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rpi-gpio.js
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rpi-gpio.js
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var fs = require('fs');
var util = require('util');
var EventEmitter = require('events').EventEmitter;
var retry = require('async-retry');
var debug = require('debug')('rpi-gpio');
var Epoll = require('epoll').Epoll;
var PATH = '/sys/class/gpio';
var PINS = {
v1: {
// 1: 3.3v
// 2: 5v
'3': 0,
// 4: 5v
'5': 1,
// 6: ground
'7': 4,
'8': 14,
// 9: ground
'10': 15,
'11': 17,
'12': 18,
'13': 21,
// 14: ground
'15': 22,
'16': 23,
// 17: 3.3v
'18': 24,
'19': 10,
// 20: ground
'21': 9,
'22': 25,
'23': 11,
'24': 8,
// 25: ground
'26': 7
},
v2: {
// 1: 3.3v
// 2: 5v
'3': 2,
// 4: 5v
'5': 3,
// 6: ground
'7': 4,
'8': 14,
// 9: ground
'10': 15,
'11': 17,
'12': 18,
'13': 27,
// 14: ground
'15': 22,
'16': 23,
// 17: 3.3v
'18': 24,
'19': 10,
// 20: ground
'21': 9,
'22': 25,
'23': 11,
'24': 8,
// 25: ground
'26': 7,
// Model B+ pins
// 27: ID_SD
// 28: ID_SC
'29': 5,
// 30: ground
'31': 6,
'32': 12,
'33': 13,
// 34: ground
'35': 19,
'36': 16,
'37': 26,
'38': 20,
// 39: ground
'40': 21
}
};
var RETRY_OPTS = {
retries: 100,
minTimeout: 10,
factor: 1
}
var DIR_IN = 'in';
var DIR_OUT = 'out';
var DIR_LOW = 'low';
var DIR_HIGH = 'high';
var MODE_RPI = 'mode_rpi';
var MODE_BCM = 'mode_bcm';
var EDGE_NONE = 'none';
var EDGE_RISING = 'rising';
var EDGE_FALLING = 'falling';
var EDGE_BOTH = 'both';
function Gpio() {
var currentPins;
var currentValidBcmPins;
var exportedInputPins = {};
var exportedOutputPins = {};
var getPinForCurrentMode = getPinRpi;
var pollers = {};
this.DIR_IN = DIR_IN;
this.DIR_OUT = DIR_OUT;
this.DIR_LOW = DIR_LOW;
this.DIR_HIGH = DIR_HIGH;
this.MODE_RPI = MODE_RPI;
this.MODE_BCM = MODE_BCM;
this.EDGE_NONE = EDGE_NONE;
this.EDGE_RISING = EDGE_RISING;
this.EDGE_FALLING = EDGE_FALLING;
this.EDGE_BOTH = EDGE_BOTH;
/**
* Set pin reference mode. Defaults to 'mode_rpi'.
*
* @param {string} mode Pin reference mode, 'mode_rpi' or 'mode_bcm'
*/
this.setMode = function(mode) {
if (mode === this.MODE_RPI) {
getPinForCurrentMode = getPinRpi;
} else if (mode === this.MODE_BCM) {
getPinForCurrentMode = getPinBcm;
} else {
throw new Error('Cannot set invalid mode');
}
};
/**
* Setup a channel for use as an input or output
*
* @param {number} channel Reference to the pin in the current mode's schema
* @param {string} direction The pin direction, either 'in' or 'out'
* @param edge edge Informs the GPIO chip if it needs to generate interrupts. Either 'none', 'rising', 'falling' or 'both'. Defaults to 'none'
* @param {function} onSetup Optional callback
*/
this.setup = function(channel, direction, edge, onSetup /*err*/) {
if (arguments.length === 2 && typeof direction == 'function') {
onSetup = direction;
direction = this.DIR_OUT;
edge = this.EDGE_NONE;
} else if (arguments.length === 3 && typeof edge == 'function') {
onSetup = edge;
edge = this.EDGE_NONE;
}
channel = parseInt(channel)
direction = direction || this.DIR_OUT;
edge = edge || this.EDGE_NONE;
onSetup = onSetup || function() {};
if (typeof channel !== 'number') {
return process.nextTick(function() {
onSetup(new Error('Channel must be a number'));
});
}
if (direction !== this.DIR_IN &&
direction !== this.DIR_OUT &&
direction !== this.DIR_LOW &&
direction !== this.DIR_HIGH
) {
return process.nextTick(function() {
onSetup(new Error('Cannot set invalid direction'));
});
}
if ([
this.EDGE_NONE,
this.EDGE_RISING,
this.EDGE_FALLING,
this.EDGE_BOTH
].indexOf(edge) == -1) {
return process.nextTick(function() {
onSetup(new Error('Cannot set invalid edge'));
});
}
var pinForSetup;
var onListen = function(readChannel) {
this.read(readChannel, function(err, value) {
if (err) {
debug(
'Error reading channel value after change, %d',
readChannel
);
return
}
debug(
