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Common Issues with EDDY Sensor

Error During Homing: Error during homing z: Eddy current sensor error​

When encountering this error, troubleshoot in order.

Update Klipper or System​

Important Notice

There was a compatibility issue with the Z homing function of EDDY, which has been optimized in the Klipper update on January 6, 2026.

  • For standard host computers: Update Klipper to a newer stable version.
  • For FLY host computers: Upgrade the system version to V1.3.5 or higher.

After the update, EDDY needs to be recalibrated.

Adjust Drive Current​

  1. Open the printer.cfg file.
  2. Locate the reg_drive_current = parameter at the bottom of the configuration.
  3. Increase or decrease the current value by 1, for example, change 15 to 16 or 14.
  4. Enter the calculated result directly. Do not use formulas like 15+1.
  5. Save the file and restart the printer, then retest homing.
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Adjust Probe Offset​

If updating and adjusting the drive current are ineffective, check descend_z.

  1. Find the [probe_eddy_current fly_eddy_probe] section in printer.cfg.
  2. Increase the descend_z: value appropriately. The default is usually 0.5. Try 2.0 or 2.5 first.
  3. This parameter should only appear once in this configuration section. Do not duplicate it.
  4. The recommended value should not exceed 3.0. The final value depends on the machine structure and probe installation height.
  5. Save and restart the printer, then test homing again.
Version Note

Klipper versions after March 2026 use descend_z in the [probe_eddy_current] configuration. The old z_offset parameter is deprecated and may be removed in future versions. If tutorials, old configurations, or screenshots still show z_offset, change it to descend_z.

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Amplitude Low/High warning Prompt​

Error Message: my_eddy_probe: Amplitude Low/High warning (36), Amplitude Low/High warning (48), etc. The number in parentheses is the measured amplitude value.

Common Causes:

  • The reg_drive_current setting is inappropriate, causing the sensor oscillation amplitude to be outside the ideal range.
  • The distance (standoff) between the probe and the heatbed is too large or too small.
  • The probe is loosely mounted, or the heatbed surface is uneven.

Solution:

  1. Re-calibrate the drive current: LDC_CALIBRATE_DRIVE_CURRENT CHIP=fly_eddy_probe, then SAVE_CONFIG.
  2. If warnings persist after calibration, manually fine-tune reg_drive_current (by ±1 each time) as described in the "Adjust Drive Current" section above.
  3. Check if the probe is firmly mounted. The gap between the probe bottom and the heatbed surface should ideally be between 0.3–1.0 mm.
  4. Ensure the heatbed is a flat metal surface without warping or bumps.
  5. If warnings occur only at specific positions, it might be due to local unevenness on the heatbed. Try recalibrating at different locations.

!! probe_eddy_current sensor not in valid range Prompt​

This error indicates that the probe reading is outside the valid range. A common cause is that after enabling the EDDY probe, the probing heights defined in other configuration sections are not being applied as expected, causing the probe to move beyond its physical range.

Please check the following locations:

  • [probe_eddy_current fly_eddy_probe]
  • [bed_mesh]
  • [z_tilt] or [quad_gantry_level]
  • Custom homing, leveling, or bed-mesh macros

Solution:

  1. Ensure the descent height for all probing actions is within the EDDY's usable range.
  2. Avoid having multiple macros or configuration sections override the same height parameter.
  3. After modification, save and restart Klipper, then re-run homing or leveling.
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Eddy I2C STATUS/DATA error or Invalid read data Prompt​

These errors indicate abnormal communication or readings between the EDDY sensor and the MCU.

Common Causes:

  • Poor contact in the EDDY wiring, connectors, or solder joints.
  • I2C line is too long, poor quality wiring, or running parallel to motor/heater wires causing interference.
  • I2C bus speed is too high for the current wiring and environment.
  • Unstable sensor power supply.

Solution:

Power Off Before Operation

Before re-plugging EDDY cables, rearranging wiring, or checking connectors, completely turn off and disconnect the printer power supply. Do not plug/unplug sensors or touch terminals while powered on.

  1. Power off, then re-seat the EDDY cable connections. Check for loose terminals.
  2. Route the EDDY communication cables away from motor, heater, and heatbed wires.
  3. If using hardware I2C, try lowering the I2C bus speed. If instability persists, test with software I2C.
  4. Prioritize cross-testing by replacing with a pre-made cable, changing ports, or swapping the sensor. For electrical testing of bare terminals, contact technical support or a professional.
  5. After modification, re-run homing or PROBE_EDDY_CURRENT_CALIBRATE.

