Pin Configuration

Note

• This page lists the pin configuration of the FLY-Gemini V3 motherboard after flashing Klipper firmware. The pin numbers are based on the motherboard schematic.
• UART/CS is the driver communication pin: when using TMC2209, it functions as UART; when using SPI drivers like TMC5160, it serves as the chip select CS pin. The same pin is multiplexed.
• EN is the enable pin. In Klipper configuration, it is typically active low (enable_pin with the ! prefix).
• DIAG is the driver diagnostic signal pin. When using sensorless homing, configure the corresponding diag_pin according to the table below.

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Driver Pins

The FLY-Gemini V3 provides 4 driver ports:

Driver	STEP	DIR	EN	UART/CS	DIAG
DRIVER0	PC13	PC1	PA3	PB11	PA4
DRIVER1	PC14	PC4	PD2	PC10	PA5
DRIVER2	PC15	PC5	PC12	PB7	PA6
DRIVER3	PC3	PC8	PC11	PB6	PB1

Power Off Before Operation

Before starting, completely shut down the printer and disconnect the power supply. Do not plug or unplug wiring harnesses, rearrange interface wiring, or touch terminals while the power is on.

DIAG and Sensorless Homing

When using sensorless homing, the driver chip outputs a stall detection signal through the DIAG pin, which Klipper needs to read via the corresponding input port. The correspondence between the DIAG pins and the limit switch ports on this motherboard is as follows:

• DRIVER0–3: The DIAG pins are directly connected to the corresponding limit switch input ports on the main controller (DRIVERn → Limit Port n). There are no DIAG jumper pins on the board; the DIAG signal is always delivered to the main controller. When enabling sensorless homing, directly configure the corresponding limit switch port pin as the diag_pin. Do not connect a physical limit switch to that limit port.

Once sensorless homing is enabled, the corresponding limit port is occupied by the DIAG signal and must not be connected to a mechanical or optical limit switch simultaneously.

SPI Bus

SPI drivers such as the TMC5160 use the motherboard's hardware SPI bus. In the configuration, simply set spi_bus: spi3 — there is no need to configure the MOSI/MISO/SCLK pins separately:

[tmc5160 stepper_x]
spi_bus: spi3
cs_pin: UART/CS pin of the corresponding driver

For detailed information on software SPI and SPI speed, refer to: SPI Configuration Method

Endstops and Probe

Function	Pin	Corresponding Driver DIAG
Endstop Port 0 / IO0	PA4	DRIVER0
Endstop Port 1 / IO1	PA5	DRIVER1
Endstop Port 2 / IO2	PA6	DRIVER2
Endstop Port 3 / IO3	PB1	DRIVER3
Probe	PA1	-

Heating

Function	Pin
Heater Port 0	PA0
Heated Bed	PA2

Temperature Sensors

Function	Pin
Thermistor Port 0	PC0
Thermistor Port 1	PC2

Supported Thermistor Types

The thermistor ports support NTC thermistors (100K) by default. The recommended sensor_type configuration is Generic 3950.

For the list of built-in sensor_type options in Klipper that can be connected directly and their applicable scenarios: Thermistor Configuration Method

K-type thermocouples, PT100, and others require additional signal conversion chips and cannot be connected directly to the thermistor ports.

Fans

Function	Pin
Fan Port 0	PC6
Fan Port 1	PC7

PWM

The FLY-Gemini V3 provides 1 PWM output channel, which can be used for servos, fan speed control, etc.:

Pin	Remarks
PB0	Servo / BLTouch control

BL-Touch

Function	Pin
Servo Signal	PB0
Probe Signal	PA1