node-red-nodes/hardware/mcp3008/pimcp3008.js

/**
 * Copyright 2016 IBM Corp.
 *
 * 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.
 **/

module.exports = function(RED) {
    "use strict";
    var fs = require('fs');
    // unlikely if not on a Pi
    try { fs.statSync("/dev/ttyAMA0"); }
    catch(err) { throw "Info : Ignoring Raspberry Pi specific node"; }

    var mcpadc = require('mcp-spi-adc');
    var mcp3008 = [];

    function PiMcpNode(n) {
        RED.nodes.createNode(this,n);
        this.pin = n.pin || 0;
        this.interval = n.interval || 1000;
        var node = this;

        try {
            fs.statSync("/dev/spidev0.0");
            if (mcp3008.length === 0) {
                for (var i=0; i<8; i++) {
                    mcp3008.push(mcpadc.open(i, function (err) {
                        if (err) { node.error("Error: "+err); }
                    }));
                }
            }
            node.on("input", function(msg) {
                var pin = null;
                if (node.pin === "M") {
                    var pay = parseInt(msg.payload.toString());
                    if ((pay >= 0) && (pay <= 7)) { pin = pay; }
                    else { node.warn("Payload needs to select channel 0 to 7"); }
                }
                else { pin = parseInt(node.pin); }
                if (pin !== null) {
                    mcp3008[pin].read(function (err, reading) {
                        if (err) { node.warn("Read error: "+err); }
                        else { node.send({payload:reading.rawValue, topic:"adc/"+pin}); }
                    });
                }
            });

        }
        catch(err) {
            node.error("Error : Can't find SPI device - is SPI enabled in raspi-config ?");
        }

        node.on("close", function(done) {
            if (mcp3008.length !== 0) {
                var j=0;
                for (var i=0; i<8; i++) {
                    mcp3008[i].close(function() { j += 1; if (j === 8) {done()} });
                }
                mcp3008 = [];
            }
            else { done(); }
        });
    }

    RED.nodes.registerType("pimcp3008",PiMcpNode);
}