Wheeliebot

A small self-balancing, wheel-legged robot driven from your phone over WiFi. Two brushless gimbal motors run the wheels, two STS3032 serial-bus servos lift the legs, an MPU-6050 keeps it upright, and an ESP32 ties it all together. It self-balances within ~2 seconds of being lifted off the ground — and yes, it jumps.

Full build (BOM, prints, photos, assembly): Wheeliebot on Printables

⚠️ 2026-05 — controller PCB v2 in progress. I found design issues with the current controller PCB and I'm working on a revision. Firmware and assembly steps below are still accurate; don't fab boards from this repo until v2 lands.

This firmware is derived from the open-source Navbot-EN01 project by fuwei007. The chassis, controller PCB, and documentation are my adaptation; the firmware and FD calibration tooling come from the upstream project.

What's in this repo

wl_pro_robot/
  wl_pro_robot.ino       # main sketch (entry point)
  robot.{h,cpp}          # balance + drive control
  cpu0_task.{h,cpp}      # tasks pinned to ESP32 core 0
  wifi.{h,cpp}           # WiFi AP + control endpoint
  web_socket_client_util.*  # WebSocket transport for the phone UI
  basic_web.h            # the web UI served to your phone (HTML/JS blob)
  ble.{h,cpp}            # BLE control path
  Servo_STS3032.{h,cpp}  # STS3032 leg-servo driver (serial bus)
  ssd1362.{h,cpp}        # OLED status display
  oled_font.h            # font glyphs for the OLED
  feedback_util.*        # status / feedback helpers
  eeprom_util.*          # persisted calibration in EEPROM
  define.h
  libraries/             # bundled, version-pinned dependencies — install from here
    ArduinoJson/
    SCSservo/            # STS3032 / SCS / SMS bus protocol
    MPU6050_tockn/       # IMU
    Simple_FOC/          # field-oriented control for the gimbal motors

Pin assignments live in robot.h and Servo_STS3032.h. They will be promoted into a table here once the v2 PCB is finalized — pinning them in two places before the board respin is asking for drift.

Build environment

Pinned versions (newer ESP32 cores break the bundled servo lib — do not use a newer board package):

Tool	Version
Arduino IDE	2.3.4
ESP32 board package (Espressif)	2.0.3 (pin this)
Target board	ESP32 Dev Module
Partition scheme	No OTA (Large APP) — default partitioning is too small for this binary

Libraries: install from this repo's wl_pro_robot/libraries/ directory, not from the Arduino Library Manager. The bundled versions are pinned against API breakage in newer releases.

Flashing the firmware

1. Clone this repo.
2. Open wl_pro_robot/wl_pro_robot.ino in Arduino IDE 2.3.4.
3. In Tools → Board Manager, install ESP32 by Espressif v2.0.3.
4. Copy each folder under wl_pro_robot/libraries/ into your Arduino libraries/ folder, or let the IDE pick them up from the sketch directory.
5. Set Tools → Board to ESP32 Dev Module.
6. Set Tools → Partition Scheme to No OTA (Large APP).
7. Connect the ESP32, select the COM port, and Upload.

Servo zero-position calibration

Before first run, both STS3032 leg servos need their zero positions set and unique bus IDs (left = 1, right = 2). The Printables build guide covers this end-to-end with photos — see the Firmware & calibration section there.

Short version: upload the SteeringEngineDebug sketch from the upstream Navbot-EN01 toolchain, run the FD calibration tool, calibrate one servo at a time with the other unplugged from the bus, and assign IDs. Reconnect both when done.

If Tools/SteeringEngineDebug and Tools/FD1984-240227/ aren't present in this repo, grab them from the upstream Navbot-EN01 repo.

First run

1. Plug a 7.4 V 1100–1500 mAh LiPo into the XT30.
2. Power switch on. Red LED + a few seconds of self-test.
3. Phone → join WiFi network navbot_en01-XXXXXX (password 12345678).
4. Open http://192.168.1.11 in your phone browser.
5. Tap Robot Go, lift the bot off the ground for ~2 seconds, set it down, drive.

Troubleshooting

• Sketch won't compile, errors about SCServo or Simple_FOC — you're picking up a different version from ~/Arduino/libraries. Either delete the duplicate or move the bundled wl_pro_robot/libraries/<name> to override it.
• Sketch too large / partition errors — partition scheme isn't set to No OTA (Large APP).
• Servos twitch or don't respond after upload — IDs collide on the serial bus. Re-run servo zero-position calibration with one servo unplugged at a time and assign IDs 1 and 2.
• WiFi navbot_en01-XXXXXX doesn't appear — power-cycle. If it still doesn't show, USB into the ESP32 and check serial for boot messages.
• 192.168.1.11 doesn't load — your phone is on your home WiFi, not the bot's AP. Recheck the connected network.
• Self-balance never settles — check MPU-6050 wiring on I²C, confirm the bot was held still during boot self-test (the IMU calibrates against gravity at startup).

License

Derived from Navbot-EN01 by fuwei007. License inheritance pending — see LICENSE once added.

TODO: Confirm the upstream license and add a matching LICENSE file before this repo is considered properly published.

Contributing / feedback

Issues and PRs welcome. If you build one, post a make on the Printables listing — I read every comment.

Build resources

• Bill of Material