BIG TREE TECH SKRat v1.0 User manual

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BIGTREETECH
SKRat v1.0
User Manual

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Contents
Revision History .............................................................5
Product Profile ...............................................................6
Feature Highlights........................................................6
Specifications............................................................7
Firmware ................................................................7
Dimensions ..............................................................8
Peripheral Port ...............................................................9
Connector Diagram.......................................................9
Pinout Diagram...........................................................9
Function Introduction........................................................10
LED Indicator Light ......................................................10
USB Power Supply ......................................................10
Downloading Firmware via DFU ..........................................11
To Choose the Working Mode of the TMC Driver ...........................11
STEP/DIR ...........................................................11
UART...............................................................12
SPI .................................................................13
Sensorless Homing..................................................13
Fan Voltage Selection....................................................14
+5V.................................................................14
12V.................................................................14
VIN .................................................................14
2-pin Fan Wiring.........................................................15
4-pin Fan Port Wiring ....................................................15
Proximity Switch ........................................................16
Voltage Selection....................................................16
PNP/NPN Type ......................................................16

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Proximity Switch Wiring .................................................17
Auto Power off (BIGTREETECH Relay V1.2) Wiring.........................17
Power Loss Recovery (BTT UPS 24V V1.0) Wiring..........................18
RGB Wiring .............................................................18
BLTouch Wiring .........................................................19
Filament Sensor Wiring ..................................................19
LCD Display Wiring......................................................20
SPI, I2C, UART ..........................................................20
100K NTC ...............................................................21
CAN bus Wiring .........................................................22
Marlin ......................................................................23
Install Compiling Environment ...........................................23
Download Marlin Firmware ...............................................23
Configure Firmware .....................................................23
Open Marlin Project .................................................23
Compiling Environment ..............................................23
Configure Motherboard and Serial Port ...............................24
Configure Stepper Driver.............................................25
Sensorless Homing..................................................25
100K NTC ...........................................................26
Max31865 ...........................................................26
BLTouch ............................................................27
Auto Power Off (Relay V1.2) ..........................................30
Power Loss Recovery................................................30
RGB ................................................................31
Filament Sensor.....................................................32
Smart Filament Sensor(SFS V1.0).....................................32
Compile Firmware .......................................................34

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Klipper .....................................................................35
Using Raspberry Pi ......................................................35
Download OS Image .................................................35
Download and Install Raspberry Pi Imager ............................35
Write Image .........................................................36
Using BIGTREETECH CB1 ...............................................39
Download OS Image .................................................39
Download and Install balenaEtcher ...................................39
Write OS ............................................................39
WiFi Setting.........................................................41
Configure the Motherboard...............................................42
SSH Connect to Device ..............................................42
Compile MCU Firmware ..............................................43
Firmware Update ....................................................44
Configure Klipper .......................................................46
Firmware Update ............................................................48
Cautions....................................................................48
FAQ ........................................................................48

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Revision History
Version
Note
Date
01.00
Original
2023/02/25

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Product Profile
BIGTREETECH SKRat v1.0 is a 3D printer motherboard jointly launched by
Shenzhen Big Tree Technology Co., Ltd. and Rat Rig.
Feature Highlights
32-bit 64 MHz ARM Cortex-M0+ series STM32G0B1VET6 MCU.
Onboard BOOT button to enable DFU mode to update the bootloader.
The thermistor circuit is protected to prevent MCU damage from shorted
heated bed and heater cartridge connection.
Four 2-pin fan ports, one always-on fan port, and two 4-pin fan ports.
All fans can realize VIN, 12V, 5V voltage selection via jumpers, and different
voltages can be set separately for different ports.
Integrated SPI and UART mode of TMC driver and DIAG pin, easily
configurable with jumpers.
Supports power loss recovery, filament runout sensor, auto power-off,
BLTouch, proximity switch, RGB, etc.
Onboard non-spring loaded microSD card slot for upgrading and configuring
firmware through microSD card, which is simple, convenient, and efficient.
Onboard CAN bus port.
The SPI expansion port is +3.3V and +5V selectable, which is convenient to
connect expansion modules, such as an ADXL345 accelerometer.
Onboard UART and I2C expansion output ports.

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Specifications
Dimensions
110 x 85mm, for details please refer to BTT
SKRat_V1.0_SIZE
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
4 x CNC, 1 x Always On, 2 x 4-pin Header
Fan Port Max. Current
1A Continuous, 1.5A Instantaneous
Overall Current
(Heater Cartridge +Drivers+All
Fans)
＜15A
Expansion Port
BLTouch (Servos, Probe), PS-ON, PWR-DET,
Fil-DET, RGB, CAN-FD, SPI, UART, I2C
Stepper Driver Mode
SPI, UART, STEP/DIR
Stepper Motor Socket
X, Y, Z (Dual Z axes), E0, E1 5 channels in total
Thermistor
5 x NTC Ports, 1 x PT100/PT1000
Display
2.4-inch TFT, 3.5-inch TFT, LCD12864 Screen...
PC Connection
Type-C
Supported File Format
G-code
Recommended Slicer/Console
Cura, Simplify3D, Pronterface, Repetier-host,
Makerware
Firmware
Supported Firmware: Marlin, Klipper

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Dimensions

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Peripheral Port
Connector Diagram
Pinout Diagram
For details please refer to BTT SKRat_V1.0_SIZE.

