Microduck

Microduck 是一个小型双足机器人项目，包含两部分：

• microduck/: Raspberry Pi Zero 2 W 上运行的部署代码，负责读取 IMU、读取手柄/键盘输入、驱动 Dynamixel 舵机，并加载 ONNX 行走策略。
• mjlab_microduck/: 基于 MuJoCo/MjLab 的强化学习训练环境，用来训练并导出 walk.onnx。

本 README 面向装机和第一次运行：准备硬件、接线、刷写 microduck.img.xz、初始化 Wi-Fi、SSH 登录、运行模型，以及后续更新代码。3D打印的文件在项目中。

视频教程：https://www.youtube.com/watch?v=Vep8AjoCnEM

致谢

感谢开源项目 microban 和 microduck。本项目的机械结构、部署思路、仿真训练和实机行走流程都受益于这些开源工作。

项目状态

当前发布镜像已经内置：

• Raspberry Pi OS Lite 64-bit。
• 主机名 microduck。
• 默认用户 user。
• 部署目录 ~/microduck。
• Python 虚拟环境 ~/microduck/.venv。
• 行走模型 ~/microduck/src/agents/walk.onnx。
• 无头手柄服务 microduck-gamepad.service，可开机后用手柄启动模型。

当前预构建镜像：

• microduck.img.xz

BOM

下面是组装一台 Microduck 的主要物料。价格会随地区、采购渠道和批量变化，仅用于估算。

舵机 ID

控制代码期望的 ID 映射如下。烧录镜像之前或第一次运行之前，应先用 Dynamixel Wizard 设置好每个舵机。

Dynamixel Wizard 推荐参数：

• Protocol: 2.0
• Baud Rate: 1Mbps
• Return Delay Time: 0
• PWM Slope: 255
• Shutdown: 去掉输入电压错误触发项，避免电池电压波动时误停

接线图

电源接线

电源链路如下：

flowchart LR
    BAT[成品 6V 可充电电池] --> SW[电源开关]
    SW --> OPENRB[OpenRB-150 电源输入]
    OPENRB --> BUS[XL330 舵机总线]
    PI[Raspberry Pi Zero 2 W] -->|USB 数据线| OPENRB
    BAT --> REG[5V 稳压/USB 供电]
    REG --> PI

检查要点：

• 上电前用万用表确认正负极。
• 当前硬件使用成品 6V 可充电电池，不需要自制 2S 电池组、BMS 和 2S 充电板。
• OpenRB-150 负责 XL330 舵机通信，Raspberry Pi 通过 USB 连接 OpenRB-150。
• Raspberry Pi 需要稳定 5V 供电；舵机/OpenRB-150 使用 6V 电池侧供电。两侧必须共地，具体以你的电源模块和 OpenRB-150 接法为准。
• 焊点需要热缩管或热熔胶绝缘，避免短路。

舵机总线

XL330 使用 3-pin 串联总线。OpenRB-150 接出后可通过分线分到左右腿和头部。

flowchart TD
    OPENRB[OpenRB-150 Dynamixel Port]
    OPENRB --> SPLIT[分线]
    SPLIT --> R5[右腿链: ID 5 -> 4 -> 3 -> 2 -> 1]
    SPLIT --> L10[左腿链: ID 10 -> 9 -> 8 -> 7 -> 6]
    SPLIT --> H12[头颈链: ID 12 -> 11 -> 13 -> 14]

注意：

• 舵机顺序可以按结构方便布线，但 ID 必须和上表一致。
• 如果总线上有通信错误，优先检查 OpenRB-150 是否枚举成功、电池电压、GND、线序和舵机 ID。
• 正常情况下代码会自动选择 OpenRB-150 的 USB 串口；如果没有找到，会回退到 /dev/ttyACM0、/dev/serial0、/dev/ttyAMA0 或 /dev/ttyS0。

