node-red-nodes/hardware/BBB/144-analog-in.js

/**
 * Copyright 2014 Maxwell R Hadley
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 **/

// Require main module
var RED = require(process.env.NODE_RED_HOME+"/red/red");

// Require bonescript
try {
	var bs = require("bonescript");
} catch(err) {
	require("util").log("[BBB-analog-in] Error: cannot find module 'bonescript'");
}

// The main node definition - most things happen in here
function AnalogInputNode(n) {
    // Create a RED node
    RED.nodes.createNode(this, n);

    // Store local copies of the node configuration (as defined in the .html)
    this.topic = n.topic;
    this.pin = n.pin;

	// Define 'node' to allow us to access 'this' from within callbacks (the 'var' is essential -
	// otherwise there is only one 'node' for all instances of AnalogInputNode!)
    var node = this;

	// A callback function variable seems to be more reliable than a lambda ?!
	var cbFun = function (x) {
			var msg = {};
			msg.topic = node.topic;
			msg.payload = x.value;
			if (isNaN(x.value)) {
				this.log(x.err);
			}
			node.send(msg);
		};

	// If we have a valid pin, set the input event handler to Bonescript's analogRead
	if (["P9_39", "P9_40", "P9_37", "P9_38", "P9_33", "P9_36", "P9_35"].indexOf(node.pin) >= 0) {
		node.on("input", function (msg) { bs.analogRead(node.pin, cbFun) });
	} else {
		node.error("Unconfigured input pin");
	}
}

// Register the node by name. This must be called before overriding any of the Node functions.
RED.nodes.registerType("BBB-analog-in", AnalogInputNode);

// AnalogInputNode.prototype.close = function () { };