modbus rtu communication

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Ajay Soni
Ajay Soni on 24 Feb 2011
Commented: Eric Wetjen on 15 Mar 2022
hi, i want to know that is it possible to connect the matlab with a plc using modbus rtu protocol using m-code if yes then how can we do it and how can i get the proper format of the sending data to plc.
please help me.
  2 Comments
Eric Wetjen
Eric Wetjen on 15 Mar 2022
In R2022a, Modbus RTU support is now available in the new Industrial Communication Toolbox.

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Answers (6)

Gustavo Dacanal
Gustavo Dacanal on 9 Sep 2016
Here is my code to Modbus RTU DataLogging. It works for me for a heater controller. (model NOVUS N1100). tks -Gustavo
instrreset;
clear all;
close all;
clc;
% remove any remaining serial objects to prevent serial issues
disp('BEGIN PROGRAM');
% Initialize Serial Port Object [s]
s = serial('COM3');
% Specify connection parameters
set(s,'BaudRate',9600,'DataBits',8,'StopBits',1,'Parity','None','Timeout',1);
%Open serial connection
fopen(s);
% Specify Terminator - not used for binary mode (RTU) writing
s.terminator = 'CR/LF';
% Set read mode
set(s,'readasyncmode','continuous');
%Check Open serial connection
s.Status
% RUN and COPY hexadecimal array from SimplyModbus software as example
% SimplyModbus IN [01 03 00 00 00 03 05 CB]
% Observe the output as result from SimplyModbus software
% SimplyModbus OUT [01 03 06 01 90 01 16 00 00 00 81]
request = uint8(hex2dec(['01'; '03'; '00'; '00'; '00'; '03'; '05'; 'CB']));
fwrite(s, request); %start in dec
outdec = fread(s);
outhex = dec2hex(outdec);
outstr = reshape(outhex.',1,[]); %return line string of array hexadecimal e.g.: '010306019000EB0000908D'
SP = hex2dec(outstr(7:10))*0.1 %Variable SetPoint de controler
PV = hex2dec(outstr(11:14))*0.1 %Real temperature PV
MV = hex2dec(outstr(15:18))*0.1 %Variable MV
fclose(s);
delete(s);
clear s
disp('STOP')

Robert Garnett
Robert Garnett on 8 Dec 2012
Hi Steve,
It is possible and easy. The modbus spec is well described on the modbus.org site. I have written C Simulink functions for xPC and also a matlab m code system which runs in an M code gui.
I wrote the code for a power meter and also interfaced it with an ARM 7 processor which simulated a boiler cleaning water cannons. I wrote a interrupt driven program for the ARM which was mostly C with a little bit of assembler. I used the simulink coder (then the RTW) to generate the functionality of the cannons. It worked very well.
The S functions were the hardest to write because I was doing it for the xPC platform which doesn't have a debugger. S functions aren't the easiest things to understand, but once you get to grips with them by looking at the many examples available they are very doable.
I haven't bothered writing a modbus ASCII interface because it is limited and the RTU version with appropriate data formating will handle ascii characters anyway.
I can send you copies if you like.
My email addresses are:
rob.garnett@gdfsuezau.com
rjg@wideband.net.au
Regards
Rob

Steven Edmund
Steven Edmund on 7 Mar 2011
I believe it should be possible to use the RTU protocol, however it will take a significant re-work of the code that you are referencing. modbus.org has some good resources for this, the best I found was this PDF. http://www.modbus.org/docs/PI_MBUS_300.pdf The primary thing with RTU is that you will have to change the coding and byte construction, the framing of the message and the checksum from an LRC to a CRC. Best of luck, -Steve

W.
W. on 4 Apr 2012
Greetings,
I know this is an old post, but if you are still having problems, see my posing File ID: #36022. I used RTU to communicate with a power meter.

Raimundas Steponavicius
Raimundas Steponavicius on 3 Mar 2017
Does anybody know how to implement MODBUS ASCII or RTU communication with MATLAB on the slave computer. I cannot find anything on that ! All cases (posts) that I found are when MATLAB is used as the host/master. Any info or references would be appreciated a lot.

Dogukan Kucukler
Dogukan Kucukler on 27 Jun 2018
Hello friends,
I am currently looking for a solution how to implement slave device to Industrial Control Toolbox on MATLAB by using MODBUS RTU Protocol (RS485).Is there anyone that can help me about it ? Is there any tutorial or pdf to understand these process completely ?
Thank you, DK
  1 Comment
Shumin Jiang
Shumin Jiang on 30 Sep 2018
HEY dude, have you done this? now I am in the exactly same situation as you are. Do you have have any tutorial or any other demos to understand this process? Many thanks!

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