IMU 接线

BNO08x 模块走 I2C：

软件默认使用 I2C bus 1，会自动寻找 BNO08x 常见地址。安装方向由 IMU_MOUNT_QUAT 配置，已经和当前行走模型匹配。

使用 microduck.img.xz

1. 校验镜像

下载或拷贝镜像后，建议先校验：

sha256sum microduck.img.xz

应与发布页面或上文给出的 SHA256 一致。

2. 刷写 SD 卡

推荐使用 Raspberry Pi Imager：

1. 插入 microSD 卡。
2. 打开 Raspberry Pi Imager。
3. Choose Device 选择 Raspberry Pi Zero 2 W。
4. Choose OS 选择 Use custom，选中 microduck.img.xz。
5. Choose Storage 选择目标 microSD 卡。
6. 如果提示是否应用 OS customization，选择 No。
7. 点击 Write，等待写入和验证完成。

Linux 命令行也可以刷写，但要非常确认设备名：

lsblk
xzcat microduck.img.xz | sudo dd of=/dev/sdX bs=4M status=progress conv=fsync

把 /dev/sdX 换成你的 SD 卡设备，不要写成电脑硬盘。

3. 初始化 Wi-Fi

两种方法任选其一。Pi Zero 2 W 只支持 2.4GHz Wi-Fi，不要使用纯 5GHz 网络。

方法 1：在电脑上编辑 SD 卡

刷写完成后，拔下再插回 SD 卡。Ubuntu 通常会挂载出两个分区：

• bootfs: 启动分区，可直接编辑 Wi-Fi 配置。
• rootfs: 系统根分区，一般不需要手动改。

编辑：

sudo nano /media/$USER/bootfs/network-config

内容类似：

network:
  version: 2
  ethernets:
    eth0:
      dhcp4: true
      dhcp6: true
      optional: true
  wifis:
    wlan0:
      dhcp4: true
      regulatory-domain: "<YOUR_COUNTRY_CODE>"
      access-points:
        "<YOUR_WIFI_NAME>":
          password: "<YOUR_WIFI_PASSWORD>"
      optional: true

把三处占位符改掉：

• <YOUR_COUNTRY_CODE>: 两位国家/地区代码，例如 CN、US、GB、FR。
• <YOUR_WIFI_NAME>: Wi-Fi 名称。
• <YOUR_WIFI_PASSWORD>: Wi-Fi 密码。

可配置多个 Wi-Fi：

      access-points:
        "HomeWifi":
          password: "home-password"
        "PhoneHotspot":
          password: "hotspot-password"

保存后安全弹出 SD 卡，插入机器人，打开电源。

方法 2：插上 HDMI 和键盘，在 Pi 上用 nmcli

刷写完成后把 SD 卡插入 Pi，接上 mini HDMI 显示器和 USB 键盘（Zero 需要 OTG 转接头）。镜像是 Raspberry Pi OS Lite，没有桌面，开机后是终端登录。

第一次启动会扩展分区，等待 1 到 3 分钟，不要断电。出现登录提示后：

用户名: user
密码:   password

输入密码时屏幕不会显示字符，直接回车。然后扫描并连接 Wi-Fi，设为开机自动连接：

nmcli device wifi list
sudo nmcli device wifi connect "你的WiFi名字" password "你的WiFi密码"
sudo nmcli con mod "你的WiFi名字" wifi.powersave disable
sudo nmcli con mod "你的WiFi名字" connection.autoconnect yes

检查是否连上、是否自动连接：

nmcli -t -f NAME,TYPE,AUTOCONNECT,DEVICE connection show
hostname -I

AUTOCONNECT 应为 yes，并且已经拿到 IP。之后每次开机都会自动连这个 Wi-Fi。

首次启动

第一次启动会做几件事：

• 扩展文件系统到整张 SD 卡。
• 重新生成 SSH host keys。
• 读取 network-config 并连接 Wi-Fi（方法 1）。若用方法 2，首次启动后再用 nmcli 配置。
• 启动后台手柄服务。

