modbus rtu communication

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.

i am using this code but it is not working http://www.mathworks.com/matlabcentral/fileexchange/27815-modbus-rs232-ascii-communication-functions

please help me.

[Eric Wetjen]

MODBUS RTU support was added to Instrument Control Toolbox in R2017a. See this resource page for details.

[Eric Wetjen]

In R2022a, Modbus RTU support is now available in the new Industrial Communication Toolbox.

Answer 1

[Gustavo Dacanal]

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')

Answer 2

[Robert Garnett]

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:

 [e-mail] 
 [e-mail]

Regards

Rob

Answer 3

[Steven Edmund]

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

Answer 4

[W.]

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.

Answer 5

[Raimundas Steponavicius]

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.

Answer 6

[Dogukan Kucukler]

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

[Shumin Jiang]

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!