Custum level-2 MATLAB S-function problem with desktop real-time simulink

Hi,

I try to develop a real-time simulink model to stream data to workspace of MATLAB from delsys trigno EMG system. I made a model that works perfectly when I simulate the model by using a custum level-2 MATLAB S-function to communicate with delsys Trigo and get the data. But as I need the model to run in real-time, I build the model using Simulink desktop real-time. The time steps of my custum level-2 MATLAB S-function is set up to 0.05s and I use a Unbuffer blocks to obtain the original frequency sampling at 2000Hz, (or 0.0005s time steps).

When I run in real-time my model, I do not receive any error message but EMG data are replace by 0 values. After adding some disp to my code, I notice that the model do not use anymore the function 'Outputs' of my custum level-2 MATLAB S-function. Then, the model do not ask anymore for EMG data but simply return 0 value instead.

Here my custum level-2 MATLAB S-function :

function DelsysTrignoSamplerBuffer(block)
%   The function that implements the 
%   Sampling block in simulink. This functions is a Matlab Level 2 S-function.
tcpipCommand = NaN;
tcpipEMG = NaN;
is_started = false;
rateAdjustedEmgBytesToRead = 0;
buffer = [];
at_frame_buffer = 1;
parameters = struct();
setup(block);

    function setup(block)
        % Register the number of ports.
        block.NumInputPorts  = 0;
        block.NumOutputPorts = 1;
        block.NumContStates = 0;
        block.NumDworks = 0;
        % Set output ports
        block.SetPreCompOutPortInfoToDynamic();
        block.OutputPort(1).Dimensions = [100 16];
        block.OutputPort(1).SamplingMode = 'Frame';
        
        % Number of parameters
        block.NumDialogPrms = 1;
        % Block time steps
        block.SampleTimes = [0.05 0];
        % run block in interpreted mode even w/ Acceleration
        block.SetAccelRunOnTLC(false);
        block.SimStateCompliance = 'DefaultSimState';
        block.RegBlockMethod('CheckParameters', @checkParameters);
        block.RegBlockMethod('Start', @Start); 
        block.RegBlockMethod('Outputs', @Outputs);
        block.RegBlockMethod('Terminate', @Terminate);
    end
    function checkParameters(block)
        parameters.ipAddress = block.DialogPrm(1).Data;
    end
% 
    function Start(block)
        % This function is called once, when the simulation is started.
        % Création d'une connexion TCP/IP
        tcpipCommand = tcpclient(parameters.ipAddress, 50040);
        tcpipEMG = tcpclient(parameters.ipAddress, 50041);
        %Setup interface object to read chunks of data
        rateAdjustedEmgBytesToRead=100*16;
        
        writeline(tcpipCommand,sprintf('START\r\n\r'))
        is_started = true;
        bytesReady = tcpipEMG.NumBytesAvailable;
        bytesReady = bytesReady - mod(bytesReady, rateAdjustedEmgBytesToRead);
        while bytesReady == 0
            bytesReady = tcpipEMG.NumBytesAvailable;
            bytesReady = bytesReady - mod(bytesReady, rateAdjustedEmgBytesToRead);
        end
        data = read(tcpipEMG,bytesReady,'single');
        buffer = double(reshape(data,16,[])');
        at_frame_buffer = 1;
        disp('okstart')
    end
    function Outputs(block)
        disp('okoutput')
        if size(buffer, 2) < at_frame_buffer
            bytesReady = tcpipEMG.NumBytesAvailable;
            bytesReady = bytesReady - mod(bytesReady, rateAdjustedEmgBytesToRead);
            while bytesReady == 0
                bytesReady = tcpipEMG.NumBytesAvailable;
                bytesReady = bytesReady - mod(bytesReady, rateAdjustedEmgBytesToRead);
            end
            data = read(tcpipEMG,bytesReady,'single');
            buffer = double(reshape(data,16,[])');
            at_frame_buffer = 1;
        end
        block.OutputPort(1).Data = buffer(at_frame_buffer:at_frame_buffer+99,:);
        at_frame_buffer = at_frame_buffer + 100;
    end
    function Terminate(block)
        % Cleans up the TMSi library.
        writeline(tcpipCommand,sprintf('STOP\r\n\r'))
        flush(tcpipEMG)
        is_started = false;
    end
end

How can I resolve this and have the function Outputs block works even with desktop real-time ?

Answer 1

[Jan Houska]

Hi Julien,

Level-2 MATLAB S-functions do not generate C code, and therefore cannot be used by Simulink Desktop Real-Time in Run In Kernel mode. You have two options. Either you can run the model in Connected IO mode, where the S-function will be run as-is without compilation. There's a good chance it will work if you sample rate is 20 Hz. Or, you can re-implement the TCP/IP communication using the Packet Input and Packet Output blocks and the TCP/IP protocol driver. This way, C code will be generated and you will be able to run in Run In Kernel mode.

Good Luck, Jan

[Julien ROSSATO]

Thank you for your help,

Julien