What do you do if you want the convenience of MIDI but the warm tones of analog synths? Build a MIDI to CV converter, of course! In this project, you'll use a QT Py RP2040 running CircuitPython with an MCP4725 DAC to convert MIDI messages to a gate output and 1V/oct output. 

The build is housed in a snazzy 3D printed skull adorned enclosure. The output jacks are located in the skull's eyes.

The CircuitPython code converts MIDI NoteOn and NoteOff messages to gate out and 1V/oct signals that are sent through the two mono audio jacks. This lets you play your CV controlled synths with a MIDI keyboard or a MIDI song file from your DAW.

The MCP4725 DAC is a digital to analog converter and outputs the voltages to correspond with the expected 1V/oct value.

What is 1V/oct?

1V/oct is a standard for controlling pitch in modular synthesis. A volt is divided to correspond with the twelve pitches in western music. For example, 0.333V is pitch E-2 and 0.917V is pitch B-2. When the voltage is increased by 1V, the octave increases by 1. For example, 1.333V is pitch E-3 (an increase of 1V and 1 octave) and 2.917V is pitch B-4 (an increase of 2V and 2 octaves).

However, these pitches are approximate and depend on a variety of factors, such as your oscillator's tuning and any electrical interference. But that's half the fun of synthesis!

Prerequisite Guides

Parts

Video of hand holding a QT Py PCB in their hand. An LED glows rainbow colors.
What a cutie pie! Or is it... a QT Py? This diminutive dev board comes with one of our new favorite chip, the RP2040. It's been made famous in the new
$9.95
In Stock
Vertical Breadboard-Friendly 3.5mm Mono Headphone Jack with audio cable plugged in
Pipe audio in or out of your project with this very handy breadboard-friendly audio jack. It's a mono jack with a disconnect pin so you'll get a ground sleeve pin, a left tip...
$1.25
In Stock
Angled shot of MCP4725 Breakout Board - 12-Bit DAC w/I2C Interface.
Your microcontroller probably has an ADC (analog -> digital converter) but does it have a DAC (digital -> analog converter)??? Now it can! This breakout board features the...
$4.95
In Stock
Top view of Adafruit Perma-Proto Quarter-sized Breadboard PCB.
Customers have asked us to carry basic perf-board, but we never liked the look of most basic perf: it's always crummy quality, with pads that flake off and no labeling. Then we...
$2.95
In Stock
Silicone Cover Stranded-Core Wire - 30AWG in Various Colors laid out beside each other.
Silicone-sheathing wire is super-flexible and soft, and its also strong! Able to handle up to 200°C and up to 600V, it will do when PVC covered wire wimps out. We like this wire...
Out of Stock
Angled shot of coiled pink and purple USB cable with USB A and USB C connectors.
This cable is not only super-fashionable, with a woven pink and purple Blinka-like pattern, it's also made for USB C for our modernized breakout boards, Feathers, and...
$2.95
In Stock
1 x Short Break-away Male Header
36-pin 0.1" Short Break-away Male Header - Pack of 10
1 x Short Female Header
36-pin 0.1" Short Female Header - Pack of 5
1 x M2.5 screws
M2.5 screws and stand-offs

This guide was first published on Aug 02, 2022. It was last updated on 2022-08-02 16:56:26 -0400.

This page (Overview) was last updated on Aug 10, 2022.

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