Scalable Servo Control with TouchDesigner and PCA9685

A control system for driving arrays of hobby servos in paired 2-DOF X/Y configurations, using TouchDesigner and an ESP32 microcontroller.

Overview

The system sends OSC messages over UDP from TouchDesigner to an ESP32, which routes them through a PCA9685 driver board to control servo pairs. The prototype drives 12 servos across 6 paired mechanisms. The architecture scales to larger arrays by adding driver boards.

Three control modes are available in the TouchDesigner network: live gesture control via Leap Motion, a manual slider UI, and pre-programmed keyframe sequences through the Animation COMP.

Signal Flow

[Leap Motion] ---> (USB HID) ---> [TouchDesigner]
[TouchDesigner] ---> (Wi-Fi / OSC UDP) ---> [ESP32] ---> (I²C) ---> [PCA9685] ---> (PWM) ---> [12x Hobby Servos]

2-DOF pairing. Servos are organized in X/Y pairs throughout the system. TouchDesigner sends paired values, the ESP32 parses them as pairs, and the PCA9685 channels map to the physical mechanism layout.

OSC over UDP. TouchDesigner sends OSC messages to the ESP32's IP address over the local network. For permanent installations, switching to a wired serial connection is more reliable than Wi-Fi.

Control Modes

• Gesture: Leap Motion tracks hand position in real time. TouchDesigner maps it to servo targets and streams values over UDP.
• Manual: Slider UI gives direct control over the X and Y axes for all servo pairs.
• Animated: TouchDesigner's Animation COMP drives repeatable keyframe sequences. A Python script inside the .toe file generates the keyframe table from a pose table, so sequences are defined as data rather than manually edited curves.

Repository Contents

ESP32/

• touchdesigner-udp-com.ino: Connects to Wi-Fi, listens for OSC messages, and controls the X/Y servo pairs via the PCA9685.

TouchDesigner/

• motor-control-system_005v2-1.toe: Control network with switchable inputs for Leap Motion, manual sliders, Animation COMP, and a reset position.

Hardware

ESP32 development board

PCA9685 16-channel PWM servo driver

EMAX ES08MA II hobby servos, or similar

Leap Motion Controller gesture sensor

5 V power supply for servo power rail

Software

• TouchDesigner
• Arduino IDE with the ESP32 board manager installed
• Arduino libraries: Adafruit_PWMServoDriver, OSC

Setup

1. Open touchdesigner-udp-com.ino and set your Wi-Fi ssid and password.
2. Upload the sketch to the ESP32.
3. Open motor-control-system_005v2-1.toe in TouchDesigner. Update the IP address in the OSC Out CHOP to match the ESP32.
4. Use the mode buttons in the network to switch between Leap Motion, manual, and animated control through the switch_inputMaster CHOP.

Keyframe Generation

The .toe file includes a Python script called generate_keys_script. It reads servo poses from the null_table_keys table and generates the correctly formatted keys table for the Animation COMP. Defining poses as table rows is faster than editing animation curves by hand and makes sequences easier to rearrange or extend.

Links

• Project Write-up
• Gesture-Controlled 2-Axis Mechanisms