Espruino: JavaScript on Microcontrollers

Introduction

Espruino is a JavaScript interpreter designed for microcontrollers, enabling developers to write and run JavaScript code directly on low-power embedded devices. Unlike traditional firmware that requires compilation, Espruino allows real-time scripting, making IoT development faster and more interactive.

This guide explores Espruino’s features, installation process, supported hardware, and examples to get started.

Why Use Espruino?

Espruino simplifies microcontroller programming by offering:

• Real-time JavaScript execution: No need for compilation; code runs instantly.
• Low memory footprint: Optimized for resource-constrained devices.
• Event-driven programming: Ideal for handling sensors and IoT applications.
• Web-based development: The Espruino Web IDE provides an easy-to-use interface for writing code.

Compared to C/C++, Espruino reduces complexity and accelerates development, making it a great choice for beginners and web developers transitioning to embedded systems.

Supported Hardware

Espruino runs on a variety of microcontrollers, including:

• Official Espruino Boards: Espruino Original, Espruino Pico, and Espruino WiFi.
• ESP8266 & ESP32: Low-cost Wi-Fi-enabled microcontrollers.
• STM32 Boards: STM32F1 and STM32F4-based boards.
• Nordic nRF52: Bluetooth Low Energy (BLE) enabled microcontrollers.

For optimal performance, it is recommended to use official Espruino boards, though third-party boards like the ESP8266 are also supported.

Installing Espruino on NodeMCU (ESP8266)

To use Espruino on NodeMCU, follow these steps:

1. Download Espruino Firmware

• Visit Espruino’s official website and download the ESP8266 firmware.

2. Flash the Firmware

• Install esptool.py (Python-based flashing tool):

  pip install esptool
  

• Connect the NodeMCU board to your PC and run:

  esptool.py --port /dev/ttyUSB0 write_flash -fm dio -fs 4MB 0x00000 espruino_esp8266.bin
  

3. Connect to Espruino

• Use a serial terminal (like PuTTY) or the Espruino Web IDE to connect and start programming.

Getting Started with Espruino

Once Espruino is installed, you can interact with it via the Web IDE or a serial terminal.

Example 1: Blink an LED

setInterval(function() {
  digitalWrite(D4, !digitalRead(D4));
}, 1000);

This code toggles the LED on and off every second.

Example 2: Read a Sensor (DHT11)

I2C1.setup({scl: D5, sda: D4});
var dht = require("DHT11").connect(D2);
setInterval(function() {
  console.log("Temperature: " + dht.read().temp);
}, 2000);

This reads temperature data from a DHT11 sensor every 2 seconds.

Example 3: Simple Web Server

var wifi = require("Wifi");
wifi.connect("SSID", {password:"PASSWORD"}, function() {
  console.log("Connected to WiFi");
  require("http").createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.end("<h1>Hello from Espruino!</h1>");
  }).listen(80);
});

This sets up a simple web server that responds with an HTML message.

Comparison: Espruino vs Traditional Embedded Programming

Feature	Espruino (JavaScript)	C/C++ (Arduino)
Ease of Use	High	Moderate
Compilation	Not required	Required
Performance	Moderate	High
Memory Usage	Low	Moderate
Community Support	Growing	Large

Espruino is ideal for rapid prototyping, while C/C++ is better for performance-critical applications.

Conclusion

Espruino makes microcontroller development more accessible by allowing JavaScript programming on embedded devices. Whether you are a beginner or an experienced developer, Espruino provides a flexible and efficient way to develop IoT applications.

Would you like more Espruino tutorials? Let us know in the comments!

You may like also:

• ESP Easy
• IoT with ESP8266
• ESP32 BLE with DHT11
• ESP32 BLE on Arduino IDE with UART Test
• ESP32 Bluetooth Low Energy (BLE) on Arduino IDE
• ArduinoOTA ESP32: Wi-Fi (OTA) Wireless Update from the Arduino IDE
• Arduino ESP32 support on Windows and Ubuntu
• ESP32 with LoRa using Arduino IDE
• Arduino Support for ESP8266 with simple test code