Matlab function into simulink: variable declaration

Hi, I'm programming an arduino due using a matlab function into simulink. As a test, i try to let the on board let blink and count how many times the led has blinked using the matlab function with the folowing code:

function [LED,counter]= blink(pulse)
%#codegen

counter=0;
LED=0;

while true
    if pulse == 1
        LED=1;
        counter=counter+1;
    else
        LED=0;
    end
end

In this code, pulse is a pulse generator, LED goes to the pin of the on board led. With this code, the led doesn't blink because i guess the function doesn't end because of the while loop so i tried another function

function [LED,counter]= blink(pulse)
%#codegen
counter=0;
if pulse == 1
    LED=1;
    counter=counter+1;
else
    LED=0;
end

with this code, the led will blink, but the counter resets after every loop, but without 'counter=0' there is an error because counter isn't initialized. I tried with the model properties, StartFcn to initialize the counter but that doesn't work, anyone who can help me? Thanks!

Answer 1

[Walter Roberson]

Use "persistent" ? Though in that particular context I am not sure what the value would initialize to.

[Thogoe]

Thanks for the answer, but i still get the folowing error

   The PERSISTENT declaration cannot be used on function outputs.

Function 'MATLAB Function' (#36.47.57), line 3, column 1:
"persistent"
Launch diagnostic report.
Component: MATLAB Function | Category: Coder error

guess because the persistent command creates an empty matrix, so 'counter' is still undefined.

[Walter Roberson]

Do not persistent the output variable, persistent the counter variable and copy the counter variable to the output variable.