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Heat meter M-Bus through RS232

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Good day, Having spare time, so desided to play with PLC (v350). I have a heat meter on my desk. It communicates through M-Bus protocol and there are 3 ways to choose connection type: M-Bus, RS232 and CL. I think I could connect heat meter directly to PLC (without any M-bus or CL converters) with RS232 cable. The question is how to implement data exchange between those devices? Try to implement M-Bus protocol with Visio's FB protocol? Maybe someone had such a project and can share suggestions about this. Thank you!

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Hi Vidmas30,

If the device supports RS232 then you can connect it directly to the serial port of the V350.

Of course tou must set the same communication parameters for both devices. (Baud rate, start bit, parity, etc..)

Which protocol does Heat meter support?

Does M-Bus is MODBUS?

If yes then of course you can use FB MODBUS for the communication.

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  • MVP 2023

Here's a link to the M-Bus documentation-

M-Bus Doc

I gave it a quick scan. It's pretty generic and makes several references to "manufacturer specific commands". Also, the physical layer is a two-wire network that toggles between +36V and 12-24V, so I wouldn't go plugging an RS232 cable into the M-bus port.

Your best bet is to try to get some kind of communication manual that includes a description of the RS2323 protocol from the manufacturer. That should go into the detail you need.

What are the details on your heat meter?

Joe T.

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Hi, Joe, The heatmeter is made by aour local manufacturer. It comes with communication module M-bus/RS232/CL one of which is selected by jumper settings. So if I select RS232, then I can connect it directly to PLC or PC. Today I asked them what protocol goes under RS232 port (as Emil wrote). I'll write when get reply. Thank you!

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  • 1 year later...
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After two years I wonder if anybody get to develope the M-BUS protocol with the FB PROTOCOL of Unitronics.

I have some projects where the M-BUS/RS-232 converter is cheap but the M-BUS/modbus is very expensive.

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