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Catalyst.K ToolHead

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Introduction

Catalyst.K ToolHead is a compact Klipper toolboard with a footprint of only 47 mm × 44 mm, designed to be mounted close to the printhead or extruder. It is powered by an STM32G431CBT6 32‑bit MCU and supports multiple communication modes, including USB and CAN / RS‑232, which can be switched via an on‑board physical button.
The board integrates a TMC2209 stepper motor driver, an ADXL345 3‑axis accelerometer, multiple fan and temperature inputs, as well as BL‑Touch and hotend heater control. This greatly simplifies toolhead wiring, reduces cable bundle weight on moving parts, and improves overall reliability and serviceability of the printer.

Features

  • Compact toolboard design: 47 mm × 44 mm, mounted directly near the printhead or extruder to greatly simplify wiring.
  • STM32G431 MCU: 32‑bit high‑performance controller optimized for Klipper multi‑MCU setups.
  • Multiple communication modes: Supports USB, CAN, and RS‑232, switchable via on‑board button.
  • On‑board USB hub: Provides 3× USB ports and 1× CAN port for easy host and expansion connectivity.
  • Integrated TMC2209: On‑board 24V‑powered TMC2209 stepper driver for silent, precise extruder control.
  • Built‑in ADXL345: On‑board 3‑axis accelerometer for Klipper input shaping and resonance testing.
  • Stable power outputs: 24V input (max. 28V) with on‑board 5V@3A and 3.3V@0.8A rails.
  • Rich IO and fan interfaces: 4 level‑shifted IO pins, 4 fan outputs (2×2‑wire with selectable 5V/24V, 1×3‑wire, 1×4‑wire).
  • Complete sensing and actuator interfaces: 3 temperature inputs, 1 BL‑Touch connector, 1 hotend heater output up to 2.5A.
  • Easy debugging: On‑board BOOT0 and RESET buttons for quick flashing and debugging.

Applications

  • Used as a Klipper toolhead board for extruder/printhead control, providing local motor drive, temperature control, fan control, and acceleration measurement on the toolhead to greatly simplify the printer’s wiring.
  • Suitable for mid‑ to high‑end FDM 3D printers that require integrated TMC2209, ADXL345, BL‑Touch, and multiple fan/temperature interfaces, both for upgrading existing machines and for new printer designs.
  • Applicable in multi‑toolhead, multi‑nozzle, or remote‑extrusion setups as a distributed toolboard node, connected to the Klipper host system via CAN or USB /RS‑232 to build flexible multi‑MCU motion control architectures.

Hardware Specifications

Item Specification
Product name Catalyst.K ToolHead
Board size 47 mm × 44 mm
MCU STM32G431CBT6, 32‑bit ARM Cortex‑M4
Communication modes USB, CAN, RS‑232 (selectable via on‑board button)
Input voltage 24 V DC (max. 28 V)
On‑board power rails 5 V @ 3 A, 3.3 V @ 0.8 A
Stepper driver On‑board TMC2209, 24 V supply
Accelerometer On‑board ADXL345 3‑axis accelerometer
Level‑shifted IO 4× IO with voltage translators (selectable by pads)
Fan outputs 4 digital fan outputs: 2×2‑wire (5V/24V jumper‑selectable), 1×3‑wire, 1× 4‑wire
Temperature inputs 3× temperature sensor inputs
Probe interface 1× BL‑Touch connector
Heater output 1× hotend heater output, up to 2.5 A
On‑board buttons BOOT0 button, RESET button

Physical Connections

Pin Out

python Copy 
IO.0: PC14
IO.1: PB13
IO.2: PB14
IO.3: PB15

FAN0_PWCTL: PB3
FAN0_PWM: PB10
FAN0_TACH: PB11

FAN1: PA2
FAN1_TACH: PA8 
FAN2: PA4
FAN3: PA3

Heat: PC15
Thermistor (4.7k pull up): PB2
Thermistor (4.7k pull up): PB1
Thermistor (4.7k pull up): PB0
Thermistor next to TMC2209 (4.7k pull up) : PB12

Driver_EN: PB9
Driver_DIR: PB6
Driver_STEP: PB7
Driver_UART: PA15
Driver_DIAG: PA13

ADXL345
spi_bus: spi1
adxl345_cs_pin: PA0
adxl345_spi_software_sclk_pin: PA5
adxl345_spi_software_miso_pin: PA6
adxl345_spi_software_mosi_pin: PA7

USB_DM/CAN_RX: PA11
USB_DP/CAN_TX: PA12

Signal_PWM: PC13

Description Of Connections

Note

Radar function is not currently supported.

