User`s manual

Writing and Reading Data
8-29
Writing and Reading Data
For many serial port applications, there are three important questions that you
should consider when writing or reading data:
•Will the read or write function block access to the MATLAB command line?
•Is the data to be transferred binary (numerical) or text?
•Under what conditions will the read or write operation complete?
For write operations, these questions are answered in “Writing Data” on page
8-31. For read operations, these questions are answered in “Reading Data” on
page 8-36.
Example: Introduction to Writing and Reading Data
Suppose you want to return identification information for a Tektronix TDS 210
two-channel oscilloscope connected to the serial port COM1. This requires
writing the
*IDN? command to the instrument using the fprintf function, and
then reading back the result of that command using the
fscanf function.
s = serial('COM1');
fopen(s)
fprintf(s,'*IDN?')
out = fscanf(s)
The resulting identification information is shown below.
out =
TEKTRONIX,TDS 210,0,CF:91.1CT FV:v1.16 TDS2CM:CMV:v1.04
End the serial port session.
fclose(s)
delete(s)
clear s
Controlling Access to the MATLAB Command Line
You control access to the MATLAB command line by specifying whether a read
or write operation is synchronous or asynchronous.
A synchronous operation blocks access to the command line until the read or
write function completes execution. An asynchronous operation does not block