2 layers152.4 × 68.6 mm Pico test synth2, the printed circuit board in 3D

Pico test synth2

Simple board to help make synths with Raspberry Pi Pico/Pico2 and PCM5102 I2S DAC

Size: 152.4 × 68.6 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 55
Nets: 65
Pads: 217
Tracks, vias: 358, 47
Pours: 3
Routed: Yes
KiCad: KiCad 9.0 (file 20241229)
Created: 8 Aug 2023
Updated: 9 Sep 2026

Overview

Pico test synth2 is an open-source printed circuit board by todbot, from the todbot/pico_test_synth repository on GitHub, published under the MIT licence. It is a 2-layer board of 152.4 × 68.6 mm with 55 parts on 65 nets, routed with 358 tracks and 47 vias.

It is built around the H11L1. Its parts include 22 resistors, 2 ICs, 2 connectors, 1 capacitor and 1 diode. It belongs with the audio and music boards and the RP2040 and RP2350 boards of this library.

Main components

H11L1
DIP-6-55℃~+100℃ 1 1.6mA 1Mbit/s 250mW 3V~15V 5kV DC DIP-6 Logic Output Optoisolators ROHSEverlight ElectronicsLogic Output Optoisolators

README

README.md

pico_test_synth

A simple Raspberry Pi Pico RP2040 or Pico 2 RP2350-based synth to experiment with synthio and Mozzi.

pico_test_synth2

pico_test_synth, the original

video demo

** Available on Tindie **

Features

PCM5102 I2S DAC footprint for high-quality stereo audio out
Optoisolated MIDI Input via MIDI TRS-A 3.5mm jack
MIDI output via MIDI TRS-A 3.5mm jack
Two pots for controlling parameters
One switch for controlling parameters
16 capsense touch buttons for synth triggering
USB MIDI in/out of course too
(NOTE: the pico_test_synth1 PCB will NOT work with the Pico2, since its RP2350 chip has a hardware error)

pico_test_synth2 vs pico_test_synth

Both use the same components
Both run the same code
Both fit in the same enclosure
pico_test_synth2 drawn in Kicad; pico_test_synth drawn in Eagle
pico_test_synth2 has square buttons; pico_test_synth has round buttons
pico_test_synth2 can work with Pico 2 and Pico
pico_test_synth can only work with Pico1

Software

Programs written for qtpy_synth will work with this board too with minimal changes.

Some programs written specifically for this board:

TBish - a TB303-like synth demo (video demo)
monosynth1 - a full Moog-like monosynth written in Arduino & Mozzi
hwtest - test out the hardware with a simple synth (video demo)
wavesynth - port of wavesynth for qtpy_synth board with some improvements

Enclosure

As seen in the photos, there is a simple 3d-printable enclosure available on Printables. It's fast to print and you can snap the PCB in to quickly get started, or use M2.5 screws and nuts to secure the PCB more permanently.

Pins used

The board uses all of the Raspberry Pi Pico pins:

board.GP28 - middle button
board.GP27 - right knob
board.GP26 - left knob
board.GP22 - I2S data
board.GP21 - I2S LR clock
board.GP20 - I2S bit clock
board.GP19 - I2C SCL for OLED display
board.GP18 - I2C SDA for OLED display
board.GP17 - TRS UART MIDI in
board.GP16 - TRS UART MIDI out
board.GP15..board.GP0 -- touch pads 1-16

For more details see hwtest/code.py.

Schematics

pico_test_synth2

pico_test_synth, original

Parts

Qty	Value	Footprint	References
16	1M	Resistor_SMD:R_0603_1608Metric	R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16
16	CapButton	todbot_stuff:Pad-CapTouch-11_2mm-roundrect	TP1, TP2, TP3, TP4, TP5, TP6, TP7, TP8, TP9, TP10, TP11, TP12, TP13, TP14, TP15, TP16
4	MountingHole	MountingHole:MountingHole_2.7mm_M2.5	H1, H2, H3, H4
3	4.7k	Resistor_SMD:R_0603_1608Metric	R19, R21, R22
2	9mm_NoDet_10k_DShaft	PCM_4ms_Potentiometer:Pot_9mm_DShaft	POT1, POT2
2	AudioJack4	todbot_stuff:Jack_3.5mm_PJ320D_Horizontal	J1, J2
1	10	Resistor_SMD:R_0603_1608Metric	R17
1	100n	Capacitor_SMD:C_0603_1608Metric	C1
1	1N4148	Diode_SMD:D_SOD-123	D1
1	200	Resistor_SMD:R_0603_1608Metric	R20
1	33	Resistor_SMD:R_0603_1608Metric	R18
1	H11L1	easyeda2kicad:SMD-6_L7.3-W6.5-P2.54-LS10.2-BL	IC1
1	Pico	todbot_RPI_Pico:RPi_Pico_SMD_TH	U1
1	SW_Push	Button_Switch_THT:SW_PUSH_6mm_H4.3mm	SW1
1	SolderJumper_2_Bridged	Jumper:SolderJumper-2_P1.3mm_Bridged_RoundedPad1.0x1.5mm	JP1
1	SolderJumper_2_Open	Jumper:SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm	JP2
1	~	todbot_eagle2023:I2S_PCM_5100_SOUNDCARD	MODULE1
1	~	todbot_stuff:OLED-TH_over_L27.8-W27.2-P2.54_C9900033791	DISP1

Questions

How big is the Pico test synth2 PCB?

It measures 152.4 × 68.6 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Pico test synth2 use?

55 parts, built around the H11L1. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Pico test synth2 KiCad files?

From the todbot/pico_test_synth repository on GitHub, at the commit this page was made from: the board is schematics/pico_test_synth2/pico_test_synth2.kicad_pcb and its schematic schematics/pico_test_synth2/pico_test_synth2.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Pico test synth2 design in my own project?

Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).

Category and platform

Audio and music RP2040 RP2350

Topics

circuitpython i2s raspberrypipico rp2040 synthdiy synthesizer synthio rp2350

Project files

Show this board on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/boards/todbot-pico-test-synth" title="Pico test synth2 in PCBKit" width="100%" height="480" style="border:0;border-radius:12px" allow="fullscreen" loading="lazy"></iframe>

A picture

<img src="https://pcbkit.io/embed/boards/todbot-pico-test-synth.jpg" alt="Pico test synth2" width="1200" height="900">

A picture that opens the board, for a README

[![Pico test synth2](https://pcbkit.io/embed/boards/todbot-pico-test-synth.jpg?size=s)](https://pcbkit.io/boards/todbot-pico-test-synth)

Source

Repository: todbot/pico_test_synth
Board file: schematics/pico_test_synth2/pico_test_synth2.kicad_pcb
Commit: a1d80de
Licence: MIT

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