Connector Pin Default function Altermate
Power Input RS-232 (PA9,PA10)
CANBUS (PA11,PA12)		 Power and communication input, RS-232 and CANBUS are optional, which can be switched via an on‑board physical button. I/O
Fan0 FAN0_PWR: PB3
FAN0_PWM:PB10
FAN0_TACH: PB11		 Mosfet Output, For 4 pins Fan, voltage = 24V
Fan1 FAN1: PA2
FAN1_TACH: PA8		 Mosfet Output, For 3 pins Fan, Default voltage = 24V
Fan2 PA4 Mosfet Output, For 2 pins Fan, Default voltage = Depending on voltage selector.
(Header voltage selector)
Fan3 PA3 Mosfet Output, For 2 pins Fan, Default voltage = Depending on voltage selector.
(Header voltage selector)
IO.0 PC14 Digital Input, For endstop, Micro switch or Hall
(Pad voltage selector)		 Digital Output
IO.1 PB13 Digital Input, For endstop, Micro switch or Hall
(Pad voltage selector)		 Digital Output
IO.2 PB14 Digital Input, For endstop, Micro switch or Hall
(Pad voltage selector)		 Digital Output
IO.3 PB15 Digital Input, For endstop, Micro switch or Hall
(Pad voltage selector)		 Digital Output
TOUCH PWM:PC13
Z-MIN:PB15		 5V Digital Output, Digital Input, For Z probe, Proximity switch or Klicky, etc.
(Pad voltage selector)		 Digital Input
T0 PB2 ADC input, 4.7K pull-up, temperature measure Analog signal Input
T1 PB1 ADC input, 4.7K pull-up, temperature measure Analog signal Input
T2 PB0 ADC input, 4.7K pull-up, temperature measure Analog signal Input
HEAT PC15 Mosfet Output, Heating rod control, 2.5A Max
MOTOR For two-phase stepper motor,24V
USB1, USB3 Connected to the CH334P HUB chip, up to 4 USB2.0 devices (USB/USB1/MCU/USB3)

Connection

Simply connect our motherboard (CATALYST.K) to the Raspberry Pi's header power port and USB port using a power cable and data cable (USB to Type-C), respectively, as shown in the diagram below. No additional power supply is required for the Raspberry Pi, as our motherboard provides 5V@6A power output—more than sufficient to ensure the Raspberry Pi operates normally.

USB Communication Mode (Recommend)

  1. Connect the RS-232 connector (XH2.54-4) on the main board (CATALYST.K) to the power connector (J1) on the tool board (Catalyst.K ToolHead)
  2. Connect the USB connector (USB4) on the main board (CATALYST.K) to the connector (J4) on the tool board (Catalyst.K ToolHead).
  3. Connect J23 on the tool board (Catalyst.K ToolHead) to the Cartographer.
  4. Set PIN 1 on the DIP switch (WS3) on the Catalyst.K ToolHead to ON and PIN 2 to ON. This completes the hardware connections.

WARNING

  • the Catalyst.K ToolHead, Catalyst.K, and Cartographer all operate in USB mode.

RS-232 Communication Mode (Unsupported)

  1. Connect the RS-232 connector (XH2.54-4) on the main board (CATALYST.K) to the power connector (J1) on the tool board (Catalyst.K ToolHead)
  2. Connect the USB connector (USB4) on the main board (CATALYST.K) to the connector (J4) on the tool board (Catalyst.K ToolHead).
  3. Connect J23 on the tool board (Catalyst.K ToolHead) to the Cartographer.
  4. Set PIN 1 on the DIP switch (WS3) on the Catalyst.K ToolHead to OFF and PIN 2 to OFF. This completes the hardware connections.

WARNING

  • When the Catalyst.K ToolHead is operating in SERIAL mode, both Catalyst.K and Cartographer must operate in USB mode.
  • RS232 is a reserved feature and will be supported in future versions.

