Moddable SDK

Modern software development for microcontrollers

The Moddable SDK is a combination of development tools and runtime software to create applications for microcontrollers.

Microcontrollers are highly constrained devices compared to modern computers and mobile devices. A typical microcontroller used with the Moddable SDK has about 45 KB of free memory, 1 MB of Flash ROM, and runs at 80 MHz. The Moddable SDK uses many different techniques, both at build time and at run time, to work efficiently on these devices.

The primary programming language for development is JavaScript. The XS JavaScript engine at the center of the Moddable SDK implements the 2025 JavaScript language standard with better than 99% conformance.[1] The constraints of the target microcontroller may limit the number of language features that can be used in combination by a single application.

The JavaScript language implemented in the Moddable SDK is the same language used in web pages and Node.js. The microcontroller that the scripts run on, however, is very different from a personal computer, server, or mobile device. These differences often require a different approach to using JavaScript. The APIs and objects in the Moddable SDK are quite different, being designed with the goal of minimizing memory use. Bring your existing experience with JavaScript, but be prepared to think about performance, code size, and memory use in a different way.[2]

As much as practical, the Moddable SDK is implemented in JavaScript. Portions of the Moddable SDK are implemented in C for performance or direct access to native APIs.[3] There is no C++.

A significant part of building efficient software for microcontrollers occurs at build time. The Moddable SDK contains many tools and options for the build process.[4] Take time to learn about these to get the best results.

[1] See also: XS Conformance [2] See also: XS Differences [3] See also: XS in C [4] See also: Tools, manifest

Major features

Networking

The Moddable SDK implements network sockets and a variety of standard, secure networking protocols built on sockets including HTTP/HTTPS, WebSockets, MQTT, mDNS, DNS, SNTP, and telnet.

There is also Bluetooth Low Energy (BLE) protocol support for both BLE peripheral and central device development.

Graphics

Two APIs for building modern user interfaces are available:

Commodetto, a bitmap graphics library that provides a 2D graphics API. Commodetto includes the lightweight Poco rendering engine, a display list renderer able to efficiently render a single scanline at a time, saving considerable memory by eliminating the need for a frame buffer.
Piu, a user interface framework built on top of Commodetto. Piu is an object-based framework that makes it easier to create complex, responsive layouts.

The Moddable SDK also includes command line tools for image format conversion, image compression, image rotation, font compression, localization, and more. The build system automatically makes use of these tools.

Hardware

The Moddable SDK implements a variety of hardware protocols including digital (GPIO), analog, PWM, and I2C. A number of drivers for common off-the-shelf sensors and corresponding example apps are also available.

Source level debugger

The xsbug JavaScript source level debugger is a full-featured debugger that supports debugging modules and applications for XS platforms.

Similar to other debuggers, xsbug supports setting breakpoints, browsing source code, and inspection of the call stack and variables. The xsbug debugger additionally provides real-time instrumentation to track memory usage and profile application and resource consumption.

See also: xsbug documentation

Getting Started

To do anything with the Moddable SDK, you have to install it on your computer. This involves downloading this repository, installing some development tools, configuring settings over the command line, and building the Moddable SDK tools.

The Getting Started Guide in the documentation directory walks you through the whole process of installing the Moddable SDK.
With the Moddable SDK installed, you can build and run apps on hardware simulators.
To develop for a particular device, you need to install additional tools and SDKs for that device. The setup process for each device is different, but usually involves installing some additional SDKs, drivers, and development tools.

The SDKs and tools for a particular device are not created or maintained by Moddable, but we do provide detailed instructions to help you install them and get started developing for them with the Moddable SDK. The section below provides links to the setup instructions/developer guides for some of the devices we support.

Hardware simulators

The Moddable SDK includes simulators that run on macOS, Linux, and Windows. These are a great way to get started, and are invaluable as development accelerators.

To use the simulator, you simply need to install the Moddable SDK.

A video demonstration and information about the simulator is available in the Simulator section of the tools documentation.

ESP8266 by Espressif

To use the Moddable SDK with ESP8266-based devices, you need to:

Install the Moddable SDK
Install ESP8266 tools

The Moddable SDK supports many devices built on ESP8266, including the devices shown below.

| | | | | :---: | :---: | :---: | | <a href="./documentation/devices/moddable-one.md"><img src="./documentation/assets/devices/moddable-one.png" width=125></a> Moddable One[5] | <a href="./documentation/devices/esp8266.md"><img src="./documentation/assets/devices/esp8266.png" width=125></a> Node MCU ESP8266[6] | <a href="./documentation/devices/moddable-three.md"><img src="./documentation/assets/devices/moddable-three.png" width=125></a> Moddable Three[7]

[5] See also: Moddable One Developer Guide, Moddable product page [6] See also: Using the Moddable SDK with ESP8266 [7] See also: Moddable Three Developer Guide

ESP32 by Espressif

To use the Moddable SDK with ESP32-based devices, you need to:

Install the Moddable SDK
Install ESP32 tools

The Moddable SDK supports many devices built on ESP32, ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6 and ESP32-H2, including the devices shown below.

| | | | | :---: | :---: | :---: | | <a href="./documentation/devices/moddable-six.md"><img src="./documentation/assets/devices/moddable-six.png" width=125></a> Moddable Six[8] | <a href="./documentation/devices/esp32.md"> ESP32 </a> Node MCU ESP32[9] | <a href="./documentation/devices/esp32.md#platforms"> M5Stack </a> M5Stack | <a href="./documentation/devices/esp32.md#platforms"></a> M5Stack Fire | <a href="./documentation/devices/esp32.md#platforms"></a> M5Stick C | <a href="./documentation/devices/esp32.md#platforms"> M5Atom </a> M5Atom Matrix

[8] See also: Moddable Six Developer Guide, Moddable product page [9] See also: Using the Moddable SDK with ESP32

Pico by Raspberry Pi

To use the Moddable SDK with Pico devices, you need to:

Install the Moddable SDK
Install Pico tools

The Moddable SDK supports many devices built with the Raspberry Pi Pico, including the boards shown below:

| | | | | :---: | :---: | :---: | | <a href="./documentation/devices/pico.md"><img src="./documentation/assets/devices/pi-pico_w.png" width=65></a> Raspberry Pi Pico W | <a href="./documentation/devices/pico.md"><img src="./documentation/assets/devices/pico-display.png" width=65></a> Pimoroni Pico Display | <a href="./documentation/devices/pico.md"><img src="./documentation/assets/devices/pico-ili9341.png" width=120></a> ili9341 | <a href="./documentation/devices/pico.md"><img src="./documentation/assets/devi

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