split out GPIO stuff from https://github.com/natevw/node-nrf

.gitignore

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+.DS_Store
+node_modules/

index.js

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+var fs = require('fs'),
+    events = require('events'),
+    Epoll = require('epoll').Epoll;
+
+// c.f. https://github.com/fivdi/onoff
+
+// see "Sysfs Interface for Userspace" in
+// https://www.kernel.org/doc/Documentation/gpio.txt
+
+/*
+var pin1 = require("./gpio").connect(17),
+    pin2 = require("./gpio").connect(22);
+pin2.mode('in');
+pin1.mode('high'); pin2.value();
+pin1.mode('low'); pin2.value();
+*/
+
+exports.connect = function (pin) {        // TODO: sync up compat, split out
+    pin = +pin;
+
+    var fd,     // faster value access
+        pinPath = "/sys/class/gpio/gpio"+pin;
+    try {
+        fd = fs.openSync(pinPath+"/value",'r+');
+    } catch (e) {
+        if (e.code === 'ENOENT') {
+            // pin hasn't been exported, request and open again
+            fs.writeFileSync("/sys/class/gpio/export", ''+pin);
+            fd = fs.openSync(pinPath+"/value",'r+');
+        } else throw e;
+    }
+
+    var gpio = new events.EventEmitter();
+
+    gpio.mode = function (mode) {       // 'in','out','low','high'
+        fs.writeFileSync(pinPath+"/direction", mode);
+    };
+
+    gpio.value = function (val) {
+        var v = Buffer(1);
+        if (!arguments.length) {
+            fs.readSync(fd, v,0,1, 0);
+            return (v[0] === '1'.charCodeAt(0)) ? true : false;
+        } else {
+            v[0] = (val) ? '1'.charCodeAt(0) : '0'.charCodeAt(0);
+            fs.writeSync(fd, v,0,1, 0);
+        }
+    }
+
+    var watcher = new Epoll(function () {
+        var v = gpio.value();
+        gpio.emit((v) ? 'rise' : 'fall', v);
+        gpio.emit('both', v);
+    }), watching = false;
+    gpio.on('newListener', updateListening.bind(null, '+'));
+    gpio.on('removeListener', updateListening.bind(null, '-'));
+    function updateListening(which, name, fn) {
+        var l = {};
+        ['both', 'rise', 'fall'].forEach(function (k) {
+            var arr = gpio.listeners(k);
+            l[k[0]] = arr.length;
+            if (k === name) {           // need this because node.js doesn't specify up-to-date lists
+                var present = ~arr.indexOf(fn);
+                if (!present && '+') l[k[0]] += 1;
+                else if (present && '-') l[k[0]] -= 1;
+            }
+        });
+
+        if (l.b || (l.r && l.f)) fs.writeFileSync(pinPath+"/edge", 'both');
+        else if (l.r) fs.writeFileSync(pinPath+"/edge", 'rising');
+        else if (l.f) fs.writeFileSync(pinPath+"/edge", 'falling');
+        else fs.writeFileSync(pinPath+"/edge", 'none');
+
+        if (l.b || l.r || l.f) {
+            if (!watching) {
+                watcher.add(fd, Epoll.EPOLLPRI);
+                watching = true;
+            }
+        } else if (watching) {
+            watcher.remove(fd);
+            watching = false;
+        }
+    }
+
+    return gpio;
+}

package.json

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+{
+  "name": "pi-pins",
+  "version": "1.0.0",
+  "description": "GPIO (with interrupts) for embedded Linux machines like Raspberry Pi and BeagleBone",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/natevw/pi-pins.git"
+  },
+  "keywords": [
+    "gpio",
+    "raspi"
+  ],
+  "author": "Nathan Vander Wilt",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/natevw/pi-pins/issues"
+  },
+  "homepage": "https://github.com/natevw/pi-pins"
+}