等待 1 到 3 分钟，然后在电脑上测试：

ping microduck.local

如果 .local 解析失败，到路由器后台查看 Pi 的 IP，然后用 IP 登录。

默认登录：

ssh user@microduck.local

默认密码：

password

第一次登录后建议立刻改密码：

passwd

第一次运行模型

SSH 模式

在电脑上远程登录 Pi。Windows 用 PowerShell，Linux / macOS 用终端：

ssh user@microduck.local

默认密码是 password。如果提示 REMOTE HOST IDENTIFICATION HAS CHANGED，先清掉旧记录再重连：

ssh-keygen -R microduck.local

登录成功后，把机器人放在稳定平面上或扶住，然后启动控制程序：

cd ~/microduck
PYTHONPATH=src .venv/bin/python src/main.py

启动后程序会：

1. 打开舵机扭矩。
2. 平滑回到 neutral pose。
3. 读取键盘或手柄输入。
4. 加载 src/agents/walk.onnx 行走策略。

键盘控制：

远程 SSH 运行

电脑和机器人连同一个 2.4GHz Wi-Fi 后，在 Windows PowerShell 或 Linux / macOS 终端执行：

ssh user@microduck.local

登录后：

cd ~/microduck
PYTHONPATH=src .venv/bin/python src/main.py

停止：按 q。如果程序还在跑，另开一个 SSH 窗口：

ssh user@microduck.local
cd ~/microduck
PYTHONPATH=src .venv/bin/python src/stop.py

安全关机：

ssh user@microduck.local
sudo shutdown -h now

不要直接断电。先关机，等 10 到 15 秒，再关闭电源开关。

手柄模式

配对蓝牙手柄

SSH 到 Pi 后：

bluetoothctl

在 bluetoothctl 里执行：

power on
agent on
scan on
pair XX:XX:XX:XX:XX:XX
trust XX:XX:XX:XX:XX:XX
connect XX:XX:XX:XX:XX:XX
scan off
quit

把 XX:XX:XX:XX:XX:XX 换成扫描到的手柄 MAC 地址。

无头运行

镜像里已经启用无头手柄服务。开机后：

手柄连接时，服务会关闭 Wi-Fi 以改善 2.4GHz 蓝牙稳定性。需要 SSH 时，先关闭手柄，Wi-Fi 会自动恢复。

常用命令

在开发电脑的 microduck/ 目录下：

更新模型

训练仓 mjlab_microduck/ 导出的 ONNX 模型应放到：

microduck/src/agents/walk.onnx

更新后同步：

cd microduck
make sync

下一次运行会加载新的 walk.onnx。

重新制作发布镜像

当 Pi 上的系统、依赖、服务和模型都确认可用后，可以把这张 SD 卡做成新的 microduck.img.xz。

推荐流程：

1. 先用当前 SD 卡实机测试 make run 或手柄无头运行。
2. 关机，把 SD 卡插回电脑。
3. 克隆整张卡到本地 .img 文件。
4. 只在镜像副本里清理敏感信息：
   • Wi-Fi 配置。
   • SSH host keys。
   • 用户 SSH key。
   • /etc/machine-id。
   • cloud-init 状态。
   • shell history、日志、apt 缓存。
5. 重置 bootfs/network-config 为占位模板。
6. 确认 ~/microduck/src/agents/walk.onnx、.venv、microduck-gamepad.service 都存在。
7. 用 PiShrink 压缩生成 microduck.img.xz。
8. 计算 SHA256，并把校验值记录到 README 或 Release 说明里。

本仓库已有详细步骤：

microduck/docs/dev/clone_sd.md

目录结构

.
├── README.md
├── microduck/
│   ├── Makefile
│   ├── src/
│   │   ├── main.py
│   │   ├── scheduler.py
│   │   ├── robot_controller.py
│   │   ├── imu_reader.py
│   │   ├── agents/walk.onnx
│   │   └── moves/walk.py
│   ├── systemd/
│   └── docs/
└── mjlab_microduck/
    ├── src/mjlab_microduck/
    └── logs/