Unable to obtain probe_eddy_current sensor readings Prompt​

This error means Klipper failed to get valid sensor data from the EDDY within the expected time.

Common Causes:

  • The sensor communication line is disconnected, or the configured bus/pin is incorrect.
  • The probe is too far from the metal bed surface, so the reading is out of range.
  • reg_drive_current is inappropriate, resulting in insufficient sensor frequency range.
  • Drive current calibration or Z-height calibration has not been completed.

Solution:

Power Off Before Operation

Before checking the EDDY bus, pin wiring, or replacing the sensor cable, completely turn off and disconnect the printer power supply. Do not plug/unplug the sensor while powered on.

  1. Power off, then verify that the bus and pin configurations in [probe_eddy_current fly_eddy_probe] match the actual wiring.
  2. Move the nozzle to the center of the heatbed, ensuring the EDDY is above the metal bed surface.
  3. Re-run LDC_CALIBRATE_DRIVE_CURRENT CHIP=fly_eddy_probe and then SAVE_CONFIG.
  4. Re-run PROBE_EDDY_CURRENT_CALIBRATE CHIP=fly_eddy_probe.
  5. If the error only occurs during homing, continue by adjusting reg_drive_current and descend_z as described in the "Error During Homing" section above.

MCU Protocol error: Unknown command i2c_write​

Error Messages: MCU Protocol error, mcu 'eddy': Unknown command: i2c_write, Command format mismatch.

These errors usually indicate a version mismatch between the EDDY/RP2040 peripheral MCU firmware and the Klipper running on the host computer. A common scenario is updating the host Klipper without recompiling and flashing the EDDY firmware. It could also mean the EDDY firmware is newer than the host Klipper, and the host doesn't recognize the new commands used by the peripheral firmware.

Solution:

  1. Check klippy.log for Git version and Loaded MCU 'eddy' ... version to confirm if the host Klipper and EDDY firmware are from the same version.
  2. Recompile and flash the firmware for the MCU connected to the EDDY. Refer to the documentation for the specific toolboard or EDDY product for flashing instructions.
  3. If using a third-party integrated system or a customized Klipper, first confirm that the system supports the current EDDY firmware. When in doubt, use the firmware package provided by that specific system.
  4. After flashing, execute FIRMWARE_RESTART, then re-run the EDDY drive current and height calibration.

General Version Check: MCU Protocol error

TAP Mode Trigger Issues​

When using EDDY's METHOD=tap, issues like premature stop, failure to stop after bed contact, or noticeable instability are often related to the tap_threshold and the state of the nozzle/bed surface.

Detailed Process: EDDY TAP Mode Debugging

Motion Risk

TAP testing brings the nozzle close to or in contact with the heatbed. Ensure the nozzle and bed are clean, keep hands and tools away from the motion area, and be ready to emergency stop.

Troubleshooting Points:

  1. Ensure the nozzle and bed surface are clean. Residue on the nozzle directly affects TAP results.
  2. Before starting TAP, the nozzle should be within a few millimeters of the bed surface, not too close or too far.
  3. If it stops before touching the bed, the tap_threshold might be too low. Increase it appropriately.
  4. If it doesn't stop after touching the bed, the tap_threshold might be too high. Stop immediately and decrease the threshold.
  5. After adjustment, re-run PROBE_EDDY_CURRENT_TAP_CALIBRATE. If successful, save the configuration with SAVE_CONFIG.

First Layer Instability Due to Thermal Drift​

EDDY is an eddy current sensor. Changes in the temperature of the bed, nozzle, sensor coil, and nearby metal parts can affect measurements. Symptoms usually include: calibration is normal when cold, but the first layer is either too high or too low during hot printing.

Solution:

  1. Perform EDDY calibration at temperatures close to the actual printing conditions.
  2. Before printing, allow the bed and nozzle temperature to stabilize before homing, leveling, or probing the bed mesh.
  3. If the EDDY sensor has a temperature sensor, configure [temperature_probe] and implement temperature drift compensation.
  4. For enclosed printers, it is recommended to let the chamber temperature stabilize before performing fine calibration.

descend_z Debugging Suggestion​

In many debugging cases, setting the initial value of descend_z in the [probe_eddy_current fly_eddy_probe] section to 2.5 allows many EDDY sensors to reach a working state more quickly.

Note

2.5 is a debugging starting point, not a universal fixed value or official default configuration. The optimal offset depends on the probe installation position, nozzle height, and machine structure. Please rely on actual calibration results.

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