I am using RPi 4 w/ OH v3.3.0 and I am looking for to connect this modbus to my OH system.
Now, I saw that I could use something like this to connect to a USB and then work with the information by receiving and sending.
Question is: how would I do this in OH?
I’ve seen there is a binding for Modbus, which is great. But is it as straight forward as simply put the COM port from the USB (which in Linux is something like /dev/ttyACM0, right?) and that’s it? Or should I do any other complex configurations that are needed in order for OH to be able to communicate with this USB device?
I’m sorry if I look too noob asking for this, working with Modbus is a completely new field for me.
There are several flavours of Modbus, different carrier technologies. Your target device is using the common RS485 wired serial bus.
To talk to that from any server, you need a RS485 serial port. Typically that would be a “USB stick” as you suggest - good choice getting one with twinkly LEDs, for confidence. And a length of twisted-pair cable of course - most use ethernet cat5 or similar.
Modbus is by nature old-fashioned and simplistic (it’s a dinosaur that still works effectively) so you will find yourself having to configure a fair amount of stuff manually.
No, it means you will have to set up Things and channels using numeric addressing.
You can’t ask for “room temperature”, for example.
You need to do something like read register type 4 at address 9756 and treat the 32-bit result as a floating point number. No coding, those are just options to set in a Thing. The binding does the work and you end up with something in a Number Item.
But you cannot guess stuff like “9756”, you must get the requirement from the makers manual.
It doesn’t cost anything at this stage to see if you can work out something like “I need to read registers 92 to 99 in order to get the important HVAC readings” from maker’s info.
I will ask for help to some engineer from Samsung, in these cases it seems suppliers have contacts that they can use to give support with these configurations.
Anyway, I will update this post later on to help future visitors with more details - as I usually like to do.