故障排查

找不到 microduck.local

先等 1 到 3 分钟。仍找不到时：

• 确认 Wi-Fi 是 2.4GHz。
• 确认 network-config YAML 缩进没变（方法 1）。
• 若用方法 2，在 Pi 上执行 nmcli device wifi list 和 hostname -I 确认已连上 2.4GHz 并拿到 IP。
• 到路由器后台查 Pi 的 IP。
• 用 ssh user@<IP> 登录。

SSH 提示 host key changed

发布镜像首次启动会重新生成 SSH host keys。如果同一台电脑以前连过另一张卡，清理本机记录：

ssh-keygen -R microduck.local
ssh-keygen -R <IP>

舵机不动或通信错误

检查：

• 电池电压是否正常。
• OpenRB-150、舵机总线和 Raspberry Pi 供电/GND 是否正确。
• 舵机 ID 是否符合上表。
• Dynamixel 波特率是否为 1Mbps。
• OpenRB-150 的 USB 串口是否能被识别。
• 线序、分线和插头方向是否正确。

手柄连接后 SSH 断开

这是无头模式的设计：手柄连接后会关闭 Wi-Fi，提升蓝牙稳定性。关闭手柄后 Wi-Fi 会恢复。

机器人一启动就容易倒

先手扶机器人运行，确认：

• 左右腿舵机 ID 没有装反。
• 膝盖 offset 与实际装配一致。
• IMU 安装方向正确。
• walk.onnx 是当前硬件对应的模型。

安全提示

• 第一次运行一定要扶住机器人。
• 不要在桌边或高处测试。
• 不要在电池低电压时长时间运行。
• 不要直接断电，先执行 make shutdown 或手柄安全关机。
• 充电和上电前检查短路、极性和焊点绝缘。

Microduck (English)

Microduck is a compact biped robot project. This repository presents one practical hardware and software setup for running an ONNX reinforcement learning walking policy on real Dynamixel XL330 servos.

The project contains two main parts:

• microduck/: deployment code for the Raspberry Pi Zero 2 W. It reads the IMU, reads keyboard or gamepad commands, drives Dynamixel servos, and loads the ONNX walking policy.
• mjlab_microduck/: reinforcement learning training environment based on MuJoCo/MjLab. It is used to train and export walk.onnx.

This README covers the full first-time workflow: hardware, wiring, flashing microduck.img.xz, Wi-Fi setup, first SSH login, first run, day-to-day usage, and rebuilding a release image.

Acknowledgements

Thanks to the open-source projects microban and microduck. This project benefits from their mechanical design, deployment ideas, simulation training work, and real-robot walking pipeline.

Project Status

The current release image includes:

• Raspberry Pi OS Lite 64-bit.
• Hostname microduck.
• Default user user.
• Deployment directory ~/microduck.
• Python virtual environment ~/microduck/.venv.
• Walking model ~/microduck/src/agents/walk.onnx.
• Headless gamepad service microduck-gamepad.service, so the walking controller can be started from a gamepad after boot.

Current prebuilt image:

• microduck.img.xz

SHA256:

096885dc32fb5b1db2ad69ba6bea868d8ab988f2b47c0d884eb63ba0dfdcb5c4

BOM

The following is the main bill of materials for building one Microduck. Prices vary by region, supplier, and quantity, so treat them as estimates.

Recommended extras:

• Spare XL330 servos, spare 6V battery, power wires, and Dynamixel cables.
• JST-EH terminals, crimping tool, heat-shrink tubing, and hot glue.
• A multimeter for checking polarity and battery voltage.

Servo IDs

The deployment code expects the following ID mapping. Configure every servo with Dynamixel Wizard before the first run.

