sending data from raspberry pi (python) to matlab or simulink over TCP/IP

Hello, I am trying to send random-data from raspberry pi (python script) to Matlab or simulink. The objective is to monitor the real time data from raspberry pi in simulink or matlab.

1) I have used !ping in matlab to connect raspberry pi

2) I wanted to use TCP/IP connection but i can't receive the data this is my code in raspberry pi :

import socket

import numpy as np

import encodings

from time import sleep

import random

#import json

from random import uniform

import datetime

connflag = True

HOST = '192.168.0.128' # Standard loopback interface address (localhost)

PORT = 46384 # Port to listen on (non-privileged ports are > 1023)

def my_server():

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:

print("Server Started waiting for client to connect ")

s.bind((HOST, PORT))

s.listen(5)

conn, addr = s.accept()

with conn:

print('Connected by', addr)

while True:

sleep(5)

if connflag == True:

timestamp = datetime.datetime.now()

tempreading = uniform(20.0,25.0) # Generating Temperature Readings

message = '{"timestamp":'+'"'+str(timestamp)+'",'+'"temperature":'+str(tempreading)+'}'

print("msg sent: temperature " + "%.2f" % tempreading ) # Print sent temperature msg on console

try:

s.sendall(message.encode())

except BrokenPipeError:

print("Error: Connection to the remote end has been lost") # Handle the error as needed

else:

print("waiting for connection...")

if __name__ == '__main__':

while 1:

my_server()

3) For matlab to receive the data, i used this code but it seems that it doesn't work well.

% Define the host and port information

HOST = '192.168.0.128';

PORT = 46384;

% Define the process_data_from_server function

function [x_temperature, y_humidity] = process_data_from_server(data)

parts = strsplit(data, ",");

x_temperature = parts{1};

y_humidity = parts{2};

end

% Define the my_client function

function my_client()

t = timer('TimerFcn', 'my_client', 'Period', 11, 'ExecutionMode', 'fixedRate');

start(t);

% Create a TCP socket

s = tcpip(HOST, PORT, 'NetworkRole', 'Client');

% Open the socket connection

fopen(s);

% Send the input command to the server

my = input("Enter command ");

fwrite(s, my, 'char');

% Receive the data from the server

data = fread(s, s.BytesAvailable, 'char');

data = char(data');

% Process the data and print the results

[x_temperature, y_humidity] = process_data_from_server(data);

fprintf("Temperature %s\n", x_temperature);

fprintf("Humidity %s\n", y_humidity);

% Close the socket connection

fclose(s);

stop(t);

delete(t);

pause(5);

end

% Call the my_client function in a loop

while 1

my_client();

end

I think there is a problem with matlab code because i'm not good in matlab i don't know how to change it to be able to get the data from raspberry pi.

Thank you for your help ;)

Answer 1

[Smit]

Hi,

I understand your server program is running on Raspberry Pi and client program is running on MATLAB and you are facing issues with your code.

Looking at your code, I think you will have to make multiple changes which are as follows: -

1) You say that you are connecting to Raspberry Pi using the “!ping” command in MATLAB.

However, “!” before a command implies that the OS is going to run the command. Secondly, “ping” is used to test connections and not actually make connections.

2) In the section of the code

% Receive the data from the server
data = fread(s, s.BytesAvailable, 'char');
% In the following line you have a stray single quote at the end
data = char(data');

You need to remove the stray single quote.

3) You need to pass “HOST” and “PORT” to the function. You can do so in the following manner

function my_client(HOST, PORT)

You will have to call the function with these arguments as well

my_client(HOST, PORT);

4) In MATLAB scripts, your function definitions should reside at the end. So, you will need to move the following section of the code

% Call the my_client function in a loop
while 1      
    my_client();  
end

Before the function definition.

Hope this helps!

[Fatemeh]

Thank you I changed my code as you said and also there was a problem between the data type transfered from Raspberry pi to Matlab so after i did the correction, it worked.;)

[AdiKaba]

Hello Fatemh,

I am doing simiar. Do I mind posting the MATLAB portion of the code that worked for you.

Thank you!