How do I implement a one-second buffer for incoming UDP data?

In my current UDP code, I receive data called "dataset" with five columns. However, I face an issue with manually specifying the array size as 6610, which is impractical for real-time applications. I need to modify the code to continuously read data for one second. For instance, while receiving data, I aim to wait for one second and then save the dataset. This should replace the static array size declaration, such as data = read(u2, 6610, "double").

clear
client_port = 10011;
clientAddress = '192.168.100.202';
% Data packets
dataset= [];
u2 = udpport("IPV4",'LocalPort',client_port);
while 1
    tic
    for i=1:5
        data = read(u2,6610,"double");
        d = data;
        if isempty(d)
            break
        end
        dataset(:,i) = d;
    end
    toc
    d=[];
    if isempty(d)
        break
    end
end

Answer 1

[Hassaan]

@Med Future Initial skeleton code. You may need to adjust as per your requirements.

clear
client_port = 10011;
clientAddress = '192.168.100.202';
% Initialize dataset
dataset = [];
u2 = udpport("IPV4", 'LocalPort', client_port);

% Continuously read data
while true
    % Start timer
    tic
    tempData = [];
    while toc < 1 % Read data for approximately one second
        % Check if data is available to avoid blocking
        if u2.NumBytesAvailable > 0
            data = read(u2, 1, "double"); % Read one sample at a time
            tempData = [tempData; data]; % Append the received data
        end
    end
    
    if ~isempty(tempData)
        % Process the tempData as required for your application
        % For example, if you expect to reshape the data, ensure that the total
        % number of elements in tempData matches your expected structure.

        % Example placeholder for reshaping data, adapt based on your actual data structure:
        % Assuming tempData is a vector that should be organized into a matrix with 5 columns
        numColumns = 5;
        numRows = floor(length(tempData) / numColumns);
        if numRows > 0
            reshapedData = reshape(tempData(1:numRows*numColumns), numRows, numColumns);
            dataset = [dataset; reshapedData]; % Append new rows to dataset
        end
    else
        % If no data was collected in the last second, decide what action to take
        % For example, you might want to break or continue based on your requirements
        % break; % Uncomment if you wish to exit the loop when no data is received
    end
end

• Continuous Reading for One Second: The inner while toc < 1 loop ensures that the code reads data for approximately one second. Adjust the 1 in toc < 1 if you need to read for a different duration.
• Reading Data One Sample at a Time: read(u2, 1, "double", 'Timeout', 1) reads one sample at a time. This is to ensure that the loop can frequently check the elapsed time (toc) and also avoids blocking if there's no data to read. Adjust the 1 in read(u2, 1, ...) if your data packets are structured differently.
• Handling Received Data: The example assumes that the received data (tempData) is a vector that needs to be reshaped into a matrix with a specific number of rows and columns. Adjust the reshaping logic (reshape function) based on the actual structure of your incoming data.

Note:

• Ensure that the total number of elements received matches the expected structure of your dataset matrix when reshaping tempData.
• Depending on your specific needs, you may want to add additional error handling, especially for cases where the number of elements in tempData does not exactly match the expected size for reshaping.

[Med Future]

@Hassaan Thanks for the solution. when i recived the data it the reshaping is incorrect. The data recivied is like the following in which four features are in single column

40569916.2300000
70.0106595346756
0.0735326819121838
24.0050000000000
3
40570271.2300000
70.0101158494277
0.0562869580462575
26.0050000000000
3

but I need this in row. as shown below. Can you please modified the code for this?

40569916.2300000 70.0106595346756 0.0735326819121838 24.0050000000000 3
40570271.2300000 70.0101158494277 0.0562869580462575 26.0050000000000 3

Answer 2

[Umar]

To address the issue of dynamically reading data for one second without specifying a fixed array size, you can implement a solution that adapts to real-time data reception. One approach is to use a timer to control the duration of data collection. Here's a detailed guide on how to modify your existing MATLAB UDP code:

clear
client_port = 10011;
clientAddress = '192.168.100.202';
dataset = [];
u2 = udpport("IPV4", 'LocalPort', client_port);
% Define the time duration for data collection (1 second)
collection_time = 1; % in seconds
start_time = tic;
while toc(start_time) < collection_time
    for i = 1:5
        data = read(u2, 6610, "double");
        d = data;
        
        if isempty(d)
            break;
        end
        
        % Append the received data to the dataset
        if size(dataset, 1) < length(d)
            dataset = [dataset; zeros(length(d) - size(dataset, 1), size(dataset, 2))];
        end
        dataset(:, i) = d;
    end
end
disp("Data collection completed for 1 second.");
disp("Dataset size: " + size(dataset));
% Further processing or saving of the dataset can be added here

In this modified code snippet:

The collection_time variable defines the duration for data collection (1 second).

The while loop continues reading data until the elapsed time exceeds the specified collection time.

The dataset dynamically adjusts its size based on the incoming data length to avoid fixed array size limitations.

After one second of data collection, you can perform additional processing or save the dataset as needed.

By incorporating this approach, you can achieve real-time data reading without the constraints of a static array size declaration, ensuring flexibility and efficiency in your UDP data reception process.

Answer 3

[Walter Roberson]

For real-time operations, you cannot (should not) use dynamic memory allocation. Dynamic memory allocation

• runs the risk of running out of memory
• takes an indeterminate amount of time to handle the memory allocation, as the code might have to search for an available block that will fit the request

In order to continuously receive data for one second without specifying a buffer size, you need dynamic memory allocation.

So... You cannot do it. Your requirements are contradictory.

You have two options:

• stop trying to run in real time, so that you have the possibility of handling out-of-memory errors and handling variable allocation time; OR
• allocate a fixed maximum buffer size.

Allocating a fixed maximum buffer size does not mean that you must read all of the data in a single chunk: rather it means that you need to keep track of the current position in the fixed-sized output buffer.

[Umar]

To achieve continuous data reception for one second without specifying a buffer size, dynamic memory allocation is essential. By dynamically allocating memory, you can receive data continuously without the constraints of a fixed array size.

Here is how you can modify your existing code to implement dynamic memory allocation for continuous data reception: clear client_port = 10011; clientAddress = '192.168.100.202'; u2 = udpport("IPV4",'LocalPort',client_port);

% Initialize variables dataset = []; start_time = tic;

while toc(start_time) < 1 % Receive data for one second for i = 1:5 data = read(u2, 6610, "double"); if isempty(data) break; end dataset = [dataset, data]; % Append data dynamically end end

% Process the received data after one second disp("Data received for one second:"); disp(dataset);

In this modified code snippet:

We use tic and toc functions to measure the elapsed time for receiving data for one second. The dataset is dynamically updated by appending the received data in each iteration. The loop continues until one second has elapsed, ensuring continuous data reception without the need for a fixed array size. By implementing dynamic memory allocation in your UDP code, you can efficiently receive data for one second without the limitations of a predefined array size, making it more suitable for real-time applications.