Modbus TCP read input registers moxa E1200 devices

Projects Programming
1

Hello to all,
this is my first message.

I have a problem with modbus TCP.
I have 2 moxa modules Moxa E1210 with 16 inputs and 1 Moxa E1212 with 8in and 8out.

I want to read the state of digital inputs using modbus tcp.

In the moxa manuals i've to read DI-all_statusFromDI-00,
Start Address (decimal): 0048 witch FC code 04:INPUT REGISTER and the moxa adapter replies me with 1 word data.

I tried to read al teast 1 module, but when i execute the sketch the call of requestFrom gives me the reply: invalid argument.

I've written this code:
arduino-modbus-tcp-forum.ino (2.5 KB)

Pleas help me!

Thank a lot.

2 
if (!slave.connected()) {
    slave.stop();
    slave.connect(slaveIp, slavePort);
}

You shouldn't handle the TCP connection yourself, the Modbus library should do that. Take a look at the corresponding examples!

3

Thanks for your reply!

I've always the same problem: invalid argument on the modbus request

:((((((

4

I know, my last response tells you why you have these errors.

5

I've already removed the code

if (!slave.connected()) { slave.stop(); slave.connect(slaveIp, slavePort); }

But It doesn't work fine :frowning:

6

Removing the code isn't all you have to do. You must call the corresponding code in the Modbus library.

Did you have a look at the examples of your library?

7

Hi pylon,
i've seen the example better as you tell and i resolved the problem.

What changes now if i want to add the other servers?
Can i poll in the same sketch to modbus rtu devices (having the Arduino interface)?

Thanks a lot.

8

Create one modbus client object per server.

Theoretically, yes. What Arduino board are you using? What RS485 hardware do you intend to use?

9

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