OpenCat ESP32 Complete Guide: Build & Program GitHub's Top Open-Source Quadruped Robot (2026)

"I want to build and program my own quadruped robot."

That's exactly what the open-source framework OpenCat ESP32 delivers. With 360 stars on GitHub, this project runs on the ESP32-based "BiBoard" control board and powers the robot dog Bittle X and robot cat Nybble Q under the fully open-source MIT license.

A Boston Dynamics-style quadruped robot you can build from a kit starting at roughly $319 (with the new Quaddle desktop model from $99). You can progress from block-based coding to Python, C++, and even ROS — a platform actually used in K-12 classrooms up to university research labs.

This guide covers how OpenCat ESP32 works, choosing the right hardware, setting up the dev environment, and concrete examples of what you can build.

• GitHub repository: github.com/PetoiCamp/OpenCatEsp32-Quadruped-Robot
• Official docs: docs.petoi.com
• Petoi store: petoi.com

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What Is OpenCat ESP32?

Bottom line: OpenCat ESP32 is an open-source quadruped robot firmware/framework that runs on the ESP32 dual-core "BiBoard" controller.

Buy the robot body (Bittle X / Nybble Q) and you get an assemble-it-yourself kit; rewrite the code and you can add your own behaviors and AI features. It's designed not just as a fun pet but as a learning platform for quadruped locomotion, IoT, AI vision, and reinforcement learning.

OpenCat is a long-running project started in 2018 — over 30,000 robots shipped to 60+ countries, cited in 20+ academic papers. A platform with real track record in both education and research.

(Video: official Petoi demo on YouTube)

Supported Hardware

OpenCat ESP32 runs on the current-generation robots powered by the ESP32-based BiBoard.

Prices from the Petoi store as of September 2026 — check the official site for current pricing.

The older Bittle/Nybble (NyBoard, ATmega328P) are discontinued; current models all run BiBoard. For an older Bittle, use the legacy OpenCat repo (github.com/PetoiCamp/OpenCat).

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Why ESP32 (BiBoard)?

The old NyBoard was adequate for walking but underpowered for real robotics development. BiBoard fixes all of that.

In short: the evolution from "make it walk" to "make it a research platform." A 240MHz dual-core handles real-time servo coordination and camera-based AI processing simultaneously. Built-in Wi-Fi and Bluetooth mean wireless control and data streaming with no dongles.

Both hardware and software are fully open source under the MIT license — fork it to build your own robot, or use it freely in research.

BiBoard V1 Key Specs

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Assembly & First Setup

Assembling Bittle X takes about 60 minutes per the official guide — no soldering, designed for ages 10+. The flow:

1. Assemble the kit — frame, servos, legs per the manual, then mount the BiBoard
2. Connect via mobile app — over the BiBoard's built-in Bluetooth
3. Joint calibration — set the neutral positions on all axes with the app's Calibrator
4. Drive it — run 35+ lifelike movements from the app's Controller

No code needed up through calibration. First enjoy it as a finished robot pet, then start hacking.

(Video: official "Bittle Gap Jump" demo on YouTube)

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Modifying the Firmware (Arduino IDE)

Here's where OpenCat ESP32 shines. Rewrite the GitHub firmware from the Arduino IDE and add your own behaviors.

Setting Up the Environment

1. Add ESP32 board support to Arduino IDE — add the ESP32 board URL in Preferences, then install "esp32" from Boards Manager
2. Use version 2.0.12 — versions 2.0.13+ are reported to prevent startup (per official docs)
3. Download the OpenCatEsp32 repo — if you grab the Zip, rename the folder from OpenCatEsp32-main to OpenCatEsp32 (must match the .ino name)
4. Install libraries — ArduinoJson, WebSockets, MU Vision Sensor

Board Settings (ESP32 Dev Module)

Set the Device Macro and Upload

Edit the macros at the top of OpenCatEsp32.ino:

#define BITTLE    // 9-DOF robot dog: 1 head + 8 legs
// #define NYBBLE  // 11-DOF robot cat: 2 head + 1 tail + 8 legs

If you attached the robotic arm, also enable #define ROBOT_ARM. Then connect via USB Type-C and hit Upload.

Open the serial monitor (115200 baud, No line ending) to watch the boot log for I2C device detection and firmware version.

Sensor Expansion

The BiBoard has Grove sockets for official extension modules:

• Petoi AI Vision — object recognition and person detection via MU vision sensor
• Ultrasonic distance sensor — obstacle avoidance
• Raspberry Pi / NVIDIA Jetson integration — offload heavy AI over serial UART

Official tutorials cover NVIDIA Isaac simulation, reinforcement learning, and SLAM with ROS — the platform scales from "toy" to "research bench."

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The Programming Learning Path

You don't start by writing C++. OpenCat ESP32 is built for gradual progression — one reason it's used in education:

1. Block coding — drag-and-drop on iPad/Android tablets
2. Python — the step after Petoi Coding Blocks; adding voice commands is a popular example
3. C++ (Arduino IDE) — modify the firmware itself: new gaits, sensor integration
4. ROS / ROS2 — research level: SLAM, navigation, reinforcement learning

Free official curricula are used in K-12 schools, colleges, and robotics camps — with roughly 15 hours of lessons published at no cost.

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Who It's For (and Who It Isn't)

Great fit for:

• Students and researchers serious about legged robotics
• Parents and educators teaching both coding and hands-on building
• Hobbyists who want a Boston Dynamics-style quadruped on a budget
• Anyone needing a small ROS / RL test platform

If you just want a finished robot with no assembly, other products fit better. OpenCat ESP32 is a platform for people who enjoy building and hacking.

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Watch the New "Quaddle"

Launched on Kickstarter September 2, 2026, Quaddle is a breakthrough low-DOF design: an omnidirectional quadruped on just 4 servos. Retro-mechanical legs drive a full knee lift from a single motor, slashing cost.

• Builder ($99 super early bird): 90+ movements, Raspberry Pi Zero socket
• Buddy ($139): open-domain AI chat, Learn & Replay by hand
• Scout ($179): built-in gesture, light, and infrared sensors for research

At $149–$269 MSRP it's far cheaper than Bittle X ($319). A very attractive entry line — general availability after the Kickstarter is worth watching.

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Conclusion: Bittle X Now, or Wait for Quaddle?

Two clear options:

• Want serious quadruped robotics now → Bittle X ($319)
• On a budget / equipping a classroom → wait for Quaddle (from $99)

The real value of OpenCat ESP32 is that it's both a consumer robot toy and an open-source learning platform. 360 stars may look modest, but in the quadruped niche it's GitHub's most-starred platform, backed by academic citations.

Start by browsing the GitHub repository to gauge the codebase and community activity.

• GitHub: PetoiCamp/OpenCatEsp32-Quadruped-Robot
• Official docs: docs.petoi.com
• Education curricula: Petoi Education

This site participates in the Amazon Associates and other affiliate programs. This is an independent explainer article.

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