Pin Distribution

Note

• This page lists the pin distribution of the FLY-Micro4 mainboard after flashing Klipper firmware. Pin numbers are based on the mainboard schematic.
• UART/CS is the driver communication pin: used as UART with TMC2209, or as chip select CS with SPI drivers such as TMC5160. The same pin is shared for both functions.
• EN is the enable pin. In Klipper configuration, it is typically active-low (with ! prefix in enable_pin).
• 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-Micro4 provides 4 driver ports:

Driver	STEP	DIR	EN	UART/CS	DIAG
DRIVER0	gpio6	gpio3	gpio7	gpio9 (address 0)	gpio13
DRIVER1	gpio1	gpio0	gpio2	gpio9 (address 1)	gpio14
DRIVER2	gpio26	gpio25	gpio27	gpio9 (address 2)	gpio15
DRIVER3	gpio23	gpio22	gpio24	gpio9 (address 3)	gpio12

Power Off Before Operation

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

DIAG and Sensorless Homing

In the table, rows where the Corresponding Driver DIAG is not - indicate that the driver's DIAG signal is connected to the corresponding input pin on the main controller. When enabling sensorless homing, configure diag_pin directly according to the table. The corresponding input pin will be occupied by the DIAG signal; do not connect mechanical or optical endstop switches to it simultaneously.

Endstops and Probe

Function	Pin	Corresponding Driver DIAG
Endstop port 0 / IO3	gpio12	DRIVER3
Endstop port 1 / IO2	gpio13	DRIVER0
Endstop port 2 / IO1	gpio14	DRIVER1
Endstop port 3 / IO0	gpio15	DRIVER2
Probe / IO4	gpio18	-

Heating

Function	Pin
Heater port 0	gpio20
Heater port 1	gpio21

Temperature Sensors

Function	Pin
Thermistor port 0	gpio28
Thermistor port 1	gpio29

Supported Thermistor Types

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

List of built-in sensor_type options in Klipper that can be directly connected, along with their applicable scenarios: Thermistor Configuration Method

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

Fans

Function	Pin
Fan port 0	gpio16
Fan port 1	gpio17

PWM

The FLY-Micro4 provides 3 PWM output channels, which can be used for servos, fan speed control, etc.:

Pin	Remarks
gpio10	Laser
gpio11	RGB / Neopixel
gpio19	Servo / BLTouch control

BL-Touch

Function	Pin
Servo signal	gpio19
Probe signal	gpio18

RGB

Function	Pin
RGB / Neopixel	gpio11

Display / EXP Notes

Interface Notes

The FLY-Micro4 does not provide standard EXP1 / EXP2 12864 pin headers. Please use the dedicated interfaces listed on this page for drivers, endstops, BL-Touch, RGB, Laser, etc. Do not apply the EXP1 / EXP2 pin tables from other mainboards.