'emitting change on channel %s with value %s',
readChannel,
value
);
this.emit('change', readChannel, value);
}.bind(this));
}.bind(this);
setRaspberryVersion()
.then(function() {
pinForSetup = getPinForCurrentMode(channel);
if (!pinForSetup) {
throw new Error(
'Channel ' + channel + ' does not map to a GPIO pin'
);
}
debug('set up pin %d', pinForSetup);
return isExported(pinForSetup)
})
.then(function(isExported) {
if (isExported) {
return unexportPin(pinForSetup);
}
})
.then(function() {
return exportPin(pinForSetup);
})
.then(function() {
return retry(function() {
return setEdge(pinForSetup, edge);
}, RETRY_OPTS);
})
.then(function() {
if (direction === DIR_IN) {
exportedInputPins[pinForSetup] = true;
} else {
exportedOutputPins[pinForSetup] = true;
}
return retry(function() {
return setDirection(pinForSetup, direction)
}, RETRY_OPTS);
})
.then(function() {
listen(channel, onListen);
})
.then(function() {
onSetup();
})
.catch(function(err) {
onSetup(err);
});
};
/**
* Write a value to a channel
*
* @param {number} channel The channel to write to
* @param {boolean} value If true, turns the channel on, else turns off
* @param {function} cb Optional callback
*/
this.write = this.output = function(channel, value, cb /*err*/) {
var pin = getPinForCurrentMode(channel);
cb = cb || function() {}
if (!exportedOutputPins[pin]) {
return process.nextTick(function() {
cb(new Error('Pin has not been exported for write'));
});
}
value = (!!value && value !== '0') ? '1' : '0';
debug('writing pin %d with value %s', pin, value);
fs.writeFile(PATH + '/gpio' + pin + '/value', value, cb);
};
/**
* Read a value from a channel
*
* @param {number} channel The channel to read from
* @param {function} cb Callback which receives the channel's boolean value
*/
this.read = this.input = function(channel, cb /*err,value*/) {
if (typeof cb !== 'function') {
throw new Error('A callback must be provided')
}
var pin = getPinForCurrentMode(channel);
if (!exportedInputPins[pin] && !exportedOutputPins[pin]) {
return process.nextTick(function() {
cb(new Error('Pin has not been exported'));
});
}
fs.readFile(PATH + '/gpio' + pin + '/value', 'utf-8', function(err, data) {
if (err) {
return cb(err)
}
data = (data + '').trim() || '0';
debug('read pin %s with value %s', pin, data);
return cb(null, data === '1');
});
};
/**
* Unexport any pins setup by this module
*
* @param {function} cb Optional callback
*/
this.destroy = function(cb) {
var tasks = Object.keys(exportedOutputPins)
.concat(Object.keys(exportedInputPins))
.map(function(pin) {
return new Promise(function(resolve, reject) {
removeListener(pin, pollers)
unexportPin(pin)
.then(resolve)
.catch(reject);
});
});
Promise.all(tasks)
.then(function() {
return cb();
})
.catch(function(err) {
return cb(err);
});
};
/**
* Reset the state of the module
*/
this.reset = function() {
exportedOutputPins = {};
exportedInputPins = {};
this.removeAllListeners();
currentPins = undefined;
currentValidBcmPins = undefined;
getPinForCurrentMode = getPinRpi;
pollers = {}
};
// Init
EventEmitter.call(this);
this.reset();
// Private functions requiring access to state
function setRaspberryVersion() {
if (currentPins) {
return Promise.resolve();
}
return new Promise(function(resolve, reject) {
fs.readFile('/proc/cpuinfo', 'utf8', function(err, data) {
if (err) {
return reject(err);
}
// Match the last 4 digits of the number following "Revision:"
var match = data.match(/Revision\s*:\s*[0-9a-f]*([0-9a-f]{4})/);
if (!match) {
var errorMessage = 'Unable to match Revision in /proc/cpuinfo: ' + data;
return reject(new Error(errorMessage));
}
var revisionNumber = parseInt(match[1], 16);
var pinVersion = (revisionNumber < 4) ? 'v1' : 'v2';
debug(
'seen hardware revision %d; using pin mode %s',
revisionNumber,
pinVersion
);
// Create a list of valid BCM pins for this Raspberry Pi version.
