"Multiply" transformation?

Setup, Configuration and Use Items & Sitemaps
1

Hello everyone!
I’ve got a ModBus-connected energy meter and trying to set it up. According to the documentation, raw values from registers must be multiplied by a given constant (constants differ for different kinds of values). Is there a simple way to set this up, or do i have to use Javascript transformation and code my multiplications by hands ?

2

You need to use javascript transformation as far as I know… Thats how I´m doing it:

thing setup:

// SMA Inverter Yield
	Bridge poller Yield                [ start=30517, length=16, refresh=5000, type="input" ] {
	    
               Thing data Day_Yield        [ readStart="30517", readValueType="int64", readTransform="JS(divide1000.js)" ]
               Thing data Total_Yield      [ readStart="30529", readValueType="int32", readTransform="JS(divide1000.js)" ]
   
   	 }

script for divide in the above thing

// Wrap everything in a function
(function(i) {
    return parseFloat(i) / 1000;
})(input)
// input variable contains data passed by openhab

Script if you want to multiply:

// Wrap everything in a function
(function(i) {
    return Math.round(parseFloat(i, 10) * 1000);
})(input)
// input variable contains data passed by openhab
3

Well, that’s what i did. So far not only i need it. Should the “Coefficient” transformation be added to OpenHAB 3 ?

4

I have no idea of OH3