New house and openHAB Modbus RTU project

  • Platform information:
    • Hardware: Raspberry Pi 3 B
    • OS: Linux 5.4.72-v7+
    • Java Runtime Environment:
    • openHAB version: 2.5.10-1
  • Issue of the topic: Project

So, I’m new in openHAB platform. I will build a new house and install domotic to control Lights, Window shutters, Air Conditioner, Temperature, VMC, and grass watering, etc.

My main concern on this project was the money invested versus the quality and strong high-availability of the systems. I know and almost the persons already hear about KNX and KNX solutions. This solution is very robust, with a high level of quality and availability. But I’m in Portugal :smiley: , those types of equipment are quite expensive.

So I did some research and found an identical solution, in my opinion with high quality and strong enough, it is the Modbus. This communication protocol is used in industries, so it is very strong and with a lot of years of development, It uses a cable connection between the modules, we can found devices for all types of situations and those have a reasonable price.

I found a distributor in Portugal that represents an All-In-one device, with Modbus RTU, Digital Inputs, and Coil outputs with Power 230v(10A, 20A), etc. Those devices can be mounted on DIN electrical board and connected to Raspberry Pi with a USB - RS485 adapter.

Now I’m diving on openHAB and testing the communication over Modbus with those devices, until now everything is working perfectly. :slight_smile:

I will use the following setup:

Raspberry Pi;
Modbus RTU Modules IO for Windows shutters, lights, VMC, and AQS control;
Z-Wave for temperature, humidity, and smoke detection;
Daikin Binding integration to control the AC.

# Devices communicating, receiving info from Digital Inputs and power the coils at openHAB

Keep the good platform rolling!!

I see my friend that I had a similar idea, how to replace the expensive KNX.
Would you have a moment to take a peek and suggest what and how?
I purchased several devices with this interface, including a temperature and humidity sensor, input and output modules. I was able to run the temperature and humidity sensor in openhab. But I have a problem with outputs not willing to cooperate. The devices are working because I ran them through scripts in python, but in openhab it won’t work?


sorry for the delay.

You can test and create a Binding to “Modbus poll data” and use this to write the correct address.
What is the issue? You cannot enable and disable the output?

Note some devices can have an address difference it can be +1 or -1. Sample: Device address to Enable output 1 = 101, for some reason, there is some difference and you need to use the address 100 or 102.


Out of interest, do you a link to those devices please?


Thank you for your answer.
I have already managed to start modbus.
I noticed that sometimes communication does not work and the server needs to be restarted.
Currently, I am testing temperature and humidity sensors, and a temperature controller for underfloor heating. A friend made an input module (for testing) for a modbus that I would like to use to turn on the light. The module maintains the high state at a given address until its status is read, after reading it clears the input.

Best regards.

Modbus binding should be reasonable reliable at version 2.5
It might have some improvements at latest 2.5.12, there was some serial work during the life of 2.5, so worth trying.

In practice, physically large RS485 networks require care in layout and termination for reliable operation. The binding does have error recovery, but could be overwhelmed.