Sensorless Homing

Sensorless homing uses the TMC driver's DIAG signal to detect motor stall, replacing physical limit switches.

Prerequisites

All of the following conditions must be met:

1. The motherboard supports the DIAG function.
2. The driver supports DIAG signal output.
3. The corresponding limit switch port must not have any device connected.
4. The machine structure is suitable for sensorless homing, and moving parts will not be damaged when hitting the end stops.

Motherboard Compatibility Check

Type	Support Status	Representative Models	Operation Requirements
Class A	Default Direct Connection	Super / Gemini / CDY / E3 Series	Use the corresponding limit switch interface directly
Class B	Requires Jumper to Enable	D / C / Pro-X10 / Micro Series	Must install DIAG jumper cap
Class C	Not Supported	Fly-F407ZG	Cannot use sensorless homing function

Confirmation Method:

1. Check if the motherboard has a jumper socket labeled DIAG.
2. Refer to the schematic to confirm if the DIAG signal from the driver interface is connected to the limit switch port.
3. For most motherboards, Drive0 corresponds to io0, Drive1 corresponds to io1, and so on.

Class A Motherboards: No DIAG jumper, default direct connection to the corresponding limit switch port.

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Class B Motherboards: DIAG jumper required.

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Driver Compatibility Check

Tip

TMC5160, TMC2240, and TMC2130 usually have two DIAG pins. Please refer to the corresponding product documentation or consult customer service to confirm which pin to use.

Driver Model	Compatibility	DIAG Pin	Configuration Requirement	Sensitivity Range
TMC2209	Supported	Single Pin	Use diag_pin directly	0-255, 255 most sensitive, 0 least sensitive
TMC5160	Supported	Dual Pin	Select diag0_pin or diag1_pin	-64-63, -64 most sensitive, 63 least sensitive
TMC2240	Supported	Dual Pin	Select diag0_pin or diag1_pin	-64-63, -64 most sensitive, 63 least sensitive
TMC2130	Supported	Dual Pin	Select diag0_pin or diag1_pin	-64-63, -64 most sensitive, 63 least sensitive
TMC2208	Not Supported	-	Cannot use sensorless homing function	-
TMC2660	Not Supported	-	Cannot use sensorless homing function	-
LV8729	Not Supported	-	Cannot use sensorless homing function	-

Configuration Instructions

• Configuration needs to be modified according to the actual driver model and axis name.
• tmc2209 in tmc2209_stepper_x needs to be changed to the corresponding driver model.
• x in stepper_x represents the X axis. If configuring the Y axis, change it to stepper_y.
• On some machines, retraction during sensorless homing may cause homing to fail. Set homing_retract_dist to 0.

Reference Configuration

• TMC2209 Reference Configuration
• TMC5160 Reference Configuration
• TMC2130 Reference Configuration
• TMC2240 Reference Configuration

Notes:

• The pins below are for reference only; modify according to your actual motherboard.
• diag_pin usually requires adding ^, otherwise, homing may fail.
• driver_SGTHRS needs to be tested in practice; 255 is most sensitive, 0 is least sensitive.

printer.cfg

[stepper_x]
endstop_pin: tmc2209_stepper_x:virtual_endstop
position_endstop: 0
homing_retract_dist: 0

[tmc2209 stepper_x]
diag_pin: ^PD9
driver_SGTHRS: 100

Notes:

• The pins below are for reference only; modify according to your actual motherboard.
• Refer to the product manual to confirm whether to use diag0_pin or diag1_pin.
• driver_SGT needs to be tested in practice; -64 is most sensitive, 63 is least sensitive.

printer.cfg

[stepper_y]
endstop_pin: tmc5160_stepper_y:virtual_endstop
position_endstop: 0
homing_retract_dist: 0

[tmc5160 stepper_y]
diag1_pin: ^!PD9
driver_SGT: 1

Notes:

• The pins below are for reference only; modify according to your actual motherboard.
• Refer to the product manual to confirm whether to use diag0_pin or diag1_pin.
• driver_SGT needs to be tested in practice; -64 is most sensitive, 63 is least sensitive.

printer.cfg

[stepper_y]
endstop_pin: tmc2130_stepper_y:virtual_endstop
position_endstop: 0
homing_retract_dist: 0

[tmc2130 stepper_y]
diag1_pin: ^!PD9
driver_SGT: 1

Notes:

• The pins below are for reference only; modify according to your actual motherboard.
• Refer to the product manual to confirm whether to use diag0_pin or diag1_pin.
• driver_SGT needs to be tested in practice; -64 is most sensitive, 63 is least sensitive.

printer.cfg

[stepper_x]
endstop_pin: tmc2240_stepper_x:virtual_endstop
position_endstop: 0
homing_retract_dist: 0

[tmc2240 stepper_x]
diag1_pin: ^!PD9
driver_SGT: 1

Testing Sensitivity

Test Safety

When testing sensorless homing, the print head must be moved to the center of the machine, and be prepared to execute M112 emergency stop at any time. Do not test at high speed or unattended.

Step 1: Set Maximum Sensitivity

TMC2209:

SET_TMC_FIELD STEPPER=stepper_x FIELD=SGTHRS VALUE=255

TMC5160 / TMC2240 / TMC2130:

SET_TMC_FIELD STEPPER=stepper_x FIELD=sgt VALUE=-64

Step 2: Perform Single Axis Homing

G28 X

If the axis does not start moving, moves abnormally, or cannot stop, execute immediately:

M112

At this point, check the corresponding DIAG pin wiring, jumper cap, and configuration.

Step 3: Gradually Decrease Sensitivity

• TMC2209: Gradually decrease SGTHRS.
• TMC5160 / TMC2240 / TMC2130: Gradually increase sgt.
• After each adjustment, re-execute SET_TMC_FIELD and the single-axis homing test.

The goal is to find the highest reliable sensitivity that allows the carriage to move steadily to the end stop and stop.

Step 4: Write Back Configuration

After finding the appropriate value through testing, write it back to the corresponding driver configuration in printer.cfg.

If there is still a noticeable impact sound, clicking sound, or unstable triggering at maximum sensitivity, it usually indicates that the homing speed is too low, the driver current is too low, there is abnormal mechanical resistance, or the axis is unsuitable for sensorless homing.