// This will be used to validate channel numbers in getPinBcm
currentValidBcmPins = []
Object.keys(PINS[pinVersion]).forEach(
function(pin) {
// Lookup the BCM pin for the RPI pin and add it to the list
currentValidBcmPins.push(PINS[pinVersion][pin]);
}
);
currentPins = PINS[pinVersion];
return resolve();
});
});
};
function getPinRpi(channel) {
return currentPins[channel] + '';
};
function getPinBcm(channel) {
channel = parseInt(channel, 10);
return currentValidBcmPins.indexOf(channel) !== -1 ? (channel + '') : null;
};
/**
* Listen for interrupts on a channel
*
* @param {number} channel The channel to watch
* @param {function} cb Callback which receives the channel's err
*/
function listen(channel, onChange) {
var pin = getPinForCurrentMode(channel);
if (!exportedInputPins[pin] && !exportedOutputPins[pin]) {
throw new Error('Channel %d has not been exported', channel);
}
debug('listen for pin %d', pin);
var poller = new Epoll(function(err, innerfd, events) {
if (err) throw err
clearInterrupt(innerfd);
onChange(channel);
});
var fd = fs.openSync(PATH + '/gpio' + pin + '/value', 'r+');
clearInterrupt(fd);
poller.add(fd, Epoll.EPOLLPRI);
// Append ready-to-use remove function
pollers[pin] = function() {
poller.remove(fd).close();
}
};
}
util.inherits(Gpio, EventEmitter);
function setEdge(pin, edge) {
debug('set edge %s on pin %d', edge.toUpperCase(), pin);
return new Promise(function(resolve, reject) {
fs.writeFile(PATH + '/gpio' + pin + '/edge', edge, function(err) {
if (err) {
return reject(err);
}
return resolve();
});
});
}
function setDirection(pin, direction) {
debug('set direction %s on pin %d', direction.toUpperCase(), pin);
return new Promise(function(resolve, reject) {
fs.writeFile(PATH + '/gpio' + pin + '/direction', direction, function(err) {
if (err) {
return reject(err);
}
return resolve();
});
});
}
function exportPin(pin) {
debug('export pin %d', pin);
return new Promise(function(resolve, reject) {
fs.writeFile(PATH + '/export', pin, function(err) {
if (err) {
return reject(err);
}
return resolve();
});
});
}
function unexportPin(pin) {
debug('unexport pin %d', pin);
return new Promise(function(resolve, reject) {
fs.writeFile(PATH + '/unexport', pin, function(err) {
if (err) {
return reject(err);
}
return resolve();
});
});
}
function isExported(pin) {
return new Promise(function(resolve, reject) {
fs.exists(PATH + '/gpio' + pin, function(exists) {
return resolve(exists);
});
});
}
function removeListener(pin, pollers) {
if (!pollers[pin]) {
return
}
debug('remove listener for pin %d', pin)
pollers[pin]()
delete pollers[pin]
}
function clearInterrupt(fd) {
fs.readSync(fd, Buffer.alloc(1), 0, 1, 0);
}
var GPIO = new Gpio();
// Promise
GPIO.promise = {
DIR_IN: DIR_IN,
DIR_OUT: DIR_OUT,
DIR_LOW: DIR_LOW,
DIR_HIGH: DIR_HIGH,
MODE_RPI: MODE_RPI,
MODE_BCM: MODE_BCM,
EDGE_NONE: EDGE_NONE,
EDGE_RISING: EDGE_RISING,
EDGE_FALLING: EDGE_FALLING,
EDGE_BOTH: EDGE_BOTH,
/**
* @see {@link Gpio.setup}
* @param channel
* @param direction
* @param edge
* @returns {Promise}
*/
setup: function (channel, direction, edge) {
return new Promise(function (resolve, reject) {
function done(error) {
if (error) return reject(error);
resolve();
}
GPIO.setup(channel, direction, edge, done)
})
},
/**
* @see {@link Gpio.write}
* @param channel
* @param value
* @returns {Promise}
*/
write: function (channel, value) {
return new Promise(function (resolve, reject) {
function done(error) {
if (error) return reject(error);
resolve();
}
GPIO.write(channel, value, done)
})
},
/**
* @see {@link Gpio.read}
* @param channel
* @returns {Promise}
*/
read: function (channel) {
return new Promise(function (resolve, reject) {
function done(error, result) {
if (error) return reject(error);
resolve(result);
}
GPIO.read(channel, done)
})
},
/**
* @see {@link Gpio.destroy}
* @returns {Promise}
*/
destroy: function () {
return new Promise(function (resolve, reject) {
function done(error) {
if (error) return reject(error);
resolve();
}
GPIO.destroy(done)
})
},
on: GPIO.on.bind(GPIO),
once: GPIO.once.bind(GPIO),
addListener: GPIO.addListener.bind(GPIO),
removeListener: GPIO.removeListener.bind(GPIO),
removeAllListeners: GPIO.removeAllListeners.bind(GPIO),
};
module.exports = GPIO;