Development Guide

This section covers building Mikro.js firmware from source, writing drivers for sensors and peripherals, shipping C/C++ with a package as a native module, and describing development boards as board packages.

What you can contribute

• Drivers: code for a sensor, display, motor controller or other peripheral. A driver is JavaScript on the core APIs, or a native module when it needs C or C++.
• Native modules: C/C++ that a package ships, compiled into the firmware and imported by its package specifier.
• Board packages: prebuilt firmware for a development board, and optionally the board's pin names and drivers wired to its pins.
• Core runtime: Bug fixes, performance improvements, and new platform APIs in packages/@mikrojs/native/.

Prerequisites

• Node.js >= 24
• pnpm >= 10.30
• direnv (loads the repo's .envrc, so the mikro CLICommand-Line Interface runs from source)
• ESP-IDFEspressif IoT Development Framework prerequisites for your platform: see Espressif's setup guide
• A USBUniversal Serial Bus cable and an ESP32 development board (for on-device testing)

Getting the source

git clone --recurse-submodules https://github.com/mikrojs/mikro.git
cd mikro
pnpm install

If you already cloned without submodules:

git submodule update --init --recursive
pnpm install

This installs all workspace dependencies and builds the qjsc bytecode compiler (used during firmware builds).

What's next

• Custom Firmware: build and distribute custom firmware from npm packages
• Building from Source: set up ESP-IDFEspressif IoT Development Framework and build firmware from the monorepo
• Creating Drivers: write a driver for a peripheral in JavaScript
• Native Modules: ship C/C++ with a package, compiled into the firmware
• Creating Boards: define a board package with pin maps and sdkconfig
• Architecture: how the build system, module registration, and bytecode pipeline work