problem of using serial port

Hello everyone,

I get a trouble with the Instrument control Toolbox.The USB Driver has alreadly installed.

my code:

s1 = serial('COM3');

serialinfo = instrhwinfo('serial') ;

cur = instrfind;

set(s1,'BaudRate',9600) ;

set(s1,'Terminator','CR') ;

fopen(s1) ;

fprintf(s1,'*IDN?') ;

a = fread( s1,10, 'uchar') ;

fclose(s1) ;

delete(s1) ;

clear s1 ;

Warning: Unsuccessful read: The specified amount of data was not returned within
the Timeout period. 

a =

     Empty matrix: 1-by-0

But when the NDI software was closed,the code can connect only one time to the NDI and get a little data with it's length is 10. When I try again, I will get a warn above.

what can I do?

[Walter Roberson]

One thing to keep in mind is that fread() is to read an exact number of bytes (or all bytes until end of file), and is not intended to read "a line" which is what you are probably looking for.

I don't think this will fix your difficulty in this situation, but switching to fgetl() would help once you get past the timeout problem.

[Walter Roberson]

Fan Sudi wrote,

I have tried,but get a empty matrix. Warning: Unexpected Warning: A timeout occurred before the Terminator was reached. a = '' but the first loop get a string "RESETBE6F",the others empty.