Octal Brushed Controller

Octal Motor Driver

An 8-channel H-bridge motor driver assembly with controller, designed for parade float kinematic animation. Two units (one per side of the float) drive up to 16 geared motors to create spinning pinwheel scenes. Remote control is provided via the DMX 512 show control protocol.

Features

• Up to 8 motor channels per box, one box per side of the float
• DMX 512 remote control from a master animation station
• Local control interface with four modes: disabled, manual, local animation, and remote DMX
• Motor power: 12–24 VDC with gearhead motors; target speed 0–10 RPM
• 20 kHz PWM motor control for smooth, quiet operation
• Default motor driver: DRV8871 (up to 2 A per channel, off-the-shelf breakout boards)
• Optional high-current driver: BTS7960 (up to 43 A per channel, via ribbon cable to driver blocks)
• Up to 8 limit/endstop inputs (one per motor channel) for travel limits and auto-homing

System Architecture

Top-Level Flow

1. The ESP32 UI board receives commands from the master animation controller over the DMX 512 bus.
2. The operator selects the control source (remote DMX, local manual, or local automatic) on the UI board.
3. The UI board sends the resolved 8-channel direction and speed commands to the Raspberry Pi Pico motor controller over I2C.
4. The Pico generates PWM outputs to the motor drivers. Speed is commanded as a percentage from −100% to +100%, which maps directly to direction and PWM duty cycle.
5. Optional endstop inputs can halt motion in a given direction (TBD).

Power Distribution

An optional isolated DC:DC converter on the DMX receiver decouples local ground from the DMX bus to prevent ground shifts during high-current motor activity.

Hardware

ESP32 User Interface Board (ESP32-2432S028R "Cheap Yellow Display")

An off-the-shelf development board with a 2.8" touchscreen display.

• On-board power for display, CPU, and touch interface
• Connectors for 5 V in, I2C bus, and GPIO (configured for DMX serial input)
• ESP32 supports Wi-Fi and Bluetooth for future wireless control options

Front	Back

References:

• Random Nerd Tutorials — CYD Guide
• ESP32 Cheap Yellow Display (GitHub)

DMX 512 Serial Converter

Provides robust, long-range serial connection to the master animation controller.

Option 1 — RS422 converter board (half-duplex) Connect R+, R−, and GND to the DMX D+, D−, and GND lines; connect GND and TXD to the CYD serial input.

Option 2 — SparkFun DMX interface board Provides full isolation via optoisolators and an isolated DC:DC converter, protecting against voltage shifts from high-current motor activity. Wire GND, 5 V, 3.3 V, and RX pins to the CYD board.

Motor Controller — Raspberry Pi Pico (RP2040)

Generates PWM signals for all 8 motor drivers.

• 16 PWM outputs (2 per channel — direction and speed)
• 8 endstop switch inputs for motor homing
• Dual-core RP2040 (see Software section)

Motor Driver — DRV8871 (default)

Available from Adafruit or Amazon clones. Datasheet: adafruit-drv8871-brushed-dc-motor-driver-breakout.pdf

Motor Driver — BTS7960 (optional, high current)

Uses the same PWM signals as the DRV8871. Current monitoring pins are available. Datasheet: BTS7960-Motor-Driver.pdf

Board	Pinout

Octal Motor Controller PCB (KiCad)

Custom PCB housing the Raspberry Pi Pico, DRV8871 motor driver sockets, power regulation, and all interconnects.

KiCad project: Hardware/Kicad/Octal_Brushed_Controller/

Software

Both firmware projects use PlatformIO with the Arduino framework. Open each project folder in VS Code with the PlatformIO extension installed — it will auto-detect the platformio.ini and resolve dependencies.

Software/Octal_Motor_Drive_UI — User Interface Application (ESP32)

Runs on the ESP32-2432S028R board. Handles:

• DMX 512 receive and decode
• Touchscreen UI for mode selection and manual motor control
• Local animation sequencer
• I2C command output to the motor controller

Software/Octal_Motor_Drive_Controller — Motor Controller Application (Pico)

Runs on the Raspberry Pi Pico (RP2040). Utilizes both CPU cores:

CPU0

• Communicates with the UI board over I2C
• Monitors endstop limit events
• Updates PWM outputs to motor drivers based on commands and endstop state

CPU1 (watchdog)

• Monitors the I2C bus for timeouts
• Shuts down all motors if the UI node stops sending updates

PWM outputs run at 25 kHz to eliminate audible motor noise.

Repository Structure

Octal_Motor_Controller/
├── README.md
├── Octal_Motor_Driver.docx          # Full design document
├── System_Diagram.drawio            # Editable system diagrams
├── System_Diagram-Top Flow.png
├── System_Diagram-Power.png
├── Hardware/
│   ├── Kicad/
│   │   └── Octal_Brushed_Controller/   # KiCad PCB project
│   └── Parts/                          # Datasheets and reference docs
└── Software/
    ├── Octal_Motor_Drive_UI/           # ESP32 UI PlatformIO project
    └── Octal_Motor_Drive_Controller/   # Pico motor controller PlatformIO project