How to send commands to Modbus Router

[carlosdr02 0]

I need to send commands to a Modbus router to turn on a thermostat. I've heard that the commands need to be sent in hexadecimal format, as shown in 

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I found online:

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But how can I know how to encript the commands I want in this format, I mean, how many characters it needs to be, in what order, etc. I can't find any info online so any help is appreciated.

Thx.

Edited March 30, 2022 by carlosdr02
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[jakub.jezek 353]

1 minute ago, carlosdr02 said:

hex characters are before valueHex on this line:

Those are static value for particular register to which I write

 

That 0x00, 0x02 is message ID, that with one Modbus TCP device is not important, so I kept it static.

 

that first 0x06 is info, that you are sending data to one holding register.

 

0x01, 0x06, 0xD0 is actual register and probably something else.

 

I would suggest atleast trial version of Simply Modbus TCP client, that can give you that Modbus commads and you can see there what you can keep static and what dynamic in Fibaro.

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Also, Trial ends after several TCP commands and just by restarting the app it will renew the trial

 

Or you can use CAS Modbus scanner from

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. That one however has bug, that you cannot edit write commands to test them and always create new write command. But it is free.

[jakub.jezek 353]

2 hours ago, carlosdr02 said:

But how can I know how to encript the commands I want in this format

You need to convert decimal or string to hex. See variable valueHex in my example below

 

My example (setting setpoint for thermostat):

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[jakub.jezek 353]

3 minutes ago, carlosdr02 said:

Only site I found is 

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.

This is actually a good one.

 

We use:

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And if you want to test Modbus connection before you attempt to use it with device, you can use Modbus simulator.

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[carlosdr02 0]

17 hours ago, jakub.jezek said:

You need to convert decimal or string to hex. See variable valueHex in my example below

 

My example (setting setpoint for thermostat):

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Well that definitely helped, but I still don't understand what those hex characters are before valueHex on this line:

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[carlosdr02 0]

2 hours ago, jakub.jezek said:

Those are static value for particular register to which I write

 

That 0x00, 0x02 is message ID, that with one Modbus TCP device is not important, so I kept it static.

 

that first 0x06 is info, that you are sending data to one holding register.

 

0x01, 0x06, 0xD0 is actual register and probably something else.

 

I would suggest atleast trial version of Simply Modbus TCP client, that can give you that Modbus commads and you can see there what you can keep static and what dynamic in Fibaro.

Please login or register to see this link.

 

Also, Trial ends after several TCP commands and just by restarting the app it will renew the trial

 

Or you can use CAS Modbus scanner from

Please login or register to see this link.

. That one however has bug, that you cannot edit write commands to test them and always create new write command. But it is free.

Any documentation you could recommend me to learn about this? Because I tried a bunch of different commands with different formats and none of them seems to work. Only site I found is 

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.