Build your own synthesizer with keypad note inputs and knobs for parameter controls! At the heart of this instrument is the DSP-G1 MIDI synthesizer voice chip — an analog modeling synth by Jan Ostman that can read in MIDI data for notes and control change (CC) messages, and outputs sound to play over any powered speakers, headphones, or amplifier system!

The DSP-G1 makes beautiful, classic paraphonic synth sounds, similar to the famous 1980s Roland Juno-6. You can play up to five notes at once, each with three oscillators, and you can dial in multiple wave shapes, detuning, LFO, 24db filter, ADSR envelopes for the amplifier and filter, and more!
The Feather M0 Express can read your Trellis keypad buttons and potentiometer knobs and then send these commands to the synth chip as MIDI messages.

The Trellis Feather DSP-G1 synthesizer code is configured to play eight note scales in three octaves, in both momentary and held (latching) modes, with the bottom row of eight keypads reserved for input functions. But, there’s nothing to stop you from turning it into a step sequencer, random note generator,  chording machine, or who knows what!

If you'd like to use Trellis keypads to send MIDI through USB or Bluetooth to your computer, search for "MIDI" in the Learn Guide search bar!

You can watch the build from the livestream here:


Listed below are the parts you use to build your synthesizer.

1 x Feather M0 Express
Designed for CircuitPython ATSAMD21 Cortex M0
1 x DSP-G1
MIDI Synth Voice Chip
1 x 8 Pin IC Socket socket
for 8-pin 0.3” Chips
1 x Adafruit Perma-Proto
1/2 Sized Breadboard PCB
1 x Short Feather Headers Kit - Male
12-pin and 16-pin Set
1 x Short Feather Headers Kit - Female
12-pin and 16-pin Set
1 x Right angle male header pins 10 pack
Break-away 36-pin strip (10 pack)
6 x Panel Mount 10k Potentiometer
Breadboard Friendly 10k Linear
6 x Potentiometer Knob
Soft Touch T18 White
2 x Adafruit Trellis Monochrome Driver PCB
for 4x4 Keypad and 3mm LEDs
1 x Slim Metal Knob
10mm dia. x 10mm T18
1 x Multi-Colored Heat Shrink Pack
3/32” + 1/8” + 3/16” Diameters
1 x Large Single Row Housing Pack
for DIY Jumper Cables
1 x Small Single Row Wire Housing Pack
for DIY Jumper Cables
1 x Hook-up Wire Spool Set
22AWG Solid Core 10 x 25ft
1 x Panel Mount Extension USB Cable
Micro B Male to Micro B Female
1 x USB Cable
A/MicroB - 3ft

Material & Tools

In addition to the parts above, you'll also want a cardboard box, roughly 9"x6"x3" in size to use as an enclosure.

Tools required are a soldering iron with solder, box cutter or hobby knife, diagonal cutters, and a pair of wire strippers. You may already have these, but if not, here are some suggested tools:

This guide was first published on Apr 30, 2018. It was last updated on Apr 10, 2024.

This page (Overview) was last updated on Mar 08, 2024.

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