Micro Synth

A microcontroller-based digital synthesizer built with the PIC16F1718 that receives MIDI input and generates real-time audio output using wavetable synthesis. Watch on YouTube.

Features

• MIDI 1.0 Compliance: Receives note-on and note-off messages via standard MIDI protocol
• Three Waveforms: Sine, sawtooth, and square wave synthesis
• Real-time Audio: 29.4 kHz sampling rate with 8-bit DAC output
• Monophonic Operation: Single-note melody playback
• Visual Feedback: LED indicators for system status and MIDI activity
• Educational Design: Breadboard-friendly for learning and experimentation

Hardware Requirements

Core Components

• PIC16F1718 microcontroller (28-pin DIP)
• 6N138 opto-isolator for MIDI input
• LM386 audio amplifier
• TL082 op-amp for low-pass filter
• Standard electronic components (resistors, capacitors, LEDs)

MIDI Interface

• DIN5 connector for MIDI input
• MIDI-compliant keyboard or controller

Development Tools

• MPLAB PICkit 5 In-Circuit Debugger
• MPLAB X IDE for development

Technical Specifications

Parameter	Value
Microcontroller	PIC16F1718
Clock Frequency	16 MHz
Sampling Rate	29.4 kHz
DAC Resolution	8-bit
Wavetable Length	4,096 samples
MIDI Baud Rate	31.25 kBaud
Note Range	MIDI notes 48-72 (C3-C5)
Audio Output	Mono, amplified

Software Architecture

Key Features

• Interrupt-driven MIDI processing using EUSART
• Timer0-based audio sampling at 29.4 kHz
• Wavetable synthesis with pre-calculated waveforms
• Integer-based phase accumulation for efficient real-time operation

Waveform Generation

• Sine Wave: Pure fundamental frequency using lookup table
• Sawtooth Wave: Rich harmonic content with anti-aliasing filter
• Square Wave: Odd harmonics only, calculated in real-time

Getting Started

Prerequisites

• MPLAB X IDE (latest version)
• MPLAB XC8 Compiler
• PICkit 5 programmer/debugger

Building the Project

1. Clone this repository

   git clone https://github.com/charlesmulder/microsynth.git
   cd microsynth

2. Open the project in MPLAB X IDE

   • File → Open Project
   • Navigate to the cloned directory
   • Select the project

3. Build the project

   • Build → Build Project (Ctrl+F11)

4. Program the PIC16F1718

   • Connect PICkit 5 programmer
   • Run → Program Device (Ctrl+F5)

Hardware Setup

1. Assemble the circuit on a breadboard following the schematic

2. Connect the PICkit 5 programmer:

   PICkit 5    →    PIC16F1718
   Pin 1 (MCLR) →   Pin 1
   Pin 2 (VDD)  →   Pin 20
   Pin 3 (GND)  →   Pins 8,19
   Pin 4 (PGD)  →   Pin 28
   Pin 5 (PGC)  →   Pin 27
   

3. Connect peripherals:

   • MIDI keyboard to DIN5 connector
   • Speaker to audio output

Usage

LED Status Indicators

LED Color	Status	Description
Green	MIDI Activity	On when note is playing
Yellow	Framing Error	EUSART error (auto-reset)
Red	Buffer Overrun	Requires restart

MIDI Channel Selection

• Channel 1: Sine wave
• Channel 2: Square wave
• Channel 3+: Sawtooth wave

Supported MIDI Messages

• Note-on (0x90-0x9F)
• Note-off (0x80-0x8F)
• Running status for efficient message handling

Circuit Schematic

The complete circuit includes:

• MIDI input isolation circuit
• PIC16F1718 microcontroller
• Audio amplifier with gain control
• 2-pole Butterworth low-pass filter (14.7 kHz cutoff)
• LED status indicators

See the full project documentation for detailed schematics and component values.

Limitations

• Monophonic: Only one note can play at a time
• Pitch Accuracy: Integer sampling increments cause slight pitch deviations
• Limited Range: 25-note range to avoid pitch collisions
• No Polyphony: Multiple notes will overwrite each other

Ethical Considerations

This project prioritizes:

• Sustainability: Breadboard assembly for component reuse
• Hearing Safety: Users advised about volume exposure risks
• Educational Value: Open-source design for learning

Future Enhancements

Potential improvements include:

• Polyphonic capability
• ADSR envelope generation
• Real-time filter controls
• Additional waveforms
• Higher sampling rates
• MIDI CC parameter control

Project Structure

microsynth/
├── src/                    # Source code
│   ├── main.c             # Main application
│   ├── midi.c             # MIDI processing
│   ├── wavetables.c       # Waveform data
│   └── interrupts.c       # Interrupt handlers
├── inc/                   # Header files
├── docs/                  # Documentation
└── README.md            # This file

License

This project is open source. Please credit the original work when using or modifying.

Author

Charles Mulder
Bachelor of Engineering in Electronic and Computer Engineering
Atlantic Technological University Sligo

• Website: charlesmulder.net
• LinkedIn: linkedin.com/in/charlesmulder
• GitHub: github.com/charlesmulder

Project Details:

• Completed: May 2025
• Supervisor: Fabian Connolly

Acknowledgments

• MIDI Manufacturers Association for MIDI specification
• Microchip Technology for PIC16F1718 documentation
• Academic supervisors and peers for guidance and feedback
• Open source community for inspiration and tools

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This synthesizer demonstrates the intersection of embedded systems design, digital signal processing, and music technology - combining technical precision with creative expression.

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