External Interfaces Reference |
Read data from the device, and format as text
Syntax
A = fscanf(obj) A = fscanf(obj,'format
') A = fscanf(obj,'format
',size) [A,count] = fscanf(...) [A,count,msg] = fscanf(...)
Arguments
Description
A = fscanf(obj)
reads data from the device connected to obj
, and returns it to A
. The data is converted to text using the %c
format.
A = fscanf(obj,'
reads data and converts it according to format
')
format
. format
is a C language conversion specification. Conversion specifications involve the %
character and the conversion characters d, i, o, u, x, X, f, e, E, g, G, c, and s. Refer to the sscanf
file I/O format specifications or a C manual for more information.
A = fscanf(obj,'
reads the number of values specified by format
',size
)
size
. Valid options for size
are:
n |
Read at most n values into a column vector. |
[m,n] |
Read at most m-by-n values filling an m-by-n matrix in column order. |
size
cannot be inf
, and an error is returned if the specified number of values cannot be stored in the input buffer. If size
is not of the form [m,n]
, and a character conversion is specified, then A
is returned as a row vector. You specify the size, in bytes, of the input buffer with the InputBufferSize
property. An ASCII value is one byte.
[A,count] = fscanf(...)
returns the number of values read to count
.
[A,count,msg] = fscanf(...)
returns a warning message to msg
if the read operation did not complete successfully.
Remarks
Before you can read data from the device, it must be connected to obj
with the fopen
function. A connected serial port object has a Status
property value of open
. An error is returned if you attempt to perform a read operation while obj
is not connected to the device.
If msg
is not included as an output argument and the read operation was not successful, then a warning message is returned to the command line.
The ValuesReceived
property value is increased by the number of values read - including the terminator - each time fscanf
is issued.
If you use the help
command to display help for fscanf
, then you need to supply the pathname shown below.
Rules for Completing a Read Operation with fscanf
A read operation with fscanf
blocks access to the MATLAB command line until:
Terminator
property is read.
Timeout
property passes.
size
is read.
size
is specified)
Example
Create the serial port object s
and connect s
to a Tektronix TDS 210 oscilloscope, which is displaying sine wave.
Use the fprintf
function to configure the scope to measure the peak-to-peak voltage of the sine wave, return the measurement type, and return the peak-to-peak voltage.
fprintf(s,'MEASUREMENT:IMMED:TYPE PK2PK') fprintf(s,'MEASUREMENT:IMMED:TYPE?') fprintf(s,'MEASUREMENT:IMMED:VALUE?')
Because the default value for the ReadAsyncMode
property is continuous
, data associated with the two query commands is automatically returned to the input buffer.
Use fscanf
to read the measurement type. The operation will complete when the first terminator is read.
Use fscanf
to read the peak-to-peak voltage as a floating-point number, and exclude the terminator.
Disconnect s
from the scope, and remove s
from memory and the workspace.
Functions
fgetl
, fgets
, fopen
, fread
, strread
Properties
BytesAvailable
, BytesAvailableFcn
, InputBufferSize
, Status
, Terminator
, Timeout
fread (serial) | fwrite (serial) |
© 1994-2005 The MathWorks, Inc.