NodeRed I2C

node-red__settings.js

...

    functionGlobalContext: {
        i2c:require('i2c'),
        os:require('os'),
        fs:require('fs'),
        glob:require('glob'),
        ua:require('universal-analytics')
        // jfive:require("johnny-five"),
        // j5board:require("johnny-five").Board({repl:false})
    }
...

sht25.humidity.datalogger.js

const i2c = global.get('i2c');

const deviceAddress = 0x40;
const temperatureCommand = 0xF3;
const humidityCommand = 0xF5;

const wire = new i2c(deviceAddress, {device: '/dev/i2c-1'});

function readWire({command, readBytes}) {
    return new Promise((resolve, reject) => {
        wire.writeByte(command, () => {
            setTimeout(() => {
                wire.read(readBytes, function(err, response) {
                    resolve(response);
                });
          }, 250);
        })
    });
    
}


function getHumidity () {
    return readWire({command: humidityCommand, readBytes: 2 })
        .then(([msb, lsb]) => {
           return {
               msb, lsb,
               value: -6 + (((msb * 256 + lsb) * 125.0) / 65536.0)
           };
        });
}


getHumidity()
    .then((humidity) => {
        node.send([
            {payload: humidity, topic: 'humidity'}
        ]);
    });
    

return;

sht25.temp.datalogger.js

const i2c = global.get('i2c');

const deviceAddress = 0x40;
const temperatureCommand = 0xF3;
const humidityCommand = 0xF5;

const wire = new i2c(deviceAddress, {device: '/dev/i2c-1'});

function readWire({command, readBytes}) {
    return new Promise((resolve, reject) => {
        wire.writeByte(command, () => {
            setTimeout(() => {
                wire.read(readBytes, function(err, response) {
                    resolve(response);
                });
          }, 250);
        })
    });
    
}


function getTemperature () {
    return readWire({command: temperatureCommand, readBytes: 2 })
        .then(([msb, lsb]) => {
            return {
                msb, lsb,
                value: -46.85 + (((msb * 256 + lsb) * 175.72) / 65536.0)
            };
        });
}


getTemperature()
    .then((temperature) => {
        node.send({payload: temperature, topic: 'temperature'});
    });
    

return;