MIDI Projects with MicroPython

Welcome to the MIDI Projects Section

Monty waving welcome MIDI is the language that musical instruments use to talk to each other. With a Raspberry Pi Pico and a few components, you can build your own MIDI instrument, controller, or sequencer. Let's build something amazing!

What Is MIDI?

MIDI stands for Musical Instrument Digital Interface. It is a standard protocol that lets electronic instruments, computers, and controllers communicate.

MIDI does not send audio — it sends instructions, like: - "Play note 60 (Middle C) at volume 80" - "Stop note 60" - "Change to instrument 25 (steel guitar)"

These instructions are called MIDI messages. A synthesizer or software (like GarageBand or a DAW) receives the messages and produces the actual sound.

Key Idea

Monty thinking Think of MIDI like sheet music. The sheet music tells a musician what notes to play, but the musician (synthesizer) decides what it sounds like. MIDI separates the instructions from the sound.

MIDI on the Raspberry Pi Pico

The Pico can send MIDI messages over its UART serial port at the standard MIDI baud rate of 31 250 bits per second.

To send MIDI to external gear, you need: - A MIDI output circuit (an optocoupler and resistors, or a ready-made board) - A 5-pin DIN MIDI cable

For beginners, the easiest approach is to use USB MIDI by connecting the Pico directly to a computer. The computer sees the Pico as a USB MIDI device.

MIDI Hardware Options

Option	Cost	Notes
Direct UART (serial MIDI)	~$1 in parts	Needs optocoupler circuit
PicoMIDI Development Board (Midimuso)	~$20	All-in-one board with DIN connectors
USB MIDI (software only)	$0	Pico W firmware needed

Projects in This Section

Project	What You Build
MIDI Basics	Send ascending MIDI notes over UART
Chromatic Scale	Play every note in one octave on a MIDI synth
Piano Keyboard	13 buttons that play a full octave
MIDI Sequencer	A looping pattern of notes

Quick Start: Play a Note Over UART

You need: 1. Raspberry Pi Pico 2. MIDI output circuit connected to GP4 (TX1) 3. MIDI synthesizer or computer with a soft synth

from machine import Pin, UART
import time

# MIDI uses 31250 baud — this is the universal MIDI speed
uart = UART(1, baudrate=31250, tx=Pin(4), rx=Pin(5))
uart.init(bits=8, parity=None, stop=1)

def note_on(channel, note, velocity):
    """Send a MIDI Note On message."""
    # 0x90 = Note On command on channel 1 (channels are 0–15)
    uart.write(bytearray([0x90 | channel, note, velocity]))

def note_off(channel, note):
    """Send a MIDI Note Off message."""
    uart.write(bytearray([0x80 | channel, note, 0]))

# Play Middle C (note 60) for one second
note_on(0, 60, 100)   # channel 0, note 60, velocity 100
time.sleep(1)
note_off(0, 60)

MIDI Note Numbers

MIDI uses numbers 0–127 for notes. Middle C is note number 60:

Note	MIDI number
C4 (Middle C)	60
D4	62
E4	64
F4	65
G4	67
A4 (440 Hz)	69
B4	71
C5	72

Monty's Tip

Monty giving a tip You can test MIDI without any hardware by installing a free software synthesizer on your computer, such as VirtualMIDISynth (Windows) or using the built-in IAC Driver (Mac). Connect the Pico via USB and the computer will receive your MIDI messages as if from a keyboard.