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Function Introduction
LED Indicator Light
After the motherboard is powered on:
Power-Red Light-Power Indicator: The solid red light indicates normal
motherboard power.
Status-Green Light-Status Indicator: When updating firmware, this light will flash
and then be controlled by the firmware.
D10-Green Light-HB (Heated Bed) Status Indicator: The light will remain solid
green when the heated bed is working and turn off when it is not.
D3, D6-Green Light-E0, E1 (Heater Cartridge) Status Indicator: The light will
remain solid green when the heater cartridge is working and turn off when it is
not.
FAN0, FAN1, FAN2, FAN3-Blue Light-CNC Fan Status Indicators: The blue lights
turn on when the corresponding CNC fan is running and turn off when the fan is
off.
MFAN-Blue Light-MFAN Status Indicator: The blue light will remain on when the
power supply is normal.
USB Power Supply
After the SKRat has been powered, the Power-Red Light on the middle of the
board will light up, indicating power on. If using USB to power the board, please
short the USB_5V with a jumper.

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Downloading Firmware via DFU
Press and hold the BOOT button, power on the motherboard, and the chip will enter the
DFU mode. At this time, you can connect the board to the PC via the Type-C port, and
update the firmware via DFU mode.
To Choose the Working Mode of the TMC Driver
STEP/DIR
e.g.: A4988, DRV8825, LV8729, ST820, etc., connect jumpers(MS0-MS2)
according to the microstep table below.

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Driver Chips
MS1
MS2
MS3
Microsteps
Excitation Mode
A4988
Max. 16
Microsteps
35V 2A
L
L
L
Full Step
2 Phase
H
L
L
1/2
1-2 Phase
L
H
L
1/4
W1-2 Phase
H
H
L
1/8
2W1-2 Phase
H
H
H
1/16
4W1-2 Phase
Current
𝐑𝑆=0.1Ω
𝐈𝐓𝐫𝐢𝐩𝐌𝐀𝐗 = 𝐕𝐑𝐄𝐅
𝟖 ∗ 𝐑𝑆
Driver Chips
MODE2
MODE1
MODE0
Microsteps
Excitation Mode
DRV8825
Max. 32
Microsteps
8.2V-45V 2.5A at
24V T=25℃
L
L
L
Full Step
2 Phase
L
L
H
1/2
1-2 Phase
L
H
L
1/4
W1-2 Phase
L
H
H
1/8
H
L
L
1/16
H
L
H
1/32
H
H
L
1/32
H
H
H
1/32
Current
𝐑𝐼𝑆𝐸𝑁𝑆𝐸=0.1Ω
𝐈𝐂𝐇𝐎𝐏 = 𝐕(𝐱𝐑𝐄𝐅)
𝟓 ∗ 𝐑𝐼𝑆𝐸𝑁𝑆𝐸
Driver Chips
MD3
MD2
MD1
Microsteps
Excitation Mode
LV8729
Max. 128
Microsteps
36V 1.8A
L
L
L
Full Step
2 Phase
L
L
H
1/2
1-2 Phase
L
H
L
1/4
W1-2 Phase
L
H
H
1/8
2W1-2 Phase
H
L
L
1/16
4W1-2 Phase
H
L
H
1/32
8W1-2 Phase
H
H
L
1/64
16W1-2 Phase
H
H
H
1/128
32W1-2 Phase
Current
RF1=0.22Ω
𝐈OUT = (𝐕𝐑𝐄𝐅 / 5 ) / RF1
Driver Chips
MS3
MS2
MS1
Microsteps
ST820
Max. 256
Microsteps
45V 1.5A
L
L
L
Full Step
L
L
H
1/2
L
H
L
1/4
L
H
H
1/8
H
L
L
1/16
H
L
H
1/32
H
H
L
1/128
H
H
H
1/256
Current
Rs=0.15Ω
𝐈𝐩𝐞𝐚𝐤 = 𝐕𝐑𝐄𝐅∗ 𝐕𝐃𝐃
𝟓 ∗ 𝐑𝐒
UART
e.g.: TMC2208, TMC2209, TMC2225, etc., place jumpers according to the
diagram below, microstep and current can be configured in firmware.

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SPI
e.g.: TMC2130, TMC5160, TMC5161, etc., place jumpers according to the
diagram below, microstep and current can be configured in firmware.
Sensorless Homing
When using sensorless homing, place jumpers according to the diagram below.
Note: The extra ENDSTOP cannot be used by selecting this function! ! !

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Fan Voltage Selection
+5V
Use a jumper cap to short the horizontal pins highlighted in the figure below.
12V
Use a jumper cap to short the horizontal pins highlighted in the figure below.
VIN
Use a jumper cap to short the horizontal pins highlighted in the figure below.
Note: Shorting the pins, as shown in the figure below, is strictly prohibited as it
may result in permanent damage to the motherboard.

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2-pin Fan Wiring
Onboard four 2-pin fan ports (FAN0,FAN1,FAN2,FAN3), one always on fan
port(MFAN).
4-pin Fan Port Wiring
Onboard two 4-pin fan ports: Four-Wire FAN0, Four-Wire FAN1
Note: Using a voltage that does not match a fan's rated working voltage can
cause abnormal fan operation or damage. Always ensure that the selected
voltage matches the fan's rated working voltage.

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Proximity Switch
Voltage Selection
Use a jumper cap to short the corresponding pin to choose +12V, +5V, VIN, as
shown in the figure below.
PNP/NPN Type
PNP Type: no need for a jumper cap.
NPN Type: place a jumper cap.
Note: Shorting the pins, as shown in the figure below, is strictly prohibited as it
may result in permanent damage to the motherboard.

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Proximity Switch Wiring
Auto Power off (BIGTREETECH Relay V1.2) Wiring

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Power Loss Recovery (BTT UPS 24V V1.0) Wiring
RGB Wiring

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BLTouch Wiring
Filament Sensor Wiring

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LCD Display Wiring
SPI, I2C, UART