How to store object(like udp object) in level-2 s-function?

Hello all,

I want to send control input from Matlab to FlightGear and receive aircraft data from FlightGear to Matlab with UDP communication.

So I made a code below:

function FG_Simulink(block)

% Level-2 MATLAB file S-Function for UDP communication with FlightGear

setup(block)

function setup(block)

% Register number of dialog parameters

block.NumDialogPrms = 0; % UDP send and receive ports

% Register number of input and output ports

block.NumInputPorts = 4; % aileron, elevator, rudder, throttle

block.NumOutputPorts = 11; % u, v, w, alpha, beta, p, q, r, phi, theta, psi

% Setup functional port dimensions

block.SetPreCompInpPortInfoToDynamic;

block.SetPreCompOutPortInfoToDynamic;

% Register sample times

% Specify discrete sample time with a period of 0.01 seconds and an offset of 0

block.SampleTimes = [0, 0]; % Correct format for discrete sample time

% Specify the block simStateCompliance.

block.SimStateCompliance = 'DefaultSimState';

% Register methods

block.RegBlockMethod('Start', @Start);

block.RegBlockMethod('Outputs', @Outputs);

block.RegBlockMethod('Terminate', @Terminate);

block.RegBlockMethod('SetInputPortSamplingMode', @SetInputPortSamplingMode);

block.RegBlockMethod('PostPropagationSetup', @DoPostPropSetup);

function SetInputPortSamplingMode(block, port, mode)

% Set the input port sampling mode

block.InputPort(port).SamplingMode = mode;

% Set the same sampling mode for all output ports

for i = 1:block.NumOutputPorts

block.OutputPort(i).SamplingMode = mode;

end

function DoPostPropSetup(block)

% Setup Dwork

block.NumDworks = 0;

% Setup Pwork (Pointer Work Vector) for storing UDP object

block.NumPworks = 2; % We need to store two UDP objects

function Start(block)

% Declare persistent variables to store UDP sender and receiver

persistent UdpSender UdpReceiver

% Initialize UDP sender and receiver

% Retrieve ports from dialog parameters

if isempty(UdpSender)

try

UdpSender = udpport("IPV4",'LocalPort',55001, 'Timeout', 1);

block.Pwork(1).Data = UdpSender;

catch e

error('Failed to bind sender UDP port: %s', e.message);

end

end

if isempty(UdpReceiver)

try

UdpReceiver = udpport("IPV4",'LocalPort',55002, 'Timeout', 1);

block.Pwork(2).Data = UdpReceiver;

catch e

error('Failed to bind receiver UDP port: %s', e.message);

end

end

function Outputs(block)

% Retrieve UDP objects from UserData

% Create input data vector

inputVector = zeros(1, 4);

inputVector(1) = block.InputPort(1).Data; % aileron

inputVector(2) = block.InputPort(2).Data; % elevator

inputVector(3) = block.InputPort(3).Data; % rudder

inputVector(4) = block.InputPort(4).Data; % throttle

Udpsender = block.Pwork(1).Data;

Udpreceiver = block.Pwork(2).Data;

% Send input data to FlightGear

try

write(Udpsender, inputVector, 'double', "LocalPort",55002); % Send to FlightGear receive port

catch e

warning('Failed to send data to FlightGear: %s', '%s', e.message);

end

% Receive flight data from FlightGear

try

data = read(Udpreceiver, 88, "double"); % 11 floats * 4 bytes each

if ~isempty(data)

outputVector = typecast(data, 'double');

for i = 1:block.NumOutputPorts

block.OutputPort(i).Data = outputVector(i);

end

end

catch e

% Handle timeout or any read errors

warning('Failed to receive data from FlightGear: %s', '%s', e.message);

end

function Terminate(block)

But when I launch a simulink file, the error was occured : "Cause: The property 'NumPworks' is not recognized for the class 'Simulink.MSFcnRunTimeBlock'."

I know that Dwork can not store the object type data, so if you have any idea to solve this problem, please let me know.

Thank you.

Answer 1

[Divyam]

Hi @준호,

To store the UDP packets associated with a specific Simulink block, the "UserData" parameter of the Simulink block can be utilized to store data across callbacks. For your reference, I have made the edits to the "Start" function which incorporates the desired functionality.

function Start(block)
    % Declare persistent variables to store UDP sender and receiver
    persistent UdpSender UdpReceiver
    
    %-- Get the block path --%
    blockPath = gcb(block);
    
    %-- Comment the below line if you don't wish to store the UserData persistently --%
    set_param(gcb, 'UserDataPersistent', 'on');
    
    % Initialize UDP sender and receiver
    % Retrieve ports from dialog parameters
    if isempty(UdpSender)
        try
            UdpSender = udpport("IPV4",'LocalPort',55001, 'Timeout', 1);
            %-- Setting the UserData property to store UDP object --%
            set_param(blockPath, 'UserData', UdpSender); 
        catch e
            error('Failed to bind sender UDP port: %s', e.message);
        end
    end
    if isempty(UdpReceiver)
        try
            UdpReceiver = udpport("IPV4",'LocalPort',55002, 'Timeout', 1);
            %-- Setting the UserData property to store UDP object --%
            set_param(blockPath, 'UserData', UdpReceiver);
        catch e
            error('Failed to bind receiver UDP port: %s', e.message);
        end
    end

For more information regarding the 'UserData' parameter, you can refer to this documentation: https://www.mathworks.com/help/simulink/ug/associating-user-data-with-blocks.html