node-web-gpio

GPIO access with Node.js

[!NOTE] Linux only. This library uses the sysfs GPIO interface (/sys/class/gpio) and the native epoll addon for hardware interrupts, neither of which exist on Windows/macOS.

Usage

$ npm i node-web-gpio

import { requestGPIOAccess } from "node-web-gpio";
import { setTimeout as sleep } from "node:timers/promises";

const gpioAccess = await requestGPIOAccess();
const port = gpioAccess.ports.get(26);

await port.export("out");

while (true) {
  await port.write(1);
  await sleep(1000);
  await port.write(0);
  await sleep(1000);
}

Input with hardware interrupts (epoll)

Input ports are watched via the Linux epoll API instead of polling, so onchange fires immediately on a hardware interrupt without dropping fast pulses.

const port = gpioAccess.ports.get(17);

await port.export("in", { edge: "rising", debounce: 10 });

port.onchange = (event) => {
  console.log(event.value);
};

export() accepts an optional second argument (only applied when direction is "in"):

| Option | Type | Default | Description | | ----------- | --------------------------------- | -------------- | ------------------------------------------------------------------ | | edge | "rising" \| "falling" \| "both" | "both" | Which voltage transition fires onchange. | | debounce | number | 0 (disabled) | Milliseconds of chatter (e.g. mechanical switch bounce) to ignore. | | activeLow | boolean | false | Inverts the logic level (1 when LOW, 0 when HIGH). |

Since this relies on the native epoll package, a build toolchain (e.g. build-essential and python3 on Debian/Raspberry Pi OS) is required when installing on Linux.

Document

• TSDoc

Reference

• Web GPIO API for W3C Draft

Acknowledgments

• node-web-gpio-onoff by @satakagi. This library's onchange handling is based on its epoll-based interrupt-driven approach.