BIGTREETECH SKR 2 - 32-bit Board with 5 Removable Drivers for Marlin, Klipper and RRF

The BIGTREETECH SKR 2 is a 32-bit controller board for DIY 3D printers, upgrades and rebuilds that require five removable driver channels, two hotend outputs, a heated bed and a broad range of displays, probes and sensors. Each socket can be configured for STEP/DIR, UART or SPI drivers, allowing the electronics to suit very different projects without locking the machine to one integrated driver type.

Architecture and capabilities

• MCU: the family was produced with the 168 MHz STM32F407VGT6 and 180 MHz STM32F429VGT6; firmware must match the actual chip.
• Power input: 12-24 V DC, 3.3 V logic.
• Drivers: five removable sockets for X, Y, Z, E0 and E1.
• Dual Z connector: ZAM and ZBM share the same Z driver; they can connect two motors in parallel but are not independent channels.
• Driver modes: STEP/DIR, UART and SPI through individual jumpers.
• Heating: two hotend outputs and one heated-bed output.
• Temperature: three analogue inputs, TH0, TH1 and TB, documented for 100 kOhm NTC thermistors.
• Fans: three PWM outputs and two direct-power fan connections.
• Storage: SDIO microSD and a USB-host connection, subject to the Wi-Fi/RRF selection.
• Expansion: EXP1/EXP2, serial TFT, probe, servo, PWR-DET, PS-ON, two filament/endstop inputs, RGB, I2C and ESP8266 Wi-Fi.

Technical specifications

Connectors and layout

The board groups motor outputs along the top edge, power and heaters on one side, and sensors, probe and power control along the lower section. This makes tidy wiring possible, but a connector label does not replace checking its pinout: reversed power, drivers, probes or endstops can damage the electronics.

Driver configuration

Configure each socket with the board fully powered off and the USB cable disconnected. STEP/DIR uses the driver's microstep jumpers; A4988 and DRV8825 also require RST and SLP to be linked in the position specified by BIGTREETECH. UART uses one communication jumper per axis, while SPI uses the corresponding four jumpers.

The DIAG jumper should only be installed on axes using sensorless homing with a compatible driver and matching firmware configuration. Remove DIAG when physical endstops are used unless the specific installation documentation states otherwise. Always check module orientation, maximum voltage, current and cooling; the StepStick form factor alone does not prove compatibility.

For a quiet UART setup it can be paired with the BIGTREETECH TMC2209 V1.3 driver, with jumpers, motor current and firmware configured for each motor.

Marlin

1. Read the MCU and PCB revision from the physical board. Do not select F407/F429 or Rev A/B from the shop name.
2. In current Marlin, a corrected Rev B board uses BOARD_BTT_SKR_V2_0_REV_B. The Rev A definition includes a safety warning and must not be bypassed without carrying out the required correction for that revision.
3. Select STM32F407VG_btt for F407 or STM32F429VG_btt for F429. Older repositories may show BIGTREE_SKR_2 and BIGTREE_SKR_2_F429.
4. Declare the actual drivers, sensors, extruders, endstops, display and printer geometry.
5. Compile, copy firmware.bin to a microSD card and restart the board, following the procedure for the Marlin version in use.

Klipper

Klipper provides an official SKR 2 template. Firmware is built for STM32F407 or STM32F429 with a 32 KiB bootloader, according to the actual chip. The template states that make flash does not work on this board: generate klipper.bin, rename it to firmware.bin and load it by microSD.

[output_pin motor_power]
pin: PC13
value: 1

This block is essential because it enables the safe power path for the drivers and most MOSFETs. The rest of printer.cfg must then be adapted to the printer. Do not copy the template's dimensions, thermistors, PID values, currents or motor directions as universal specifications. Klipper also needs an external Linux host and the board's real serial identifier.

RepRapFirmware

BIGTREETECH published RRF support for the SKR 2 using a compatible ESP8266 module. The jumper selection places Wi-Fi in SPI mode and disables USB mass storage; in USB-host mode, Wi-Fi is limited to UART and RRF cannot use that path. This is a legacy, revision-sensitive integration, so follow SKR 2-specific documentation rather than loading a generic image.

Driver anti-reversal protection was declared for Marlin, not RRF. With any firmware, install drivers with all power removed and double-check their orientation before the first power-up.

Displays, sensors and expansion

• EXP1/EXP2 can integrate graphical displays such as the BIGTREETECH MINI12864 V2.0, after checking cable orientation and firmware configuration.
• The serial TFT port can be used with the BIGTREETECH TFT35 V3.0; its touch and LCD modes use different connections and firmware settings.
• The detection inputs can be used with compatible devices such as the BIGTREETECH SFS V2.0, configuring presence and motion separately where applicable.
• BLTouch, servo probes, PWR-DET, PS-ON, RGB and I2C require the correct pinout, voltage and firmware; sharing a connector shape or wire count is not enough.

Dimensions and installation

The official drawing gives a PCB size of 109.67 x 84.30 mm, with 101.85 x 76.30 mm between the centres of the four mounting holes. Also allow for driver and heatsink height, microSD and USB access, and connector removal. Although the SKR 2 succeeded the SKR 1.4/Turbo, it should not be treated as a direct mechanical or electrical replacement without comparing enclosure, mounting points and wiring.

Safe installation

1. Check MCU, revision and applicable documentation before compiling or connecting drivers.
2. Set every jumper with the power supply and USB disconnected. Pay particular attention to logic power, driver mode, DIAG and Wi-Fi/U-disk selection.
3. Use suitable crimped terminals, observe polarity and size wire, fuses and power supply for each load.
4. Do not connect a bed drawing more than 10 A directly to the board. If external switching is required, use a correctly rated and protected solution.
5. Perform the first power-up without heaters or motors, verify 5 V/3.3 V and communications, then connect loads in stages.
6. Enable thermal protection and check every thermistor at room temperature before allowing any heater to energise.
7. Set driver current and cooling for the actual motors; do not reuse values from another machine without checking them.

Choose it if

• You need five removable drivers and want to choose between STEP/DIR, UART or SPI.
• You are building or upgrading a printer and can configure firmware, jumpers and wiring.
• You need two extruders, or one extruder and an additional axis, within the five available channels.
• You value microSD, USB host, several display options and expansion connectors on a compact board.

It is not for you if

• You want a plug-and-play replacement without compiling firmware or checking pinouts.
• You need more than five truly independent motor channels.
• You cannot identify the MCU and revision of an old or unknown-origin unit.
• You want to connect a bed exceeding the 10 A limit, or PT100/PT1000 sensors without an interface, directly to the board.

Technical documentation

The official BIGTREETECH SKR 2 repository contains the manual, pinout, schematic, dimensions and reference firmware. Use it together with current Marlin, Klipper or RepRapFirmware documentation and the physical revision of your board.