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FLY-EDDY Wiring

The FLY-EDDY connects to the toolhead board or mainboard via the I2C interface. The 5P cable assembly contains 4 I2C signal wires (VCC, GND, SDA, SCL) and 1 temperature detection wire (TEMP, onboard thermistor). Both models have identical signal definitions but are adapted for different platforms:

  • EDDY-F (FPC cable): Specifically adapted for the EDDY interface on the SHT36 V3, SB2040 V3, and SB2040 PRO V3 toolhead boards
  • EDDY-M (MX1.25 connector): Adapted for standard toolhead boards or mainboards, connected via the I2C interface. Specific I2C configuration must follow the actual mainboard definitions (see the I2C explanation below)

Cable Specifications​

ModelCableSpecification
EDDY-MRibbon cable - single-ended MX1.255P (VCC / GND / SDA / SCL / TEMP), 30cm
EDDY-FFPC cable5P (VCC / GND / SDA / SCL / TEMP), 0.5mm pitch, same-side contacts, optional 150mm / 200mm

I2C Pinout​

PinDefinitionDescription
VCCPower positive5V power supply
GNDPower groundCommon ground with MCU
SDAI2C data lineConnect to the MCU's I2C SDA pin
SCLI2C clock lineConnect to the MCU's I2C SCL pin
TEMPTemperature detectionOnboard thermistor output, connect to the MCU's ADC pin for [temperature_probe] thermal drift compensation (optional)
  • EDDY-M: MX1.25 connector pinout (left to right) is SDA, TEMP, SCL, 5V, GND
  • EDDY-F: The FPC cable is only compatible with the EDDY interface on FLY toolhead boards (SHT36 V3 / SB2040 V3 / SB2040 PRO V3); plug it in directly, no need to verify the pinout
I2C Signal Line Precautions

SDA / SCL are open-drain signals. Do not connect capacitors (such as filter capacitors or decoupling capacitors), inductors, diodes, or other components in series or parallel on these signal lines. Do not route them through RC / LC filter circuits or external level shifters, as this will alter the signal rising edge timing and cause unstable I2C communication or errors.

The FLY-EDDY I2C address is fixed at 0x42 (42), corresponding to the configuration item i2c_address: 42.

Wiring Steps​

Power Off

Before starting wiring, completely turn off the printer and disconnect the power supply. Do not plug or unplug wire harnesses, adjust connector wire order, or touch terminals while powered on.

  1. Insert the MX1.25 cable into the EDDY-M terminal block, matching the terminal wire order one-to-one (from left to right: SDA, TEMP, SCL, 5V, GND)
  2. Connect the other end of the harness to the I2C interface on a standard tool board or mainboard, and verify the pin order against the interface silkscreen
  3. Connect the TEMP wire to an unused ADC pin on the mainboard; if no ADC pin is available, it can be left unconnected, but the temperature drift compensation function will be unavailable
  4. After inserting the terminal firmly, gently pull the harness to confirm it will not come loose, and route the wiring to avoid hanging or tension
I2C Configuration Notes

When EDDY-M is connected to a standard tool board or mainboard, i2c_mcu and i2c_bus must be filled in according to the actual mainboard MCU definition; when using software I2C, i2c_software_scl_pin / i2c_software_sda_pin must be specified. The I2C address is fixed at 0x42 (42), and the crystal frequency is 40MHz.

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Connecting EDDY-M to SHT36 V3 Tool Board​

When connecting EDDY-M to the SHT36 V3 tool board, software I2C is used: SCL connects to gpio20 (HV-IN), SDA connects to gpio22 (Probe):

High-Voltage Limit Jumper Cap

gpio20 is the HV-IN high-voltage limit port. Before use, the high-voltage limit jumper cap on the board must be connected; otherwise, the pin will not work properly and EDDY will not be recognized.

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Corresponding software I2C configuration:

[probe_eddy_current fly_eddy_probe]
i2c_mcu: SHT36
i2c_software_scl_pin: SHT36:gpio20
# SCL connects to HV-IN (gpio20); the high-voltage limit jumper cap must be connected first
i2c_software_sda_pin: SHT36:gpio22
# SDA connects to Probe (gpio22)

Pin Comparison of the Two Connection Methods​

SignalEDDY-M (MX1.25 Terminal)EDDY-F (FPC Cable)Tool Board / Mainboard Interface
Power Positive5V5V5V / VCC
Power GroundGNDGNDGND
Data LineSDASDASDA (connects to gpio22 when using SHT36 V3)
Clock LineSCLSCLSCL (connects to gpio20 when using SHT36 V3; high-voltage limit jumper cap must be connected first)
Temperature DetectionTEMPTEMPADC pin (gpio28 when EDDY-F connects to SHT36 V3)

The MX1.25 terminal wire order of EDDY-M (from left to right): SDA, TEMP, SCL, 5V, GND; the FPC cable of EDDY-F is only compatible with the FLY tool board EDDY interface, so no wire order verification is needed. When EDDY-M connects to SHT36 V3, software I2C is used: SCL connects to gpio20 (HV-IN), SDA connects to gpio22 (Probe). See the "Connecting EDDY-M to SHT36 V3 Tool Board" section above for details.

Cable Routing Recommendations​

  • EDDY communication cables should be kept away from motor cables, heater cables, and heated bed cables to avoid I2C signal interference
  • I2C cables should not be excessively long; poor cable quality or excessive routing length may cause unstable communication
  • When routing must cross power cables, try to cross them perpendicularly

Post-Wiring Verification​

After completing the wiring and confirming all connectors are firmly inserted, power on for verification:

  1. Perform drive current calibration: LDC_CALIBRATE_DRIVE_CURRENT CHIP=fly_eddy_probe
  2. Successful calibration completion indicates normal I2C communication; proceed with height calibration
  3. If I2C errors such as BUS_TIMEOUT or Invalid read data occur, power off first to inspect the wiring, then refer to the I2C configuration items to adjust the bus speed

I2C Error Troubleshooting: EDDY Issue Collection

I2C Configuration Item Explanation: EDDY I2C Pin and Configuration Explanation

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