2 layers80 × 55 mm
Head
lachlanhurst/dukki
Bipedal robot based on Microduck, rebuilt around Unitree J288 servos and a Radxa CM4.
68 parts2MIT
2 layers45 × 80 mm
Bridge
lachlanhurst/dukki2Bipedal robot based on Microduck, rebuilt around Unitree J288 servos and a Radxa CM4.
- Size
- 45 × 80 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 72
- Nets
- 74
- Pads
- 220
- Tracks, vias
- 605, 187
- Pours
- 4
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 6 Sep 2026
- Updated
- 8 Nov 2026
Overview
Bridge is an open-source printed circuit board by lachlanhurst, from the lachlanhurst/dukki repository on GitHub, published under the MIT licence. It is a 2-layer board of 45 × 80 mm with 72 parts on 74 nets, routed with 605 tracks and 187 vias.
It is built around the LMR51606XDBVR-MS, BZT52C12S and 1N4148WS, with the B5819W, BAT54WS and BZT52C15 among its other parts. Its parts include 18 resistors, 15 capacitors, 10 connectors, 8 diodes and 6 fuses. It belongs with the robots and motor control and interfaces and adapters boards and the STM32 boards of this library.
Main components
10
LMR51606XDBVR-MS
SOT-23-6SOT-23-6 DC-DC Converters ROHSMSKSEMIDC-DC Converters
BZT52C12S
SOD-3231 Independent 100nA@8V 11.4V~12.7V 12V 150Ω 200mW 25Ω SOD-323 Zener Diodes ROHSJiangsu Changjing Electronics Technology (CJ)Zener Diodes1N4148WS
SOD-3231.25V@150mA 100V 150mA 1uA@75V 200mW 2A 4ns Independent SOD-323 Switching Diodes ROHSJiangsu Changjing Electronics Technology (CJ)Switching Diodes
B5819W
SOD-123-55℃~+125℃ 1.5A 1mA@40V 25A 40V 600mV@1A Standalone SOD-123 Schottky Diodes ROHSMDDSchottky DiodesBAT54WS
SOD-3231 Independent 100mA 1V@100mA 2uA@25V 30V 600mA SOD-323 Schottky Diodes ROHSDiodes IncorporatedSchottky DiodesBZT52C15
SOD-123-65℃~+150℃ 1 Independent 100nA@1V 13.8V~15.6V 15V 200Ω 30Ω 370mW SOD-123 Zener Diodes ROHSDiodes IncorporatedZener Diodes
MMBT3906
SOT-23-55℃~+150℃ 1 PNP 100 100nA 200mA 200mW 300MHz 300mV 40V 5V PNP SOT-23 Bipolar (BJT) ROHSTWGMCBipolar (BJT)
NCE40P70K
TO-252-2L-55℃~+150℃ 1 P-Channel 106nC@10V 10mΩ@10V 130W 2.5V 40V 70A P-Channel TO-252-2L MOSFETs ROHSWuxi NCE Power SemiconductorMOSFETs
SMBJ26A
DO-214AA(SMB)-65℃~+150℃ 14.3A 1uA 26V 31.9V 42.1V 600W@10/1000us TVS Unidirectional DO-214AA(SMB) ESD and Surge Protection (TVS/ESD) ROHSMDDESD And Surge Protection (TVS/ESD)
XT30U-M
-Male Plug、- Yellow - Power connector / plug connectorChangzhou Amass ElecPlug
README
README.mdDukki
[!IMPORTANT] Everything in here is very much a work in progress!
A rework of the Pollen Robotics Microduck with a few hardware changes:
- Radxa CM4 brain (instead of the Radxa Zero 3W)
- RK3576 vs RK3566: roughly twice the CPU and a 6 TOPS NPU vs 0.8 TOPS
- Unitree J288 servos (instead of the Dynamixel XL330-M288-T)
- About three times faster: 35 rad/s (25 V), vs about 11 rad/s for the XL330
- Twice the weight: 39 g vs 18 g
- Similar stall torque, about 0.45 N·m measured against 0.43 N·m for the XL330 model
Hardware block diagram
What's in this repository
This repository holds the Dukki documentation, the hardware design files (KiCad), and the code that doesn't fit neatly into one of the forked repos, such as the STM32 servo bridge firmware, compute module setup scripts and J288 bench test tools. Changes elsewhere live on branches of forked repos: the robot firmware in microduck (dukki), RL training in microduck_rl (dukki-j288), the J288 actuator model in bam (unitree-j288) and the head IMU driver in bmi088-rs (configurable-addresses).
Docs
Hardware is the main design document. It covers each subsystem (servos, compute, the STM32 servo bridge, IMUs, power, audio, camera, ToF) and compares it with the OG robot.
Compute setup takes a Radxa CM4 from the box to a board on WiFi at microduck.local. That includes flashing Armbian to the eMMC.
Servo setup is the bench procedure for each J288 before assembly. You set the bus ID with Unitree's Windows tool, record the firmware version, run a motion check and label the servo for its joint.
J288 bench testing has the results from characterising one servo: bus timing, friction, armature, torque limits and heating. The main finding is that peak output torque is about 0.45 N·m, close to the XL330.
Camera setup and audio setup bring up the IMX219 camera and the MAX98357A speaker and INMP441 microphone on the CM4.
