direction: Use constants vs Strings

Aligned to IoT.js's GPIO API

Change-Id: I430dd3c0ea141e2b677826f61d7069f7a4f66750
Signed-off-by: Philippe Coval <p.coval@samsung.com>

README.md

@@ -47,7 +47,7 @@ var gpio = require("gpio");
 var gpio4 = gpio.export(4, {
    // When you export a pin, the default direction is out. This allows you to set
    // the pin value to either LOW or HIGH (3.3V) from your program.
-   direction: 'out',
+   direction: gpio.DIRECTION.OUT,
 
    // set the time interval (ms) between each read when watching for value changes
    // note: this is default to 100, setting value too low will cause high CPU usage
@@ -61,13 +61,13 @@ var gpio4 = gpio.export(4, {
 });
 ```
 
-### Header direction "in"
+### Header direction IN
 
 If you plan to set the header voltage externally, use direction `in` and read value from your program.
 ```js
 var gpio = require("gpio");
 var gpio4 = gpio.export(4, {
-   direction: "in",
+   direction: gpio.DIRECTION.IN,
    ready: function() {
    }
 });
@@ -120,8 +120,8 @@ gpio4.removeListener("change", processPin4);
 gpio4.removeAllListeners("change");
 
 // you can also manually change the direction anytime after instantiation            
-gpio4.setDirection("out");
-gpio4.setDirection("in");
+gpio4.setDirection(gpio.DIRECTION.OUT);
+gpio4.setDirection(gpio.DIRECTION.IN);
 ```
 
 ## Example

lib/gpio.js

@@ -5,10 +5,12 @@ var EventEmitter = require('events').EventEmitter;
 var exists = fs.existsSync || path.exists;
 
 var gpiopath = '/sys/class/gpio/';
+var DIRECTION = { 'IN': 'in', 'OUT': 'out' };
 
 var logError = function(e) { if(e) console.log(e.code, e.action, e.path); };
 var logMessage = function() { if (exports.logging) console.log.apply(console, arguments); };
 
+
 var _write = function(str, file, fn, override) {
 	if(typeof fn !== "function") fn = logError;
 	fs.writeFile(file, str, function(err) {
@@ -111,7 +113,7 @@ var GPIO = function(headerNum, opts) {
 	this.export(function() {
 		var onSuccess = function() {
 			self.setDirection(dir, function () {
-				if ( dir === "out") {
+				if ( dir === DIRECTION.OUT) {
 					if(typeof opts.ready === 'function') opts.ready.call(self);
 				} else {
 					self.value = undefined;
@@ -157,20 +159,20 @@ GPIO.prototype.unexport = function(fn) {
 
 
 /**
- * Sets direction, default is "out"
+ * Sets direction, default is OUT
  */
 GPIO.prototype.setDirection = function(dir, fn) {
 	var self = this, path = this.PATH.DIRECTION;
-	if(typeof dir !== "string" || dir !== "in") dir = "out";
+	if(typeof dir !== "string" || dir !== DIRECTION.IN) dir = DIRECTION.OUT;
 	this.direction = dir;
 
 	logMessage('Setting direction "' + dir + '" on gpio' + this.headerNum);
 
 	function watch () {
-		if(dir === 'in') {
+		if(dir === DIRECTION.IN) {
 			if (!self.valueWatcher) {
-				// watch for value changes only for direction "in"
-				// since we manually trigger event for "out" direction when setting value
+				// watch for value changes only for direction IN
+				// since we manually trigger event for OUT direction when setting value
 				self.valueWatcher = new FileWatcher(self.PATH.VALUE, self.interval, function(val) {
 					val = parseInt(val, 10);
 					self.value = val;
@@ -179,7 +181,7 @@ GPIO.prototype.setDirection = function(dir, fn) {
 				});
 			}
 		} else {
-			// if direction is "out", try to clear the valueWatcher
+			// if direction is OUT, try to clear the valueWatcher
 			if(self.valueWatcher) {
 				self.valueWatcher.stop();
 				self.valueWatcher = null;
@@ -212,7 +214,7 @@ GPIO.prototype.setDirection = function(dir, fn) {
 GPIO.prototype._get = function(fn) {
 	var self = this, currVal = this.value;
 
-	if(this.direction === 'out') return currVal;
+	if(this.direction === DIRECTION.OUT) return currVal;
 
 	_read(this.PATH.VALUE, function(val) {
 		val = parseInt(val, 10);
@@ -234,7 +236,7 @@ GPIO.prototype.set = function(v, fn) {
 
 	// if direction is out, just emit change event since we can reliably predict
 	// if the value has changed; we don't have to rely on watching a file
-	if(this.direction === 'out') {
+	if(this.direction === DIRECTION.OUT) {
 		if(this.value !== v) {
 			_write(v, this.PATH.VALUE, function() {
 				self.value = v;
@@ -251,5 +253,6 @@ GPIO.prototype.reset = function(fn) { this.set(0, fn); };
 
 exports.logging = false;
 exports.export = function(headerNum, direction) { return new GPIO(headerNum, direction); };
+exports.DIRECTION = DIRECTION;
 exports.unexport = _unexport;
 

test/tests.js

@@ -20,7 +20,7 @@ describe('GPIO', function() {
 
 	before(function(done) {
 		gpio4 = gpio.export(4, {
-			direction: 'out',
+			direction: gpio.DIRECTION.OUT,
 			ready: done
 		});
 	});
@@ -34,7 +34,7 @@ describe('GPIO', function() {
 		describe('initializing', function() {
 			it('should open specified header', function(done) {
 				read('/sys/class/gpio/gpio4/direction', function(val) {
-					assert.equal(rmws(val), 'out');
+					assert.equal(rmws(val), gpio.DIRECTION.OUT);
 					done();
 				});
 			});
@@ -81,15 +81,15 @@ describe('GPIO', function() {
 	});
 
 	// For these tests, make sure header 4 is connected to header 25
-	// header 25 is exported with direction "out" and header 4 is used
+	// header 25 is exported with direction OUT and header 4 is used
 	// to simulate a hardware interrupt
 	describe('Header Direction In', function() {
 
 		var gpio25;
 
 		before(function(done) {
 			gpio25 = gpio.export(25, {
-				direction: 'in',
+				direction: gpio.DIRECTION.IN,
 				ready: done
 			});
 		});