Add initial support for I2C using an Arduino with Firmata / firmata.j…

…s. Issue #7

examples/card_scan_i2c_firmata.js

@@ -0,0 +1,16 @@
+var pn532 = require('../src/pn532');
+var Board = require('firmata');
+
+console.log('Initializing firmata board...');
+var board = new Board('/dev/tty.usbmodem1263141', function() {
+    board.i2cConfig();
+    var rfid = new pn532.PN532(board);
+
+    console.log('Waiting for rfid ready event...');
+    rfid.on('ready', function() {
+        console.log('Listening for a tag scan...');
+        rfid.on('tag', function(tag) {
+            console.log(Date.now(), 'UID:', tag.uid);
+        });
+    });
+}); 

src/pn532.js

@@ -28,6 +28,9 @@ class PN532 extends EventEmitter {
         } else if (hal.constructor.name === 'Bus') {
             var PN532_I2C = require('./pn532_i2c');
             this.hal = new PN532_I2C(hal);
+        } else if (hal.constructor.name === 'Board') {
+            var PN532_I2C_Firmata = require('./pn532_i2c_firmata');
+            this.hal = new PN532_I2C_Firmata(hal);
         } else {
             throw new Error('Unknown hardware type: ', hal.constructor.name);
         }

src/pn532_i2c_firmata.js

@@ -0,0 +1,67 @@
+'use strict';
+var EventEmitter = require('events').EventEmitter;
+var c = require('./constants');
+var logger = require('winston').loggers.get('i2c');
+
+function sleep(time) {
+  return new Promise(resolve => setTimeout(resolve, time));
+}
+
+class PN532_I2C_Firmata extends EventEmitter {
+    constructor(board) {
+        super();
+        this.board = board;
+    }
+
+    init() {
+        logger.debug('Initializing I2C...');
+        // TODO: Allow pins to be configurable
+        const RESET_PIN = 20;
+        const IRQ_PIN = 21;
+
+        return new Promise((resolve, reject) => {
+            this.board.pinMode(IRQ_PIN, this.board.MODES.INPUT);
+            this.board.digitalRead(IRQ_PIN, value => {
+              logger.debug('IRQ', value);
+
+              // Wait for IRQ to drop low.  See 6.3.3.2 of User Guide
+              // TODO: Allow using polling instead of IRQ pin (setInterval(..., 500))?
+              if (!value) {
+                logger.debug('i2cRead')
+                this.board.i2cReadOnce(c.I2C_ADDRESS, 26, (data) => {
+                  logger.debug('Read', data);
+
+                  if (data[0] & 1) { // RDY
+                    // Ready
+                    logger.debug('RDY bit found')
+
+                    // Slice off RDY bit and convert byte array to Buffer
+                    this.emit('data', new Buffer(data.slice(1)));
+                  }
+                })
+              }
+            });
+
+            // Not sure if required.  See https://github.com/adafruit/Adafruit-PN532/blob/master/Adafruit_PN532.cpp#L223
+            this.board.pinMode(RESET_PIN, this.board.MODES.OUTPUT);
+            this.board.digitalWrite(RESET_PIN, this.board.HIGH);
+            this.board.digitalWrite(RESET_PIN, this.board.LOW);
+
+            sleep(400).then(() => {
+              this.board.digitalWrite(RESET_PIN, this.board.HIGH);
+
+              sleep(10).then(() => {
+                logger.debug('I2C initialized.');
+                resolve();
+              })
+            })
+        });
+    }
+
+    write(buffer) {
+      logger.debug('writing...', 'length', buffer.length, buffer);
+      this.board.i2cWrite(c.I2C_ADDRESS, Array.from(buffer));
+    }
+}
+
+module.exports = PN532_I2C_Firmata;