Licence
MIT, see LICENSE. The third-party datasheets and schematics in docs/datasheets/ belong to their publishers and are not covered by it.
Parts
72| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | 2.2u 50V | Capacitor_SMD:C_0805_2012Metric | C1, C5, C6, C7, C8 |
| 4 | 0R | Resistor_SMD:R_0603_1608Metric | R5, R6, R7, R8 |
| 4 | 1M | Resistor_SMD:R_0603_1608Metric | R13, R15, R20, R22 |
| 4 | 4A | Fuse:Fuse_1206_3216Metric | F2, F3, F4, F5 |
| 4 | M2 | MountingHole:MountingHole_2.2mm_M2 | H1, H2, H3, H4 |
| 3 | 100n 50V | Capacitor_SMD:C_0603_1608Metric | C9, C10, C13 |
| 3 | 2N7002 | Package_TO_SOT_SMD:SOT-23 | Q2, Q3, Q5 |
| 2 | 100k | Resistor_SMD:R_0603_1608Metric | R11, R14 |
| 2 | 10k | Resistor_SMD:R_0603_1608Metric | R4, R12 |
| 2 | 10u 50V X7R | Capacitor_SMD:C_1210_3225Metric | C3, C4 |
| 2 | 1u 50V X7R | Capacitor_SMD:C_0805_2012Metric | C14, C15 |
| 2 | 22u 25V | Capacitor_SMD:C_0805_2012Metric | C11, C12 |
| 2 | 470k | Resistor_SMD:R_0603_1608Metric | R1, R2 |
| 2 | BZT52C12S | Diode_SMD:D_SOD-323 | D9, D13 |
| 1 | 10A | Fuse:Fuse_1206_3216Metric | F1 |
| 1 | 130k | Resistor_SMD:R_0603_1608Metric | R9 |
| 1 | 1N4148WS | Diode_SMD:D_SOD-323 | D12 |
| 1 | 1k | Resistor_SMD:R_0603_1608Metric | R3 |
| 1 | 2.2M | Resistor_SMD:R_0603_1608Metric | R21 |
| 1 | 22k | Resistor_SMD:R_0603_1608Metric | R10 |
| 1 | 2A | Fuse:Fuse_1206_3216Metric | F6 |
| 1 | 33u | Inductor_SMD:L_Sunlord_SWPA6045S | L1 |
| 1 | 47n 50V | Capacitor_SMD:C_0603_1608Metric | C2 |
| 1 | B5819W | Diode_SMD:D_SOD-123 | D8 |
| 1 | BAT54WS | Diode_SMD:D_SOD-323 | D11 |
| 1 | BZT52C15 | Diode_SMD:D_SOD-123 | D1 |
| 1 | Ext 5V | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | J9 |
| 1 | Head | Connector_JST:JST_PH_B4B-PH-K_1x04_P2.00mm_Vertical | J6 |
| 1 | LMR51606XDBVR | Package_TO_SOT_SMD:SOT-23-6 | U1 |
| 1 | LSM6DSV16X breakout | LSM6DSV16X_Breakout:LSM6DSV16X_Breakout | U3 |
| 1 | MMBT3906 | Package_TO_SOT_SMD:SOT-23 | Q4 |
| 1 | NCE40P70K | Package_TO_SOT_SMD:TO-252-2 | Q1 |
| 1 | OLED | Connector_JST:JST_PH_B5B-PH-K_1x05_P2.00mm_Vertical | J7 |
| 1 | PA5 breakout | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | J10 |
| 1 | Power button | Connector_JST:JST_PH_B2B-PH-K_1x02_P2.00mm_Vertical | J8 |
| 1 | SMBJ26A | Diode_SMD:D_SMB | D2 |
| 1 | Seg A | Connector_JST:JST_PH_B3B-PH-K_1x03_P2.00mm_Vertical | J2 |
| 1 | Seg B | Connector_JST:JST_PH_B3B-PH-K_1x03_P2.00mm_Vertical | J3 |
| 1 | Seg C | Connector_JST:JST_PH_B3B-PH-K_1x03_P2.00mm_Vertical | J4 |
| 1 | Seg D | Connector_JST:JST_PH_B3B-PH-K_1x03_P2.00mm_Vertical | J5 |
| 1 | WeAct STM32G474 QFN48 | WeAct_STM32G474CoreBoard:WeAct_STM32G474CoreBoard_QFN48 | U2 |
| 1 | XT30U-M | Connector_AMASS:AMASS_XT30U-M_1x02_P5.0mm_Vertical | J1 |
| 1 | bridge = always on | Jumper:SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm | JP2 |
| 1 | cut to isolate buck | Jumper:SolderJumper-2_P1.3mm_Bridged_RoundedPad1.0x1.5mm | JP1 |
| 1 | green | LED_SMD:LED_0603_1608Metric | D3 |
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Questions
How big is the Bridge PCB?
It measures 45 × 80 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Bridge use?
72 parts, built around the LMR51606XDBVR-MS, BZT52C12S, 1N4148WS and B5819W. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Bridge KiCad files?
From the lachlanhurst/dukki repository on GitHub, at the commit this page was made from: the board is hardware/bridge/bridge.kicad_pcb and its schematic hardware/bridge/bridge.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Bridge design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).