

The Right Z motor uses the board's E1 driver position.

In Klipper this will be configured as:

[stepper_z1]

Independent Z Motors

The two Z motors are controlled independently by Klipper.

This allows separate motor control while still operating as one Z axis.

Extruder

Signal MCU Pin
STEP PD6
DIR PD3
ENABLE PB3
UART PD9

The extruder uses the E0 driver position.

X and Y Sensorless Homing

The My-Cloner Rev A does not use physical X or Y endstop switches.

Instead, the X and Y axes are planned to use:

TMC2209 sensorless homing

Sensorless homing detects the mechanical end of travel using the driver's StallGuard functionality.

The Robin Nano V3 routes the TMC2209 DIAG signals to the endstop inputs.

Axis DIAG / Endstop MCU Pin
X X- PA15
Y Y- PD2 
graph LR
    XMotor[X Axis Motor] --> XDriver[TMC2209 X]
    XDriver -->|StallGuard| XDiag[X DIAG]
    XDiag -->|PA15| MCU[MKS Robin Nano V3]

    YMotor[Y Axis Motor] --> YDriver[TMC2209 Y]
    YDriver -->|StallGuard| YDiag[Y DIAG]
    YDiag -->|PD2| MCU

Sensorless Homing Parameters

Sensorless homing requires physical tuning.

The main variables include:

  • Motor current
  • driver_SGTHRS
  • Homing speed
  • Belt tension
  • Mechanical friction
  • Axis mass
  • Acceleration
  • Homing direction

A configuration that works on another printer must not be assumed to work correctly on the My-Cloner.

Too Sensitive

If the StallGuard threshold is too sensitive, the axis may stop before reaching the mechanical end.

Not Sensitive Enough

If the threshold is not sensitive enough, the motor may continue pushing against the frame after reaching the mechanical end.

The value must therefore be tuned conservatively.

Sensorless Homing Validation

The recommended validation process for each sensorless axis is:

  1. Confirm free mechanical movement.
  2. Verify motor direction at low speed.
  3. Confirm TMC2209 UART communication.
  4. Configure a conservative motor current.
  5. Configure the DIAG pin.
  6. Start with a conservative StallGuard threshold.
  7. Test homing at low speed.
  8. Adjust sensitivity gradually.
  9. Repeat homing multiple times.
  10. Confirm repeatability.

The final configuration should only be accepted when homing is reliable and repeatable.

Homing Direction

The final X and Y homing directions must match the My-Cloner mechanical design.

The direction will be validated against:

  • Axis geometry
  • Motor direction
  • Belt routing
  • Coordinate system
  • Printable-area origin

The Klipper dir_pin polarity may therefore require inversion during bring-up.

Pin Inversion

In Klipper, the ! prefix is used to invert a digital signal.

Example:

dir_pin: !PE2

The required polarity must be determined from the actual motor movement.

Z Homing

The Z axis does not use TMC sensorless homing.

The My-Cloner Rev A uses a:

P.I.N.D.A. inductive probe

The probe provides:

  • Z reference
  • Bed probing
  • Bed-mesh measurements
graph TD
    PINDA[P.I.N.D.A. Probe] -->|Z Reference| MCU[MKS Robin Nano V3]
    MCU --> KLIPPER[Klipper]

    KLIPPER --> ZDRV[Z Driver]
    KLIPPER --> E1DRV[E1 Driver]

    ZDRV --> ZL[Left Z Motor]
    E1DRV --> ZR[Right Z Motor]

The final board input used by the P.I.N.D.A. is still pending electrical validation.

Z Motor Behaviour

Both Z motors move together during normal operation.

Klipper will configure them as:

[stepper_z]

and:

[stepper_z1]

The P.I.N.D.A. probe provides the Z reference used by the Z axis.

Z Motor Direction

Both Z motors must move the gantry in the same physical direction.

Depending on motor orientation and wiring, one motor may require reversed direction.

Verify both motors independently before performing normal Z moves.

Motor Direction Validation

Before homing any axis:

  1. Position the carriage away from the mechanical end.
  2. Command a small positive move.
  3. Observe the physical direction.
  4. Stop immediately if the direction is incorrect.
  5. Correct the Klipper direction polarity or motor wiring.
  6. Repeat with a small move.
  7. Validate each motor independently.

For the Z axis, test Left Z and Right Z independently before operating them together.

Motor Current

The final TMC2209 current values are not yet defined.

Motor current must be selected according to:

  • Motor rated current
  • Driver cooling
  • Mechanical load
  • Required torque
  • Operating temperature
  • Reliability

The final current values will be recorded after physical validation.

Motor run_current Status
X TBD Pending validation
Y TBD Pending validation
Left Z TBD Pending validation
Right Z TBD Pending validation
Extruder TBD Pending validation

Microstepping

The generic Robin Nano V3 Klipper configuration uses:

microsteps: 16

This is a suitable starting point for the Rev A configuration.

The final configuration must remain consistent with:

  • TMC2209 settings
  • Pulley geometry
  • Belt pitch
  • Lead-screw geometry
  • Extruder geometry

Mechanical Transmission

X and Y

The My-Cloner X and Y axes use belt-driven motion.

The final Klipper rotation_distance depends on:

  • Belt pitch
  • Pulley tooth count
  • Motor step angle

This value will be confirmed against the actual My-Cloner mechanical configuration.

Z

The Z axis uses two lead screws.

The final Z rotation_distance must match the installed lead-screw geometry.

Extruder

The extruder rotation_distance must be calibrated physically.

The generic Klipper value must not be treated as the final My-Cloner value.

Bring-Up Sequence

The recommended motor bring-up sequence is:

  1. Validate controller power.
  2. Validate USB / MCU communication.
  3. Confirm TMC2209 UART communication.
  4. Test X motor direction.
  5. Test Y motor direction.
  6. Test Left Z motor direction.
  7. Test Right Z motor direction.
  8. Test extruder motor direction.
  9. Configure motor currents.
  10. Configure X sensorless homing.
  11. Configure Y sensorless homing.
  12. Validate P.I.N.D.A. input.
  13. Validate Z homing.
  14. Test repeated homing cycles.

Do not attempt a full automatic homing sequence until each subsystem has been tested individually.

Validation Status

Item Status
X motor board mapping Source confirmed
Y motor board mapping Source confirmed
Left Z board mapping Source confirmed
E0 / Extruder mapping Source confirmed
E1 / Right Z mapping Rev A assignment
TMC2209 UART pins Source confirmed
X sensorless architecture Planned
Y sensorless architecture Planned
Z homing architecture Defined — P.I.N.D.A.
Motor directions Pending validation
Motor currents Pending validation
X StallGuard threshold Pending validation
Y StallGuard threshold Pending validation
Homing speeds Pending validation
Homing repeatability Pending validation
Z motor synchronization Pending validation
Extruder rotation distance Pending calibration

For the complete board mapping:

I/O Map

For the controller:

Controller Board

For the Z probe and temperature sensors:

Heaters & Temperature Sensors

For the future Klipper configuration:

Firmware Configuration