How to run Modbus TCP in real time using Simulink?

Question

Bartosz Soltowski 2021-8-30

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编辑： TryHarder 2023-11-22

Hi,

I have a Matlab script to communicate with my relay using Modbus TCP. The script was generated using Modbus Explorer in Matlab.

The code works well. It turns on/off my relay according to specified conditions as well as reads its status.

I am now trying to execute Matlab code from my Simulink model. I imported Matlab Function block which includes Matlab code (generated before) to control the relay. When I click Run button, I am getting error below:

Cannot write 'double' data to the buffer. The input data have to be 'uint8' type. Function 'MATLAB Function' (#24.1132.1168), line 31, column 1: "write(m, 'coils', 1000, 1, serverId)"

I tried to change names of my variables (as someone suggested that this could be the issue), I also changed all data types but I could not fix it.

I can't understand why am I getting this error if the same code executed in Matlab works fine?

I would be really grateful for your help!

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Answer 1

Bazarov 2022-7-11

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Hi,

I have the same problem. Can anybody help?

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Answer 2

Akshay Jankee 2023-2-2

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Hi Bartosz and Bazarov,

I also need to do something similar. Have you managed to sort out this issue?

Best regards,

Akshay

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Answer 3

TryHarder 2023-11-22

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https://ww2.mathworks.cn/matlabcentral/answers/1443204-how-to-run-modbus-tcp-in-real-time-using-simulink#answer_1358032

编辑：TryHarder 2023-11-22

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Hi everyone,

I have the same issue when I add a constant as an input of my function.

FWIW, the following function works nice from a MatLab function in Simulink :

function dataWrite = dataWrite
modbustype = 'tcpip';
modbusserver = '192.168.0.80';
modbusport = 502 ;
m = modbus(modbustype, modbusserver,modbusport);
write(m,'coils', 1, 1) ;
dataWrite = 1;

But with a constant as an input (activated with a button (on-off)), it did not work and I get the same error message...

function dataWrite = dataWrite(input)
modbustype = 'tcpip';
modbusserver = '192.168.0.80';
modbusport = 502 ;
value = uint8(input) % also test with double(input) or without cast in ordre to debug...
m = modbus(modbustype, modbusserver,modbusport);
write(m,'coils', 1, value) ;
dataWrite = value ; % To a display bloc