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YOU CAN BUILD A PALM-SIZED ROBOT DOG THAT DOES BACKFLIPS

A quadruped robot small enough to hold in one hand that walks, runs, balances on two legs, and does backflips — and you program every move.

by Petoi (Rongzhong Li and team)

FULL CAD BOM FIRMWARE DOCS

RoboticsOpen-hardware

difficulty
●●●○○
time
a weekend-plus
license
MIT
repo
repo ACTIVE4,988 stars

WHAT YOU’LL NEED

  • Electronic parts — full list with part numbers in the repo BOM
  • Dev board / microcontroller — runs the project firmware
  • Soldering kit + basic tools — one-time buy, serves every future build

Partner

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1

COMPAREE VERDICT

Bittle is a serious robotics platform dressed as a toy dog. The OpenCat firmware lets you program gaits, reactions, and tricks in Arduino C++ or Python, and the community has already written skills for voice commands, object tracking, and remote control. The backflip is real — it is a pre-programmed sequence you trigger, not something you teach from scratch — but writing your own behaviours is where the weekend disappears. The kit build itself is straightforward if you have ever assembled a complex model, but calibrating eight servo motors so the legs move in sync is the part that will take longer than the instructions suggest. Most people underestimate how much trial-and-error goes into making a quadruped walk smoothly. If you want a platform to learn inverse kinematics and gait planning without building the chassis from scratch, this is it. If you expected to design and 3D print your own robot dog, you are in the wrong project — the mechanics are closed and you are buying them.

NOT IN THE REPO

  • —OpenCat is the firmware framework, not mechanical files — Bittle itself is a commercial kit you buy assembled or unassembled
  • —The GitHub repo contains Arduino/ESP32/Raspberry Pi code, calibration tools, Python API, and extensive motion/behaviour documentation
  • —No STL files — the mechanical design is proprietary to Petoi, the software stack is open
  • —Licence is Apache 2.0 for firmware, permits commercial use with attribution
  • —Active repo with frequent updates and a large community — 30+ language skills, mobile app integration, and voice control examples included
  • —You can also buy a fully assembled version if you want to skip mechanical build entirely and go straight to programming

Can I build this?

Printnothing required — Bittle is a purchased kit, mechanical files are not open
BuyBittle kit (unassembled or assembled versions available from Petoi), plus Arduino IDE or Raspberry Pi for programming
Toolssmall screwdriver set for kit assembly, USB cable for firmware upload, computer for calibration and code upload
Skillsintermediate — assembly is model-kit level, programming requires Arduino/Python comfort and patience for servo calibration
Timeweekend-plus — kit assembly is 3-4 hours, calibration and first working gait another 4-6 hours, custom behaviours as long as you want
Cost$$ — kit price dominates, no additional hardware needed unless you add sensors or a Raspberry Pi for advanced features
SafetyNone beyond ordinary electronics care — low-voltage servos, no sharp edges, safe for a desk. Keep small screws away from young children during assembly.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

A desktop 3D printer that prints in full colorPartner · Kickstarter
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See how it prints

Gallery

upload://cmrvtacen0ghsri1zdupkhfea/upload-cdba3d64.jpg

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Read the OpenCat repository README and decide whether you want Arduino, ESP32, or Raspberry Pi control (firmware and API are all here, but mechanical files are not — you buy the kit from Petoi)
  2. 2.Order the Bittle kit (assembled or unassembled) directly from Petoi(not sold through the GitHub repo — check Petoi's official site for current availability)
  3. 3.Follow the assembly guide if you bought the unassembled kit, then upload the calibration sketch(calibration takes longer than assembly — every servo needs individual tuning for smooth movement)
  4. 4.Install the Arduino IDE or set up the Python API, upload the OpenCat firmware, and start with the example gaits(the backflip is one of the included skills — you trigger it, you do not write it from scratch)

KNOWN ISSUES

  • Bittle is a commercial kit with open firmware, not a fully open design — you cannot 3D print the body or source the servos separately at the same cost
  • Servo calibration is the single longest part of the build and the instructions make it sound faster than it is — expect to iterate
  • The backflip and other flashy moves are pre-programmed — writing your own complex gaits requires solid understanding of inverse kinematics
  • If a servo arrives misaligned or drifts after assembly, recalibration is fiddly — keep the calibration sketch and notes handy
  • The Python API requires a serial connection and is slower than direct Arduino control — pick your control method before you start coding
  • Community support is active but scattered across Discord, forums, and GitHub issues — finding answers takes patience

Can I 3D print my own Bittle instead of buying the kit?

No — the mechanical design is proprietary and the STL files are not published. The OpenCat firmware is open, the chassis is not.

Do I need a Raspberry Pi or can I use just Arduino?

Arduino alone is enough for all the core gaits and skills. Raspberry Pi adds computer vision, voice control, and network features, but it is optional.

How hard is it to make Bittle do something custom, like fetch a ball?

Object tracking requires a camera and significant coding — the framework supports it, but you are writing the behaviour from scratch. Simpler tricks like sit, roll over, or play dead are easier starting points.

What happens if I break a servo during assembly or testing?

Petoi sells replacement servos, but they are specific to Bittle — generic hobby servos will not fit without modifying the frame, which is not designed for it.

Community builds

No community builds yet — be the first, we feature the best ones.

Discussion1

FROM THE COMPAREE TEAM

The OpenCat repo has over 30 pre-programmed skills and supports Arduino, ESP32, and Raspberry Pi — but the backflip is the one everyone tries first. What would you teach yours to do after that?

CompareeTEAM1mo agoedited

Practical notes from our verification: OpenCat is the firmware, not the full project — Bittle itself is a commercial kit you buy, and the mechanical files are not open-source. The GitHub repo is extensive and actively maintained, with calibration tools, Python API, and mobile app integration, but the time everyone underestimates is servo calibration — it is not hard, just iterative and slower than the assembly itself. The backflip is real and it is pre-programmed, so you get it working quickly, but writing your own gaits from scratch is where the learning curve lives. If you want to program robot behaviour without fabricating the chassis, this is a solid choice. If you wanted to design your own quadruped, you are buying someone else's.

Petoi (Rongzhong Li and team)

Petoi started as a Kickstarter project to make quadruped robotics accessible without requiring a full mechanical engineering background. The OpenCat framework grew into a widely used teaching platform for universities and hobbyists learning legged robot control.

GitHub

Star the project on GitHub

DISCLAIMER

  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
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