S-function simulink for serial communication

[Henkjaap]

I'm trying to read data from a serial port in simulink. The serial configuration blocks and query instrument are not working properly for the device I try to read over COM port.

In matlab, I can easily read out data from the device using fopen() and fscanf().

Using the MATLAB function block in simulink, I get the same result in simulink. Problem is: it needs to open and close the serial connection every step, slowing down my system.

I'm trying to write level1 s-function to overcome this problem. Right now I have:

function [sys,x0,str,ts] = test1(t,x,u,flag)
NMEA = serial('COM2', 'BaudRate', 4800);
switch flag
case 0
[sys,x0,str,ts] = mdlInitializeSizes(NMEA);
case 3
sys = mdlOutputs(t,x,u, NMEA);
case { 1, 2, 4, 9 }
sys = [];
otherwise
error(['Unhandled flag = ',num2str(flag)]);
end;

function [sys,x0,str,ts] = mdlInitializeSizes(NMEA)
sizes = simsizes;
sizes.NumContStates= 0;
sizes.NumDiscStates= 0;
sizes.NumOutputs= 1;
sizes.NumInputs= 1;
sizes.DirFeedthrough=1;
sizes.NumSampleTimes=1;
sys = simsizes(sizes);
x0 = [];
str = [];
ts = [-1 0];
fopen(NMEA);

function sys = mdlOutputs(t,x,u,NMEA)
sys = fscanf(NMEA);

Giving me the error that the port needs to be opened at flag=3 (output). But I don't want to open the com2 every step as this will get really slow. How to solve this? I just want to open the connection once and constantly read from it (in simulink).

 

[NateD]

</code>The best solution is probably to use the MATLAB Function block in Simulink and open the serial connection outside of the Simulink model. This allows you to open the connection and keep reading from it without having to open and close it every time step. For example, you could have a MATLAB script that opens the connection and then runs the Simulink model. The Simulink model would then read the data from the serial connection using the MATLAB Function block. When the Simulink model is done running, the MATLAB script would close the connection. Alternatively, you could also use a Simulink Stateflow chart. A Stateflow chart can contain MATLAB code and can be used to control the opening and closing of the serial connection.