The BIGTREETECH SKRat v1.0 is a 3D printer motherboard developed by Shenzhen Big Tree Technology Co., Ltd. and Rat Rig. It is designed to offer a comprehensive and flexible solution for 3D printer control, supporting both Marlin and Klipper firmware.
Function Description:
The SKRat v1.0 serves as the central control unit for a 3D printer, managing various components such as stepper motors, heaters, fans, and sensors. It provides a robust platform for precise motion control, temperature regulation, and overall printer operation. The board is equipped with a 32-bit 64 MHz ARM Cortex-M0+ series STM32G0B1VET6 MCU, ensuring efficient processing and control.
Key functions include:
- Stepper Motor Control: Supports five stepper motor channels (X, Y, Z (Dual Z axes), E0, E1) with configurable SPI, UART, and STEP/DIR modes for various TMC drivers (e.g., A4988, DRV8825, LV8729, ST820, TMC2208, TMC2209, TMC2225, TMC2130, TMC5160, TMC5161). This allows for fine-tuning of microstepping and current settings via firmware. Sensorless homing is also supported for compatible drivers.
- Heating Control: Manages a heated bed (HB) and two heater cartridges (HE0, HE1). The thermistor circuit is protected to prevent MCU damage from shorted connections.
- Fan Control: Features four 2-pin CNC fan ports (FAN0, FAN1, FAN2, FAN3), one always-on fan port (MFAN), and two 4-pin fan ports (Four-Wire FAN0, Four-Wire FAN1). All fan ports offer VIN, 12V, or 5V voltage selection via jumpers, allowing for flexible fan configurations.
- Sensor Integration: Supports a wide range of sensors including 5 NTC thermistor ports, 1 PT100/PT1000 port (via MAX31865), BLTouch, proximity switches (PNP/NPN type with selectable +12V, +5V, VIN voltage), filament runout sensors (standard and Smart Filament Sensor SFS V1.0), and power loss detection.
- Expansion and Connectivity: Includes expansion ports for BLTouch (Servos, Probe), PS-ON, PWR-DET, Fil-DET, RGB, CAN-FD, SPI, UART, and I2C. The SPI expansion port is +3.3V and +5V selectable for connecting modules like ADXL345 accelerometers. Onboard CAN bus port and UART/I2C expansion output ports provide further connectivity options.
- Firmware Management: Features an onboard BOOT button for DFU mode to update the bootloader. Firmware can be upgraded and configured via a non-spring loaded microSD card slot, offering a simple and efficient process. A Type-C USB port is provided for PC connection.
- Display Support: Compatible with various displays such as 2.4-inch TFT, 3.5-inch TFT, and LCD12864 screens.
- Power Management: Supports auto power-off (with BIGTREETECH Relay V1.2) and power loss recovery (with BTT UPS 24V V1.0).
Important Technical Specifications:
- Dimensions: 110 x 85mm (Mounting Size: 110 x 85mm)
- MCU: ARM Cortex-M0+ STM32G0B1VET6
- Input Voltage: DC12V-DC24V
- Logic Voltage: DC 3.3V
- Heater Connection: Heated Bed (HB), Heater Cartridge (HE0, HE1)
- HB Port Max. Current: 10A Continuous, 15A Instantaneous
- Heater Cartridge Max. Current: 8A Continuous, 10A Instantaneous
- Fan Port Configuration: 4 x CNC (2-pin), 1 x Always On (2-pin), 2 x 4-pin Header
- Fan Port Max. Current: 1A Continuous, 1.5A Instantaneous
- Overall Current (Heater Cartridge + Drivers + All Fans): <15A
- Stepper Driver Mode: SPI, UART, STEP/DIR
- Stepper Motor Sockets: X, Y, Z (Dual Z axes), E0, E1 (5 channels total)
- Thermistor Ports: 5 x NTC Ports, 1 x PT100/PT1000
- PC Connection: Type-C
- Supported File Format: G-code
- Supported Firmware: Marlin, Klipper
Usage Features:
- Easy Configuration: Jumpers allow for straightforward selection of TMC driver working modes (STEP/DIR, UART, SPI), fan voltages (+5V, 12V, VIN), and proximity switch types (PNP/NPN).
- Firmware Update Flexibility: Firmware can be updated via DFU mode (using the BOOT button and Type-C USB) or by copying a
firmware.bin file to a microSD card. For Klipper, firmware compilation and flashing can be done via SSH.
- LED Indicators: Various LED lights provide visual feedback on the motherboard's status, including power (red), general status (green, flashing during firmware update), heated bed (green), heater cartridges (green), and CNC fans (blue).
- Power Loss Recovery: The board supports power loss recovery, either by saving print status to the microSD card after each layer (which can shorten card life) or by integrating with an external BTT UPS 24V V1.0 module for more robust recovery.
- Auto Power Off: Can be configured with a BIGTREETECH Relay V1.2 to automatically power off the printer.
- Sensorless Homing: For compatible TMC drivers, sensorless homing can be enabled by placing specific jumpers, eliminating the need for physical endstops.
- RGB Lighting: Supports RGB lighting, configurable via firmware, with options for different types (NEO_GRB) and number of LEDs.
- Klipper Integration: Detailed instructions are provided for setting up Klipper firmware, including downloading OS images for Raspberry Pi or BIGTREETECH CB1, installing the Raspberry Pi Imager or balenaEtcher, configuring WiFi, connecting via SSH, compiling MCU firmware, and configuring the
printer.cfg file.
Maintenance Features:
- Protected Thermistor Circuit: The thermistor circuit is designed with protection to prevent damage to the MCU from shorted heated bed or heater cartridge connections, enhancing the board's longevity.
- Firmware Update Process: The firmware update process is clearly outlined, including renaming the firmware file to
firmware.bin and ensuring the microSD card is formatted to FAT32. The board automatically renames firmware.bin to FIRMWARE.CUR upon successful update, providing a clear indication of completion.
- Voltage Selection for Fans: The ability to select fan voltages via jumpers helps prevent damage to fans by ensuring they operate at their rated voltage. Users are explicitly warned against shorting certain pins, as this can cause permanent damage.
- MicroSD Card Handling: Users are advised to be careful when inserting the microSD card, as the slot is not spring-loaded, to prevent damage.
- Current Limits: Clear specifications for maximum continuous and instantaneous currents for the heated bed, heater cartridges, and fan ports are provided, along with an overall current limit, to guide users in safe operation and component selection.
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