Recommended Dynamixel Wizard settings:

• Protocol: 2.0
• Baud Rate: 1Mbps
• Return Delay Time: 0
• PWM Slope: 255
• Shutdown: remove the input-voltage-error trigger to avoid unwanted shutdowns during battery voltage dips

Wiring

Power Wiring

The power path is:

flowchart LR
    BAT[Ready-made 6V rechargeable battery] --> SW[Power switch]
    SW --> OPENRB[OpenRB-150 power input]
    OPENRB --> BUS[XL330 servo bus]
    PI[Raspberry Pi Zero 2 W] -->|USB data cable| OPENRB
    BAT --> REG[5V regulator / USB power]
    REG --> PI

Checklist:

• Check polarity with a multimeter before powering on.
• This setup uses a ready-made 6V rechargeable battery. It does not require a custom two-cell battery pack, BMS, or 2S charger board.
• OpenRB-150 handles XL330 servo communication. The Raspberry Pi connects to it over USB.
• The Raspberry Pi needs stable 5V power. The servos/OpenRB-150 are powered from the 6V battery side. Grounds must be common. Follow your actual regulator and OpenRB-150 wiring.
• Insulate solder joints with heat-shrink tubing or hot glue to prevent shorts.

Servo Bus

XL330 servos use a 3-pin daisy-chain bus. The OpenRB-150 output can be split into the right leg, left leg, and head/neck chains.

flowchart TD
    OPENRB[OpenRB-150 Dynamixel Port]
    OPENRB --> SPLIT[Splitter]
    SPLIT --> R5[Right leg chain: ID 5 -> 4 -> 3 -> 2 -> 1]
    SPLIT --> L10[Left leg chain: ID 10 -> 9 -> 8 -> 7 -> 6]
    SPLIT --> H12[Head/neck chain: ID 12 -> 11 -> 13 -> 14]

Notes:

• The physical cable order can follow the mechanical layout, but the servo IDs must match the table above.
• If the bus has communication errors, first check that the OpenRB-150 enumerates correctly, then check battery voltage, ground, cable order, and servo IDs.
• Normally the code automatically selects the OpenRB-150 USB serial port. If not found, it falls back to /dev/ttyACM0, /dev/serial0, /dev/ttyAMA0, or /dev/ttyS0.

IMU Wiring

The BNO08x module uses I2C:

The software uses I2C bus 1 by default and auto-detects common BNO08x addresses. The mounting orientation is configured by IMU_MOUNT_QUAT, which is already matched to the current walking model.

Using microduck.img.xz

1. Verify the Image

After downloading or copying the image, verify it:

sha256sum microduck.img.xz

The result should match the SHA256 published with the image.

2. Flash the SD Card

Raspberry Pi Imager is recommended:

1. Insert the microSD card.
2. Open Raspberry Pi Imager.
3. Select Choose Device -> Raspberry Pi Zero 2 W.
4. Select Choose OS -> Use custom, then choose microduck.img.xz.
5. Select Choose Storage, then choose the target microSD card.
6. If asked whether to apply OS customization settings, choose No.
7. Click Write and wait for writing and verification to complete.

You can also flash from the Linux command line. Be very careful with the device name:

lsblk
xzcat microduck.img.xz | sudo dd of=/dev/sdX bs=4M status=progress conv=fsync

Replace /dev/sdX with your SD card device. Do not write to your computer's internal disk.

3. Initialize Wi-Fi

Use either method. The Raspberry Pi Zero 2 W only supports 2.4GHz Wi-Fi. Do not use a 5GHz-only network.

Method 1: Edit the SD card on a computer

After flashing, unplug and reinsert the SD card. Ubuntu usually mounts two partitions:

• bootfs: boot partition, where Wi-Fi can be configured.
• rootfs: root filesystem, usually no manual edits are needed.

