🔥 Laser CANbus Toolhead PCB

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 (ADXL345) in the smallest possible space.

✨ 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 ADXL345 accelerometer (SPI)
• Purpose: Klipper resonance measurement for perfect print quality

⚡ Laser Power Control

• Circuit: 24V / 4A High-Side Switch (AO4407A P-MOSFET)
• Soft-Start: Limits inrush current (Rise-time ~1.2ms)
• Safety: Hardware pull-down prevents unwanted activation

🎛️ 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 (ADXL345)

[adxl345]
cs_pin: toolhead:PA4
spi_bus: spi1
axes_map: x,y,z

[resonance_tester]
accel_chip: adxl345
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)

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)

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
U101	STM32F072CBU6	Main Microcontroller	UFQFPN-48
U102	MP2459GJ-Z	Buck Converter 24V→5V	TSOT-23-8
U105	SN65HVD230DR	CAN-Bus Transceiver	SOIC-8
U106	ADXL343/ADXL345	3-Axis Accelerometer	LGA-14
Q101	AO4407A	P-MOSFET (Laser Switch)	SOIC-8
D101	SMF24A	TVS Diode (Overvoltage Protection)	DO-214AC
F101	1812L025	PTC Fuse 250mA	1812
Y101	12MHz	Crystal for CAN Stability	HC-49/S

🛠️ 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

📚 Additional Resources

• Klipper Documentation
• CAN-Bus Setup Guide
• Input Shaping
• Katapult Firmware Flasher

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🇩🇪 Deutsche Version: Readme.de.md