send data by serial port

I want send a cell data with elements are chars through visual COM.

In trans:

    for i=1:length(f)% f is a cell array
    YourCell = {f{i}};
    string = YourCell{1};
    fprintf(s,'%c',string);
    end

In receive:

    function BytesAvailable_Callback(obj,event)
    global s;
    myData = fgets(s)

But I get error:

• Error using fgetsInvalid file identifier. Use fopen to generate a valid file identifier. *
• Error in GUIDE_RECEIVE>BytesAvailable_Callback (line 170)myData = fgets(s) *

So, How can I fix it ? Thank for your help

Answer 1

[Geoff Hayes]

Dao - how and where in your GUI have you initialized s? Based on the error message and the fact that s is declared as a global variable, it probably has not been initialized properly and so is empty. For example, the following code generates the same error message

 s = [];
 fgets(s);

Find the code where you initialize s and make sure that you specify that s is global. Something like

 function opensSerialPort()

 global s;

 s = fopen(...);

Now try the re-running your GUI to see what happens.

---------------

As an aside, you may want to experiment with the input obj to your BytesAvailable_Callback. As obj is the serial port object that caused the event to occur, then you may be able to just do

 function BytesAvailable_Callback(obj,event)

 myData = fgets(obj);

I haven't tested this out, but it may be worth trying because it would simplify the code (and avoid troublesome global variables).