ESP32-Powered Robotic Hand with PWM Servo Control

A custom firmware adaptation for the Amazing Hand by Pollen Robotics — redesigned from the ground up to drive standard PWM servos via an Adafruit PCA9685 driver, controlled by an ESP32 with a built-in web interface.

The Problem

The original Amazing Hand design relies on Feetech SCS0009 serial bus servos, which require a dedicated serial protocol and specific hardware to drive. Replacing them with widely available PDI-1109MG PWM servos makes the build cheaper, more accessible, and easier to source — but requires a completely different control layer.

This project replaces the servo driver stack entirely: an ESP32 talks I2C to an Adafruit PCA9685 16-channel PWM board, which in turn drives 8 servos across 4 fingers (2 servos per finger for full flexion control).

Hardware

• ESP32 development board
• Adafruit PCA9685 16-channel I2C PWM driver
• 8× PDI-1109MG PWM servos
• 5V / 3-5A external power supply
• Amazing Hand 3D-printed parts (original Pollen Robotics design)

Important: The PCA9685 board must be powered separately from the ESP32. Driving 8 servos from the ESP32's onboard regulator will cause brownouts and unpredictable behavior.

Wiring

The wiring connects the ESP32 to the PCA9685 over I2C, with each servo channel mapped to a specific finger joint.

Software Architecture

The firmware is built with PlatformIO and structured as a modular, non-blocking state machine. No blocking delays — everything runs cooperatively so the system stays responsive during gesture execution, calibration, or web requests.

Key modules:

• ServoController — wraps the PCA9685 library, translates angular positions to PWM pulse widths
• FingerController — manages each finger's two-servo pair, handles joint coordination
• StateManager — tracks the current system mode (idle, gesture, calibration, demo)
• CalibrationManager — reads/writes per-servo min/max calibration data to NVS (non-volatile storage)
• CommandManager — parses serial input at 115200 baud
• WebInterface — serves a browser UI over Wi-Fi for gesture and calibration control

Gestures

Three pre-programmed gestures are available out of the box:

Wave

Rock & Roll

Middle Finger

Gestures can be triggered via the web interface, serial commands, or cycled automatically in demo mode.

Web Interface

The ESP32 hosts a web server accessible from any browser on the same network. It exposes three panels:

All controls

Gesture shortcuts

Per-finger sliders

Calibration panel

Each servo's min/max pulse width can be tuned individually and saved to persistent storage — no need to reflash to adjust for mechanical tolerances.

Bill of Materials

Component	Qty
ESP32 development board	1
Adafruit PCA9685 PWM driver	1
PDI-1109MG servo	8
5V / 3-5A power supply	1
Amazing Hand 3D-printed parts	1 set

Getting Started

Clone the repo and open it in PlatformIO. Build and flash to the ESP32. On first boot, the device creates a Wi-Fi access point — connect to it and navigate to the device IP to open the web interface.

Full setup instructions and serial command reference are in the GitHub repository.