MIDI PWM Controller

Arduino-based PWM controller with MIDI and Serial input support. Controls three PWM channels on pins 9, 10, and 11 via MIDI Control Change messages or direct serial commands.

Hardware

• Arduino (Uno, Nano, or compatible)
• MIDI Input: Pin 4 (via optocoupler circuit, 31250 baud)
• PWM Outputs: Pins 9, 10, 11

See fritzing/ directory for circuit diagrams.

Features

• MIDI Control: CC messages for direct PWM control
• Serial Control: Simple text commands via USB serial
• Smooth Ramping: Gradual PWM transitions for smooth motor/LED control
• Safety Timeout: Auto-shutoff when MIDI signal is lost (disabled for serial control)

MIDI Mapping

Control Change	PWM Channel	Arduino Pin
CC 20	Channel 1	Pin 9
CC 21	Channel 2	Pin 10
CC 22	Channel 3	Pin 11

CC values 0-127 map to PWM 0-255.

Note Control (Optional)

Note-based control is enabled by default:

Note	PWM Channel	Arduino Pin
C4 (60)	Channel 1	Pin 9
D4 (62)	Channel 2	Pin 10
E4 (64)	Channel 3	Pin 11

Velocity maps to PWM intensity.

Serial Commands

Connect via USB at 115200 baud. Commands are case-insensitive.

Command	Description	Example
A<0-255>	Set PWM channel 1 (pin 9)	A255 = full on
B<0-255>	Set PWM channel 2 (pin 10)	B128 = 50%
C<0-255>	Set PWM channel 3 (pin 11)	C64 = 25%
s	Show status
0	All channels off

Note: Serial control disables the MIDI timeout, so values persist until explicitly changed.

Building

This project uses PlatformIO.

# Build
pio run

# Upload
pio run --target upload

# Monitor serial
pio device monitor

Testing Tools

MIDI Test Script

Python script for testing MIDI control:

# Run all demos (requires uv or install mido + python-rtmidi)
./test_midi.py

# Interactive mode
./test_midi.py -m interactive

# Available modes: sweep, individual, wave, notes, interactive, all
./test_midi.py -m wave -d 10

Serial Control GUI (Streamlit)

Web-based GUI for serial control:

# Run with uvx (recommended - isolated environment)
uvx --with pyserial streamlit run serial_control.py

# Or install dependencies globally and run
pip install streamlit pyserial
streamlit run serial_control.py

Configuration

Edit constants in src/main.cpp:

// MIDI CC numbers
#define CC_PWM_1 20
#define CC_PWM_2 21
#define CC_PWM_3 22

// Note control (set to false to disable)
#define ENABLE_NOTE_CONTROL true

// Safety timeout (ms) - set to 0 to disable
static const uint16_t MIDI_TIMEOUT_MS = 400;

// Ramping (for smooth transitions)
static const uint8_t  RAMP_STEP      = 3;   // PWM change per tick
static const uint16_t RAMP_PERIOD_MS = 2;   // tick period

License

MIT