Edit:

sudo nano /media/$USER/bootfs/network-config

The file looks like this:

network:
  version: 2
  ethernets:
    eth0:
      dhcp4: true
      dhcp6: true
      optional: true
  wifis:
    wlan0:
      dhcp4: true
      regulatory-domain: "<YOUR_COUNTRY_CODE>"
      access-points:
        "<YOUR_WIFI_NAME>":
          password: "<YOUR_WIFI_PASSWORD>"
      optional: true

Replace:

• <YOUR_COUNTRY_CODE>: two-letter country code, such as CN, US, GB, or FR.
• <YOUR_WIFI_NAME>: Wi-Fi name.
• <YOUR_WIFI_PASSWORD>: Wi-Fi password.

Multiple Wi-Fi networks can be configured:

      access-points:
        "HomeWifi":
          password: "home-password"
        "PhoneHotspot":
          password: "hotspot-password"

Save the file, safely eject the SD card, insert it into the robot, and power on.

Method 2: HDMI and keyboard, then nmcli on the Pi

After flashing, insert the SD card into the Pi and connect a mini HDMI display plus a USB keyboard (the Zero needs a USB OTG adapter). The image is Raspberry Pi OS Lite, so there is no desktop — only a terminal login.

The first boot expands the partition. Wait 1 to 3 minutes and do not power off. When the login prompt appears:

username: user
password: password

The password is not echoed. Then scan, connect, and enable autoconnect:

nmcli device wifi list
sudo nmcli device wifi connect "YOUR_WIFI_NAME" password "YOUR_WIFI_PASSWORD"
sudo nmcli con mod "YOUR_WIFI_NAME" wifi.powersave disable
sudo nmcli con mod "YOUR_WIFI_NAME" connection.autoconnect yes

Check that it is connected and set to autoconnect:

nmcli -t -f NAME,TYPE,AUTOCONNECT,DEVICE connection show
hostname -I

AUTOCONNECT should be yes, and the Pi should have an IP address. After that, this Wi-Fi will connect automatically on every boot.

First Boot

On first boot, the image will:

• Expand the filesystem to the full SD card.
• Regenerate SSH host keys.
• Read network-config and join Wi-Fi (method 1). If you use method 2, configure Wi-Fi with nmcli after the first boot.
• Start the background gamepad service.

Wait 1 to 3 minutes, then test from your computer:

ping microduck.local

If .local does not resolve, check your router's DHCP client list and use the Pi's IP address.

Default login:

ssh user@microduck.local

Default password:

password

Change the password after the first login:

passwd

First Run

SSH Mode

Log in to the Pi from a computer. Use PowerShell on Windows, or a terminal on Linux / macOS:

ssh user@microduck.local

The default password is password. If SSH says REMOTE HOST IDENTIFICATION HAS CHANGED, clear the old host key and try again:

ssh-keygen -R microduck.local

After login, place the robot on a stable surface or hold it, then start the control program:

cd ~/microduck
PYTHONPATH=src .venv/bin/python src/main.py

On startup, the program will:

1. Enable servo torque.
2. Smoothly move to the neutral pose.
3. Read keyboard or gamepad input.
4. Load src/agents/walk.onnx.

Keyboard controls:

Remote SSH

After the computer and the robot are on the same 2.4GHz Wi-Fi, run this in Windows PowerShell or a Linux / macOS terminal:

ssh user@microduck.local

Then:

cd ~/microduck
PYTHONPATH=src .venv/bin/python src/main.py

Stop with q. If the program is still running, open another SSH session:

ssh user@microduck.local
cd ~/microduck
PYTHONPATH=src .venv/bin/python src/stop.py

Safe shutdown:

ssh user@microduck.local
sudo shutdown -h now

Do not cut power directly. Shut the Pi down first, wait 10 to 15 seconds, then turn off the power switch.

