read_temp_humidity.js

/* 

Uses https://github.com/noble/noble / https://github.com/abandonware/noble to read temperature and humidity from the iBeacon advertising packets from the Moat Technolgies sensor (likely a branded version of OEM iB004N by AnkhMaway / Jaalee) 

Before using, you need to get the Mac address of your beacon, and the beacon itself has to be configured to provide temp/humidity in the advertising packets (the Moat version is pre-configured this way, but the OEM may not be).

npm install @abandonware/noble
node read-th.js

*/

const noble = require('@abandonware/noble');


const DEVICE_MAC = '';
var last_ts = 0;


noble.on('stateChange', function(state) {
    console.log('on -> stateChange: ' + state);
    if (state === 'poweredOn') {
        if(DEVICE_MAC) { 
            noble.startScanning([], true); // if we are tracking a specific device, read all of their ad packets (true=allows dupes)
        } else {
            noble.startScanning();
        }
    } else {
        noble.stopScanning();
    }
});

noble.on('scanStart', function() {
    console.log('on -> scanStart');
});

noble.on('scanStop', function() {
    console.log('on -> scanStop');
});



noble.on('discover', function(peripheral) {

    // sample output
    // {"id":"470be4bf20334f6f8d87bc0922b9195d","address":"d1-c4-a7-95-ed-f0","addressType":"random","connectable":true,"advertisement":{"manufacturerData":{"type":"Buffer","data":[76,0,2,21,187,128,158,42,120,150,70,159,187,191,76,24,56,186,29,91,112,74,7,0,197,100]}},"rssi":-90,"mtu":null,"state":"disconnected"}

    if(!DEVICE_MAC) {
        console.log('on -> discover: ' + peripheral);
        return;
    } else if (peripheral.address!=DEVICE_MAC) { 
        return; 
    }
    
    if (parseInt(new Date() / 1000) - last_ts < 60) { return; } // don't print too many updates

    major = peripheral.advertisement.manufacturerData.readUInt16BE(20);
    minor = peripheral.advertisement.manufacturerData.readUInt16BE(22);

    // the Moat technologies math subtracts an additional 0.09599609375, but it's not clear this is needed according to the SHT20 datasheet (the temp/humidity chip): https://github.com/DFRobot/DFRobot_SHT20/blob/master/Sensirion-Humidity-SHT20-Datasheet.pdf
    //  t = -46.85 + (( (((major & 255) << 8) | ((minor & 49152) >> 8)) / 65536) * 175.72) - 0.09599609375;
    //  h = -6 + (125 * (major & 65280) / 65536) - 0.75; // also not sure we need to adjust the humidity value like this

    t = -46.85 + (( (((major & 255) << 8) | ((minor & 49152) >> 8)) / 65536) * 175.72);
    t_f = t * 9/5 + 32;

    h = -6 + (125 * (major & 65280) / 65536);

    console.log((new Date).toISOString() + " " + peripheral.advertisement.manufacturerData.toString('hex').replace(/(.{4})/g, '$1 ').replace(/(^\s+|\s+$)/,'') + " • t: " + Math.round(t*10,1)/10 + "C / " + Math.round(t_f*10,1)/10 + "F, h: " + Math.round(h*10,1)/10 + "%");	

    last_ts = parseInt(new Date() / 1000);

});