Unleash XIAO’s Musical Potential: A Budget-Friendly Eurorack Solution, MIDI Keyboard Integration, and More!

XIAO is a series of thump-sized boards with a compact design, thump-sized form factor, powerful processors, and rich peripherals. As a complete microcontroller, it can act as a building block for larger systems to simplify the process of designing and building complex electronic systems by providing a pre-integrated and tested platform that can be easily integrated into larger systems. By using it, you can focus on creating the unique features and functions of your system, without having to worry about the time and effort involved in integrating and testing the individual components.

XIAO has been adopted into a wide range of musical-related prototypes. It’s great to see the continued success of the application in this aspect and its impact on the music industry. Having a series collection to showcase the details of these prototypes is a great way to bring visibility to the XIAO’s potential in this aspect. By showcasing the various prototypes and the unique ways that XIAO has been integrated, you can visualize the versatility and capabilities of this platform.

All we hope is to give talented individuals and teams one more option to bring their ideas to life!

A [ $8 ] Eurorack Modular Synth Sample Drum with Seeed Studio XIAO ESP32C3

1-shot sample drum module with a Seeed XIAO ESP32C3 development board with 48 samples storage,  48kHz sample rate, and 10-bit output.

Eurorack is a modular synthesizer system that was introduced in the 1980s and has since become a popular platform for electronic music production. A Eurorack system consists of individual modules, each with its own specific function, that can be connected together in a variety of ways to create a wide range of sounds and musical structures. They are also highly expandable, allowing users to add new modules and continue to grow their systems over time.

>> Challenge

The cost of a Eurorack modular synthesizer system can vary greatly, depending on the size of the system and the individual components included. At the lower end of the cost spectrum, you can find basic Eurorack starter kits for around $300 to $500. Mid-range Eurorack systems can cost anywhere from $800 to $1500.

>> A Budget-friendly Choice for Eurorack Device

XIAO ESP32C3 is cheap, has 4Mbytes of storage, and can be developed on an Arduino. Samples are stored in the flash memory of the ESP32C3 MCU.

[ $9 ] DIY Eurorack modular synth CHORD VCO v2 with Seeed XIAO RP2040 

RP2040 based 5 polyphonic CHORD VCO, easy to play a chord progression. Built-in quantizer and autoharmonics.

Synthesis techniques in Eurorack refer to the various methods used to generate and manipulate sound in a modular synthesizer system.


The time required to learn and use synthesis techniques in Eurorack can vary greatly depending on the individual and their experience with synthesis and electronic music production. For some, the learning process can be quite quick and intuitive, as the basic concepts of synthesis are relatively straightforward and easy to understand. However, for others, it can be more time-consuming, especially if they are unfamiliar with the basic principles of synthesis or the operation of modular synthesizer systems.

>> Solution

A unique and innovative module for a Eurorack system that is based on XIAO RP2040. This module is designed to be a 5-voice polyphonic voltage-controlled oscillator (VCO) with a built-in quantizer and autoharmonics, making it easy to play chord progressions. By incorporating these features into a single module, you’re making it easier for musicians and producers to create complex musical sounds without the need for multiple modules or a deep understanding of synthesis techniques.

Portami: Battery-powered polyphonic synth designed to be a companion to small MIDI keyboards Powered by XIAO SAMD21

Portami is a musical instrument, specifically a portable polyphonic synth. A polyphonic synth is a type of synthesizer that can play multiple notes simultaneously, as opposed to a monophonic synth, which can only play one note at a time.

>>Why Build a companion to small Midi keyboards

A companion to a small Midi keyboard is useful because it allows the keyboard to be used as a musical instrument in its own right, without the need for additional equipment. Additionally, having a companion synth for a small Midi keyboard can provide more creative options and sound-shaping capabilities than just using the keyboard by itself.


Its implementation focuses on USB Midi communication (Midi-in through the onboard USB-C port) and features a push button to cycle between wave types (sine, saw, square, pulse, triangle, and noise). An RGB led inside the button changes color according to the current wave type. Other than the onboard speaker driven by an LM386 amplifier, Portami has a 3.5″ mini-jack port to plug a pair of headphones. The audio socket has a switching mechanism, disconnecting the speaker when in use. The whole setup is powered by a 3.7V, 1100mAh Li-ion battery, recharged, and protected by a TP4056 USB-C charger module. A regulator boosts the voltage to 5V, providing power to the Midi keyboard.

Digital Audio Player (DAP) using XIAO SAMD21

What is DAP?

A digital audio player (DAP) is a device designed for playing digital audio files, typically in the MP3 or other popular music file format. They are sometimes called “portable media players” or simply “music players”. The cost of a Digital Audio Player (DAP) can vary depending on several factors such as the brand, features, and performance. Entry-level DAPs can cost around $50 to $100, while high-end models can cost several hundred dollars or more. Some factors that can impact the cost of a DAP include the type of storage (e.g. internal memory or removable storage), the audio codec support, the quality of the built-in amplifier, and the type of output options (e.g. headphone jack, balanced outputs, etc.).


XIAO SAMD21 is small in size, power-efficient, and budget-friendly cost ($5.40). The following features make it a good choice for building your DAP.

  • affordable cost and easy for mass production
  • Small size: 21 x 17.5mm, compact and lightweight, ideal for projects that require minimal space.
  • high performance: with a 48 MHz ARM Cortex-M0+ processor, XIAO SAMD21 provides fast and efficient performance, making it ideal for projects that require high computational power.
  • wide compatibility: compatible with a wide range of development environments and software, making it easy to program and integrate with other devices and systems.

multi – MIDI controller/filter/router, sound generator Based on XIAO SAMD21

A MIDI controller is a device that sends musical information, such as note data, modulation data, and control change data, to a sound generator or other musical instrument or equipment. A MIDI filter is a device that modifies or processes MIDI data in some way, such as changing the velocity of incoming notes or transposing the data to a different key. A MIDI router is a device that routes MIDI data from one or more input sources to one or more output destinations, allowing for flexible and customizable MIDI signal flow.

multi is an open hardware circuit board hosting a Seeed Studio XIAO SAMD21, 6 pots, 2 pushbuttons, 2 Midi DIN connectors, and audio output. The Seeed Studio XIAO SAMD21 board carries a powerful ATSAMD21G18A-MU which is a low-power microcontroller and has 14 GPIO PINs, a DAC output, and one UART interface. To avoid grounding loops the MIDI input is properly optoisolated, as required by official specifications. You can program multi as you need, using the Arduino IDE. On the MIDI side, possible use includes advanced midi controlling, filtering, and remapping as well as algorithmic arpeggiators and aleatoric patch generators.

Visual-nome Powered by XIAO SAMD21


  • Single button interface, short press to start/stop.
  • ‘tap to set BPM’ by long press when stopped. Metronome starts automatically after 5 taps.
  • An indicator runs around the ring every measure / bar (4 beats).
  • Whole ring flashes on every beat. Downbeat or upbeat configurable.
  • First beat accented (stronger flash, higher buzz tone)

MIDI-Lighting-Keyboard-XIAO Based on XIAO SAMD21

 Let’s play the Midi sound source with Seeed Studio XIAO SAMD21!

A FM Oscillator on XIAO SAMD21

We are continually amazed by the imaginative solutions and innovative ideas generated by the community, and we are eager to see even more cutting-edge applications in the future. As a leading provider of IoT hardware solutions for digital pioneers, our goal is to enable both makers and enterprises to bring their products and services to life. If you have any inquiries regarding XIAO’s role in this area, please don’t hesitate to reach out to Min Liang at [email protected] for more information.

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January 2023