Albert Mini — ESP32 Quadruped Robot Dog

Albert is an 8-servo quadruped robot dog powered by an ESP32 and a PCA9685 PWM driver. He walks, spins, dances, does push-ups, and more — all controllable over Serial or Bluetooth.

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Hardware

Component	Details
MCU	ESP32 (any dev board)
Servo Driver	PCA9685 via I²C (0x40)
Servos	8 × standard hobby servos (legs) + 1 × neck servo (channel 15)
Power	5–6 V servo supply, separate from ESP32 logic

Leg layout (servo channels):

  FRONT
 3,2   0,1      ← FL hip/knee, FR hip/knee
 7,6   4,5      ← BL hip/knee, BR hip/knee
  BACK

Even channels → hips, odd channels → knees.

Features

Continuous gaits — run until stopped:

• WALK — diagonal trot with asymmetric knee lift
• LEFT / RIGHT — spin in place

One-shot tricks — play once, then return to idle:

• UP / DOWN — stand / crouch
• PUSHUPS — 5 reps, down-and-up
• SWING — lateral weight shift
• WORM — front-back wave crawl
• GALLOP — fast bounding gait
• JUMP — crouch → explosive extend
• DANCE — head bob + leg shimmy
• UNDULATE — smooth sinusoidal body wave
• STOP — halt all movement

Getting Started

Dependencies

Install via the Arduino Library Manager or PlatformIO:

• Adafruit PWM Servo Driver Library
• Wire (built-in)
• BluetoothSerial (included with ESP32 Arduino core)

Upload

1. Open the .ino file in Arduino IDE (or import into PlatformIO).
2. Select your ESP32 board and COM port.
3. Flash at 115200 baud.
4. On boot Albert stands up and announces Albert 100% Loaded!.

Control

Send commands as newline-terminated strings over Serial (115200 baud) or Bluetooth (device name: Albert_RobotDog):

# Terminal / Serial Monitor
WALK
LEFT
STOP
DANCE

# Any Bluetooth serial app on your phone works too

Commands are case-insensitive.

Tuning

Key constants at the top of the file:

Constant	Default	Purpose
SERVOMIN / SERVOMAX	100 / 500	PWM pulse range for your servos
CENTER	325	Neutral standing pulse
AMPLITUDE	45	Gait swing amplitude (degrees-ish)
FREQUENCY	0.005	Gait speed (higher = faster)
SPEED_FACTOR	0.5	Smoothing factor for idle transitions
MAX_STEP	8	Max pulse change per tick
MOVE_STEPS	35	Interpolation steps for trick transitions
off_set_walk[]	see code	Per-servo offsets to bias the standing posture

If Albert walks crooked, adjust off_set_walk[]. If knees don't lift enough, increase AMPLITUDE or the +20 knee boost in runGait().

Architecture

loop()
 ├─ read Serial / BT command
 ├─ dispatch to mode or one-shot trick
 └─ if walking/spinning → runGait(ampScale[])
    else               → updateAllServos()  (smooth idle hold)

runGait()
 ├─ hips:  CENTER + offset + amp * cos(ωt + φ)
 └─ knees: CENTER + offset + amp * max(0, cos(ωt + φ))   ← half-wave lift

tricks (runDanceSequence, etc.)
 └─ set targetPos[] → moveUntilReachedAll()  (linear interp)

The gait engine uses a simple sinusoidal oscillator with per-servo phase offsets for a diagonal trot pattern. Knees use a half-rectified cosine so they only lift, never push through the floor.

License

MIT — do whatever you want with it. If you build your own Albert, I'd love to see it.