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🔥 Laser CANbus Toolhead PCB

🇩🇪 Deutsche Version: README.de.md

A compact, robust toolhead board for Klipper-based laser engravers and cutters (CoreXY). This board integrates power supply, laser driver logic, CAN-Bus communication, and input shaping (ICM-20602) in the smallest possible space.

Laser CANbus Toolhead PCB

📚 Contents

✨ Features

🧠 Microcontroller

  • MCU: STM32F072CBU6 (Cortex-M0, 48MHz, CAN-capable)
  • Stability: 12MHz crystal for maximum CAN-Bus stability
  • Firmware: Klipper-compatible

🔗 CAN-Bus Communication

  • Transceiver: SN65HVD230 with ESD protection
  • Termination: Split termination via solder jumper
  • Slope Control: Switchable for EMI optimization

📊 Input Shaping

  • Sensor: On-board ICM-20602 accelerometer/gyroscope (SPI)
  • Purpose: Klipper resonance measurement for perfect print quality
  • Advantage: Better availability and modern sensor technology

⚡ Laser Power Control

  • Circuit: 24V / 6A High-Side Switch (CJAC70P06 P-MOSFET, 60V rated)
  • Peak Current: 8A capability
  • Soft-Start: Limits inrush current (Rise-time ~1.2ms)
  • Safety: Hardware pull-down prevents unwanted activation
  • Limitation: Max 6A limited by Micro Fit 3.0 connector with 0.75mm² wire

🎛️ Laser Signal Control

  • PWM: 5V Level-shifted via 74AHCT1G125 buffer
  • Quality: Clean edges, true hardware PWM via STM32 timer
  • Compatibility: Common diode lasers

🔌 Power Supply

  • Input: 24V with 250mA PTC fuse and SMF24A TVS diode
  • 5V Rail: MP2459 Buck converter (up to 60V input tolerant)
  • 3.3V Rail: XC6206 LDO for MCU and peripherals

🚨 Diagnostics & Monitoring

  • Power LEDs: 24V In, 24V Sys, 5V, 3.3V
  • Status LEDs: Laser Enable, Laser PWM, Heartbeat

📋 Klipper Configuration

Basic MCU Setup

[mcu toolhead]
canbus_uuid: <your-uuid>  # Find with "ls /dev/serial/by-id/*" or "~/klippy-env/bin/python ~/klipper/scripts/canbus_query.py can0"

[temperature_sensor toolhead_mcu]
sensor_type: temperature_mcu
sensor_mcu: toolhead

Input Shaping (ICM-20602)

[mpu9250]
cs_pin: toolhead:PA4
spi_bus: spi1
#axes_map: x,y,z  # Configure according to your printer orientation

[resonance_tester]
accel_chip: mpu9250
probe_points:
    150, 150, 20  # Adjust to your bed size

Laser Control

# Laser PWM Signal
[output_pin laser_pwm]
pin: toolhead:PB14
pwm: True
cycle_time: 0.001          # 1kHz PWM frequency
shutdown_value: 0          # Safety: laser off during emergency

# Laser Enable (optional)
[output_pin laser_enable]
pin: toolhead:PB15
value: 0
shutdown_value: 0

# Heartbeat LED (optional)
[output_pin heartbeat]
pin: toolhead:PA9
pwm: True
cycle_time: 1.0

🔌 Pinout & Connector Assignment

J101 - Power & CAN Input (Micro-Fit 3.0, 2x2, THT)

Pin Signal Description
1 +24V Main power input (High Current)
2 GND Ground
3 CAN_H CAN-Bus High Signal
4 CAN_L CAN-Bus Low Signal

J102 - Laser Output (Micro-Fit 3.0, 1x3, THT)

Pin Signal Description
1 GND Laser Ground
2 PWM 5V PWM Signal (Level-Shifted)
3 +24V Switched Laser Power (Soft-Start)

Debug/Programming Header (Back Side)

Pad Pin Signal Function
1 - 5V 5V Supply (from Programmer)
2 - 3.3V VTref (Reference Voltage)
3 PA13 SWDIO Serial Wire Debug I/O
4 PA14 SWCLK Serial Wire Debug Clock
5 - NRST Reset Signal
6 - GND Ground

💡 Bootloader Mode: To force the STM32 into DFU/Bootloader mode (e.g., for initial flash with Katapult), bridge the BOOT0 pad with 3.3V during power-on.

🔧 Installation & Setup

1. CAN-Bus Configuration

  • Set CAN-Bus termination according to position in network
  • Baud rate: 1 Mbit/s (Klipper standard)

2. Firmware Flash

  1. Put board into DFU mode (bridge BOOT0)
  2. Compile Klipper for STM32F072 with CAN support
  3. Flash firmware: make flash FLASH_DEVICE=<dfu-device>

3. Find UUID

~/klippy-env/bin/python ~/klipper/scripts/canbus_query.py can0

⚠️ Safety Notes

  • Laser Safety: Always wear protective eyewear
  • Power Supply: Only operate with 24V DC
  • Initial Setup: Slowly ramp up laser power
  • Emergency: Hardware pull-down ensures safe state

🛠️ BOM (Bill of Materials) - Highlights

Component Value/Type Function Package Order Code
U101 STM32F072CBU6 Main Microcontroller UFQFPN-48 STM32F072CBU6
U102 MP2459GJ-Z Buck Converter 24V→5V TSOT-23-8 MP2459GJ-Z
U105 SN65HVD230DR CAN-Bus Transceiver SOIC-8 SN65HVD230DR
U106 ICM-20602 6-Axis IMU (Accelerometer/Gyroscope) LGA-16 ICM-20602
Q101 CJAC70P06 P-MOSFET (Laser Switch, 60V) SOIC-8 CJAC70P06
D101 SMF24A TVS Diode (Overvoltage Protection) DO-214AC SMF24A
F101 1812L025 PTC Fuse 250mA 1812 1812L025
Y101 12MHz Crystal for CAN Stability HC-49/S 12MHz Crystal
J101/J102 Micro-Fit 3.0 THT Connectors THT Micro-Fit 3.0 THT

🛠️ Technical Specifications

Parameter Value Unit
Input Voltage 24 ± 2 V
Laser Current (max) 4 A
CAN Baud Rate 1 Mbit/s
PWM Frequency 1 kHz
Soft-Start Time ~1.2 ms
Operating Temperature -10 to +70 °C
Dimensions TBD mm

📝 Changelog

Rev. 1

  • Transistor Upgrade: Replaced MOSFET with CJAC70P06 (60V voltage rating)
  • Sensor Upgrade: Changed from ADXL345 to ICM-20602 (better availability, modern 6-axis IMU)
  • Connector Change: Micro Fit 3.0 connectors changed from SMD to THT mounting
  • Silkscreen Enhancement: Added connector pin assignments to silkscreen for easier assembly
  • Layout Improvements: Cleaned up component placement and optimized routing
  • Documentation: Updated overview image to reflect current design
  • BOM Update: Added component order numbers and updated production data
  • Production Files: Updated assembly and production files with current components

Rev. 0 (Initial Release)

  • Initial PCB design with STM32F072CBU6 microcontroller
  • CAN-Bus communication with SN65HVD230 transceiver
  • 24V/4A laser power control with AO4407A MOSFET
  • ADXL345 accelerometer for input shaping
  • MP2459 buck converter for power supply

📚 Additional Resources