ElkoEP Web Service Client for OpenHAB

A small WS Client that listens to changes on ElkoEP Control Unit (e.g. eLAN-RF-003) and sends updates to OpenHAB server.

Update: code available at https://github.com/kubovy/elko-ws-client

Update: as of ELAN-RF-v3.0.096 there is a new authentication layer breaking this bridge. Do not upgrade your ELAN-RF if you want this bridge to continue working.

Update: Please checkout the Github sources, the code in this article is obsolete and will not work with new ELAN firmwares.

Requirements: NodeJS, NPM

I am using ElkoEP (https://www.elkoep.com/) as part of my home automation system. The devices such as lights, switches are controlled using a wireless controller (eLAN-RF-003). This controller has also a REST interface so integration with OpenHAB was pretty straight forward. When I was controlling everything with computers, smartphones, etc using the web interface or mobile app everything was fine. But after a short while I wanted a seamless experience with normal switches. ElkoEP offers such for their products but those switches control the device directly going around the central unit.

The first solution was to poll directly from OpenHAB with a short repeat interval and update the states of the devices. This was feasible for c.a. 3 device. First problem is that the small controller and the embedded web server apparently does not handle multiple requests very well so when a status is polled the controlling a device is not reliable. And second problem was that the updates were causing a race condition time to time causing all sorts of glitches. The second problem could be solved with locking inside the OpenHAB rules but it made the first problem worse.

After a while and little bit of reverse engineering of the eLAN-RF-003 i found out that there is also a ws:// service. This pushes ids of device after status change.

The WS Client does following:

• checks the state of changed devices provided by the web service,
• transforms the Elko format to the OpenHAB format,
• check if the state on OpenHAB server is different (preventing sending a command twice), and
• if states are different send the appropriate command to the OpenHAB server.

Currently only Switches, Dimmers and Color Items are supported by both sides. But as the code is tiny and simple extension should not be a problem.

const WebSocket = require('ws');
const axios = require("axios");
const fs = require('fs');
const JSONPath = require('advanced-json-path');
const DEBUG = false;

console.log("Starting...");

let config = JSON.parse(fs.readFileSync('config.json', 'utf8'));
if (DEBUG) console.log(config);

function RGB2HSV(json) {
    red = json.red;
    green = json.green
    blue = json.blue
    brightness = json.brightness
    var max = Math.max(red, green, blue),
        min = Math.min(red, green, blue),
        d = max - min,
        hue,
        saturation = (max === 0 ? 0 : d / max),
        value = max / 255;

    switch (max) {
        case min: hue = 0; break;
        case red: hue = (green - blue) + d * (green < blue ? 6: 0); hue /= 6 * d; break;
        case green: hue = (blue - red) + d * 2; hue /= 6 * d; break;
        case blue: hue = (red - green) + d * 4; hue /= 6 * d; break;
    }

    var hsv = {
        hue: hue * 360,
        saturation: saturation * 100,
        value: brightness * 100 / 255 // was value
    };
    
    return parseInt(hsv.hue) + ',' + parseInt(hsv.saturation) + ',' + parseInt(hsv.value);
}

/*
 * HTTP Server
 */
function getUrl(deviceDefinition, which) {
	let request = deviceDefinition[which];
	return request.url.replace("{id}", deviceDefinition.id).replace("{item}", deviceDefinition.item);
}

function axiosRequest(deviceDefinition, which, data) {
	let request = deviceDefinition[which];
	let config = {
		method: request.method.toLocaleLowerCase(),
		url: getUrl(deviceDefinition, which),
		headers: request.headers
	};
	if (data) config.data = data
        if (DEBUG) console.log("Axios: " + JSON.stringify(config));
	return axios.request(config);
}

function getResult(request, response) {
	let result;
	if (request.path) {
            result = JSONPath(response.data, request.path);
            if (DEBUG) console.log("Mapping: '" + JSON.stringify(response.data) + "' with '" + request.path + "' to '" + result + "'");
        }
	else result = response.data;
	return result;
}

function logRequest(prefix, deviceDefinition, which, response) {
	let request = deviceDefinition[which];
	let result = getResult(request, response);
	console.log(prefix, request.method + " " + getUrl(deviceDefinition, which), response.status + " " + response.statusText, result);
}

function update(deviceDefinition, state) {
	axiosRequest(deviceDefinition, 'update', state).then(function(response) {
		logRequest("Updated", deviceDefinition, 'update', response);
	});
}

function check(deviceDefinition, state) {
	let request = deviceDefinition.check
	if (request) {
		axiosRequest(deviceDefinition, 'check').then(function(response) {
			let result = getResult(request, response)
			logRequest("Checked:", deviceDefinition, 'check', response);
			if (state != result) update(deviceDefinition, state);
		});
	} else {
		update(deviceDefinition, state);
	}
}

function process(deviceDefinition) {
	axiosRequest(deviceDefinition, 'get').then(function(response) {
		let request = deviceDefinition.get
		let result = getResult(request, response);
                if (DEBUG) console.log("Transfoming: let state=" + JSON.stringify(result) + ";" + deviceDefinition.transform + ';');
                let state;
                try {
                    state = eval("let state=" + JSON.stringify(result) + ";" + deviceDefinition.transform + ';');
                } catch (e) {
                    console.log(e)
                }
                if (DEBUG) console.log("Transformation result: '" + state + "'");
		logRequest("Processed:", deviceDefinition, 'get', response);
		check(deviceDefinition, state);
	});
}

var ws = new WebSocket(config['ws']);

ws.on('open', function open() {
	console.log('connected');
});

ws.on('close', function close() {
	console.log('disconnected');
});

ws.on('message', function incoming(data) {
	console.log("Incoming:", data);
	let pattern = RegExp(config['regex']);
	let matches = pattern.exec(data);
	if (matches.length > 1) {
		let deviceId = matches[1];
		let deviceDefinition = config.devices[deviceId];
                if (deviceDefinition) {
                    deviceDefinition.id = deviceId;
                    process(deviceDefinition);
                } else {
                    console.log("Device with the ID " + deviceId + " is not defined!");
                }
	}
});

To install dependencies run $ npm install

To start the client run $ node elko-ws-client.js<