Gamepad Mode

Pair a Bluetooth Gamepad

SSH into the Pi, then run:

bluetoothctl

Inside bluetoothctl:

power on
agent on
scan on
pair XX:XX:XX:XX:XX:XX
trust XX:XX:XX:XX:XX:XX
connect XX:XX:XX:XX:XX:XX
scan off
quit

Replace XX:XX:XX:XX:XX:XX with the detected controller MAC address.

Headless Operation

The image already enables the headless gamepad service. After boot:

When the gamepad is connected, the service disables Wi-Fi to improve 2.4GHz Bluetooth stability. Turn off the controller when you need SSH; Wi-Fi will be restored automatically.

Common Commands

Run these from the microduck/ directory on your development computer:

Updating the Model

The ONNX model exported from mjlab_microduck/ should be placed at:

microduck/src/agents/walk.onnx

Then sync:

cd microduck
make sync

The next run will load the new walk.onnx.

Rebuilding a Release Image

After the Pi system, dependencies, services, and model have been tested, the SD card can be turned into a new microduck.img.xz.

Recommended workflow:

1. Test make run or headless gamepad mode on the real robot.
2. Shut down the Pi and insert the SD card into your computer.
3. Clone the full card to a local .img file.
4. Clean sensitive information only inside the cloned image:
   • Wi-Fi credentials.
   • SSH host keys.
   • User SSH keys.
   • /etc/machine-id.
   • cloud-init state.
   • shell history, logs, and apt cache.
5. Reset bootfs/network-config to placeholder values.
6. Verify that ~/microduck/src/agents/walk.onnx, .venv, and microduck-gamepad.service exist.
7. Use PiShrink to create microduck.img.xz.
8. Compute SHA256 and record the checksum in the README or Release notes.

Detailed steps are in:

microduck/docs/dev/clone_sd.md

Directory Layout

.
├── README.md
├── microduck/
│   ├── Makefile
│   ├── src/
│   │   ├── main.py
│   │   ├── scheduler.py
│   │   ├── robot_controller.py
│   │   ├── imu_reader.py
│   │   ├── agents/walk.onnx
│   │   └── moves/walk.py
│   ├── systemd/
│   └── docs/
└── mjlab_microduck/
    ├── src/mjlab_microduck/
    └── logs/

Troubleshooting

microduck.local Cannot Be Found

Wait 1 to 3 minutes first. If it still cannot be found:

• Make sure the Wi-Fi is 2.4GHz.
• Make sure the YAML indentation in network-config is unchanged (method 1).
• If you used method 2, run nmcli device wifi list and hostname -I on the Pi to confirm it joined 2.4GHz Wi-Fi and has an IP.
• Check the Pi's IP address in your router.
• Login with ssh user@<IP>.

SSH Says Host Key Changed

The release image regenerates SSH host keys on first boot. If your computer previously connected to another card, clear the local entry:

ssh-keygen -R microduck.local
ssh-keygen -R <IP>

Servos Do Not Move or Communication Fails

Check:

• Battery voltage.
• OpenRB-150, servo bus, Raspberry Pi power, and common ground.
• Servo IDs match the table above.
• Dynamixel baud rate is 1Mbps.
• OpenRB-150 USB serial port is detected.
• Cable order, splitters, and connector direction.

SSH Disconnects When the Gamepad Connects

This is expected in headless mode. The service disables Wi-Fi when the gamepad is connected to improve Bluetooth stability. Turn off the controller and Wi-Fi will be restored.

The Robot Falls Immediately

Hold the robot first, then check:

• Left/right leg servo IDs are not swapped.
• Knee offsets match the physical assembly.
• IMU mounting orientation is correct.
• walk.onnx matches the current hardware.

Safety Notes

• Hold the robot during the first run.
• Do not test near the edge of a table.
• Do not run for a long time on low battery.
• Do not cut power directly. Use make shutdown or the gamepad shutdown gesture first.
• Before charging or powering on, check for shorts, polarity, and insulation.