Key features
How it works
Chiptune Sounds from Go-On Pico
Control Commands
Sound Types
Hardware
Key Libraries
Build Instructions
Why I Made This
What’s Next
GO-On Pico

Published August 22, 2025 © GPL3+

Go-On Pico: 8-Bit Style Synthesis Module

Go-On Pico (五音ピコ) is a retro-inspired synthesis module designed for generating chiptune-like sounds with M5Stack Core.

IntermediateFull instructions provided3 hours130

Go-On Pico: 8-Bit Style Synthesis Module

Things used in this project

Hardware components

M5Stack Core2 ESP32 IoT Development Kit

Seeed Studio XIAO RP2040

M5Stack BUS Module

Software apps and online services

Arduino IDE

PlatformIO IDE

Story

Go-On Pico (五音ピコ) is an original chiptune sound module I created specifically for the M5Stack Core2! My goal was to make it easy for anyone to produce retro game-like sounds and, ultimately, to experiment with vocal synthesis using formant techniques. While MIDI synthesizers and external sound modules exist, there wasn’t a module designed for the M5Stack Core that could generate chiptune sounds or mimic vocal synthesis in a fun, accessible way—so I decided to build one!

Go-On Pico module for M5Stack core2

Key features

8bit style Piko Piko sounds (2CH Square wave, 1CH Triangle wave, 1CH Noise, 1CH Wave memory) *Note1
Easy control via serial port
Module for M5Stack core2

Note1: Wave memory will be available soon.

How it works?

Here’s how you can use Go-On Pico to create chiptune sounds!

Chiptune sounds from Go-On Pico

Chiptune Sounds from Go-On Pico

Controlling Go-On Pico from the M5Stack Core2 is super simple!

Open pins 13 and 14 with Serial.begin on the M5Stack Core2. Then, send commands by writing to the serial interface.

Control Commands

The command format is:

command,ch,note,velocity

Play a sound: 1,0,60,127
Plays a note on the specified channel with MIDI note 60 and velocity 127.
Stop a sound: 0,0,60,127
Stops the note on the specified channel

Sound Types

CH0: Square wave
CH1: Square wave
CH2: Triangle wave
CH3: Noise

Hardware

Microcontroller: Seeed Studio XIAO RP2040 (based on Raspberry Pi RP2040 chip, compact form factor for easy integration)

Audio Amplifier: MAX98357A I2S Amp (handles generated digital audio input from XIAO RP2040).

Speaker: 8Ω 1W speaker (small, low-power unit; sourced from an M5Stack Synth Unit in the prototype).

M5Stack BUS moudle: Mount XIAO RP2040, MAX98357A and the speaker.

Host Device: M5Stack Core2 (provides UART communication, power supply, and touch interface for control).

Additional Components:

Wires/jumpers for connections (UART, power).

Optional: Volume control potentiometer (connected via ADC for analog volume adjustment).

Key Libraries

Mozzi: An Arduino library for waveform synthesis. In Go-On Pico, it’s used on the XIAO RP2040 to generate sound.

Build Instructions

The prototype is built by assembling the necessary components onto an M5Stack BUS module.

Refer to the circuit diagram for component connections.

1. Attach pin headers to the XIAO RP2040 and mount it onto the BUS module.

2. Attach pin headers to the I2S amplifier (MAX98357A) and mount it onto the BUS module.

3. Connect the XIAO RP2040’s GPIO, 3.3V, and GND pins to the I2S amplifier.

4. Connect the speaker to the I2S amplifier.

5. Connect MBUS pins 13 and 14 to the XIAO RP2040 for UART communication.

6. Connect MBUS 5V and GND to the XIAO RP2040 for power.

7. Verify all wiring for accuracy.

8. Connect the XIAO RP2040 to a PC via USB cable.

9. Clone Go-On Pico core from Github and put XIAO RP2040 into boot mode and flash the firmware.

Done!

Why I Made This

With high-performance microcontrollers and peripherals making voice synthesis easier than ever, something felt off to me. I believe microcontrollers are at their most exciting when they’re pushed to their limits with constrained resources. Perfection isn’t the goal—there’s beauty in creating something that feels "just right" despite those limitations! That’s what I love about this approach.

For Go-On Pico, I drew inspiration from projects like AquesTalk Pico, a voice synthesis chip/library that achieves impressive results on a humble ATMega328P (the same chip in an Arduino Uno). I was also inspired by YouTube videos showcasing people making Game Boy hardware "sing" by cleverly manipulating its sound chip. These examples fueled my desire to craft a retro-inspired audio module that captures the charm of chiptune sounds using minimal resources.

What’s Next?

Vocal Synthesis: Tune formant synthesis capabilities to mimic singing voices more effectively.
Envelope: Add envelope control for dynamic sound shaping (e.g., attack, decay, sustain, release).
Waveform Memory: Implement waveform memory channel for custom or sampled sounds.

GO-On Pico?

The name "Go-On Pico" derives from "five sounds" (五音[go-on] in Japanese), referencing the M5Stack's "5" and the planned 5-channel audio setup (square wave x2, triangle wave x1, noise x1, waveform memory x1).

Code

Go-On Pico Controller

#include <M5Unified.h>

void sendSerialMessage(uint8_t command, uint8_t channel, uint8_t tone, uint8_t velocity) {
    char message[20];
    sprintf(message, "%02d,%02d,%03d,%03d\n", command, channel, tone, velocity);
    Serial2.print(message);
    Serial.print(message);
}

void setup() {
    auto cfg = M5.config();
    M5.begin(cfg);
    Serial.begin(115200);
    Serial2.begin(115200, SERIAL_8N1, 13, 14);

    M5.Display.setTextSize(2);
    M5.Display.setCursor(0, 40);
    M5.Display.println("BtnA: C4");
    M5.Display.println("BtnB: D4");
    M5.Display.println("BtnC: E4");
}

void loop() {
    M5.update();

    // BtnA → C4
    if (M5.BtnA.wasPressed()) {
        sendSerialMessage(1, 0, 60, 67); // note_on C4
        Serial.println("BtnA was pressed");
    }
    if (M5.BtnA.wasReleased()) {
        sendSerialMessage(0, 0, 60, 0);   // note_off C4
        Serial.println("BtnA was released");
    }

    // BtnB → D4
    if (M5.BtnB.wasPressed()) {
        sendSerialMessage(1, 0, 62, 67); // note_on D4
        Serial.println("BtnB was pressed");
    }
    if (M5.BtnB.wasReleased()) {
        sendSerialMessage(0, 0, 62, 0);   // note_off D4
        Serial.println("BtnB was released");
    }

    // BtnC → E4
    if (M5.BtnC.wasPressed()) {
        sendSerialMessage(1, 0, 64, 67); // note_on E4
        Serial.println("BtnC was pressed");
    }
    if (M5.BtnC.wasReleased()) {
        sendSerialMessage(0, 0, 64, 0);   // note_off E4
        Serial.println("BtnB was released");
    }
}

Credits

NANANA

1 project • 1 follower

MAKE is fun! Obsessed with all things KAWAII! Follow me on X(@nananauno)

Go-On Pico: 8-Bit Style Synthesis Module