CAN Communication Mode

  1. Connect the RS-232 connector (XH2.54-4) on the main board (CATALYST.K) to the power terminal (J1) on the tool board (Catalyst.K ToolHead), and strip the white and green data wires from the cable harness to connect them to PIN 1 and PIN 2 of the CAN (XH2.54-3) connector on the main board (CATALYST.K), respectively.
  2. Connect J21 on the Catalyst.K ToolHead to the Cartographer.
  3. Set PIN 1 of the DIP switch (WS3) on the Catalyst.K ToolHead to OFF and PIN 2 to ON. This completes the hardware connections.

WARNING

  • the Catalyst.K ToolHead, Catalyst.K, and Cartographer all operate in CAN mode.

Header Jumpers

Fan2 , Fan3 can select the power supply voltage through the jumper cap.
As shown in the figure, the two pins on the left are connected together for 24V, and the two pins on the right are connected together for 5V.

NOTE

Please note that if these interfaces are used as outputs, the high-level voltage of the output is consistent with the voltage selected by the jumper. Please make sure that your peripherals can withstand the range. Generally speaking, only SSR in the accessories of 3D printers can withstand 9-36V control voltage.

Firmware Guide

Firmware Configuration

Klipper With No Bootloader (Recommend)

Warning

  • The host computer (such as a Raspberry Pi) must be connected to Wi-Fi or Ethernet. After obtaining the host computer's IP address using a LAN scanning tool such as Angry IP Scanner, you can then use an SSH tool to login to the host computer.

Login to the host computer using tool such as MobaXterm or PuTTY via SSH, and execute the following command to open the firmware configuration tool.

shell Copy 
cd ~/klipper
make menuconfig

The recommended mode is USB mode and the configuration is as follows.

USB (Recommend)

CAN

SERIAL (Unsupported)

Note

Serial communication is a reserved feature, support for it will be provided in future versions.

Complete the configuration shown in the reference image , then save the configuration and exit the configuration tool.

Note

If using Katapult, please refer to:
https://github.com/Arksine/katapult?tab=readme-ov-file#uploading-klipper

Firmware Upload

Waining

  • Before flashing the firmware, connect the Raspberry Pi and CATALYST.K using a USB cable，refer to the connection diagram USB Communication Mode (Recommend).
  • Before flashing the firmware, must complete the firmware configuration，refer to the Firmware Configuration
  • If the firmware is configured for CAN mode, please re-verify the wiring connections and DIP switch after the firmware flashing process is complete, refer to the connection diagram CAN Communication Mode.
  • If the firmware is configured for RS-232 mode, please re-verify the wiring connections and DIP switch after the firmware flashing process is complete, refer to the connection diagram RS-232 Communication Mode.

DFU mode

You need to enter DFU mode before you can compile and burn the firmware. As shown in the figure above,

  • press and hold BOOT0,
  • press the RESET button for one second,
  • release RESET,
  • wait for 3 seconds,
  • release BOOT0.

Use the command 'lsusb' to check if a DFU device is detected. If it appears, proceed with uploading the firmware. If not, repeat the previous steps.

Firmware flash

After the device is in DFU mode, execute the following commands to compile and flash the program.

shell Copy 
make flash FLASH_DEVICE=0483:df11

After the burning process is complete, it will display "File downloaded successfully".

Warning

  • The ID can only be recognized after the firmware flashing process is complete. If it has not yet finished, please refer to the Firmware Upload section.
  • If Mainsail or KlipperScreen indicates that it cannot connect to the MCU, you must modify the MCU ID before attempting to reconnect.

  • Open your browser, enter the IP address of the host computer in the address bar, for example, my host computer's IP is 192.168.0.179, just enter it and press Enter.

  • Open the web interface of the host computer, and find "Machine" in the configuration options on the left sidebar. Click to open the printer.cfg file.

  • Click the DEVICES button in the upper right corner.

Note

If DEVICES cannot be found, you need to reinstall Mainsail.

  • After selecting the communication method, click refresh. Copy the ID by clicking the arrow, then paste it into the [mcu ToolHead] section of printer.cfg.

  • Click the save and restart button in the upper right corner.

Attachments And Other Documents

2D，3D , SCH and config template file, please go to our github:
https://github.com/FYSETC/Catalyst.K_Kit

Where To Buy

www.fysetc.com

Technical Support Channel

support@fysetc.com
https://discord.gg/yYVx98gCDW

Last modified: 2026-03-18