GPIO

General-purpose input/output (GPIO) is a generic pin on an integrated circuit whose behavior—including whether it is an input or output pin—is controllable by the user at run time.

Using a GPIO Interface in Driver

Configuring `driver.json`

To use a GPIO interface in a driver, you need to have an input with type "gpio" in the driver.json:

{
    "models": [],
    "inputs": {
        "gpio-in": {
            "type": "gpio",
            "args": {
                "direction": "in",
                "edge": "both"
            }
        },
        "gpio-out": {
            "type": "gpio",
            "args": {
                "direction": "out",
                "level": "low"
            }
        }
    }
}

In the JSON configuration above, "gpio-in" and "gpio-out" are just names of the GPIO interfaces (you can change them to something else if you want to),
which will be used as the key to get the interface instances in the driver.
And the "type": "gpio" informs Ruff framework to distribute an GPIO interface instead of others.

Arguments

`direction`

The direction of the interface, could either be "in" or "out".

`edge`

The edge of the interface that controls interrupt events, could be one of "none", "rising", "falling" or "both".
This argument takes effect only if direction is set to "in".

An interrupt event will only be emitted if one of the conditions is matched:

The electrical level rose from low to high and the edge is set to "rising" or "both".
The electrical level fell from high to low and the edge is set to "falling" or "both".

`level`

The initial electrical level of the interface, could be either "low" or "high".
This argument takes effect only if direction is set to "out".

Writing a Driver

'use strict';

var driver = require('ruff-driver');
var gpio = require('gpio');

var Level = gpio.Level;
var Direction = gpio.Direction;
var Edge = gpio.Edge;

module.exports = driver({
    attach: function (inputs) {
        this._gpioIn = inputs['gpio-in'];
        this._gpioOut = inputs['gpio-out'];

        this._gpioIn.on('interrupt', function (value) {
            console.log('interrupt', value);
        });
    },
    exports: {
        turnOn: function (callback) {
            this._gpioOut.write(Level.high, callback);
        },
        turnOff: function (callback) {
            this._gpioOut.write(Level.low, callback);
        }
    }
});