Instrument Control Toolbox | ![]() ![]() |
Write text to the instrument, and read data from the instrument
Syntax
out = query(obj,'cmd') out = query(obj,'cmd','wformat
') out = query(obj,'cmd','wformat
','rformat
') [out,count] = query(...) [out,count,msg] = query(...)
Arguments
Description
out = query(obj,'cmd')
writes the string cmd
to the instrument connected to obj
. The data read from the instrument is returned to out
. By default, the %s\n
format is used for cmd
, and the %c
format is used for the returned data.
out = query(obj,'cmd','
writes the string wformat
')
cmd
using the format specified by wformat
.
wformat
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 sprintf
file I/O format specifications or a C manual for more information.
out = query(obj,'cmd','
writes the string wformat
','rformat
')
cmd
using the format specified by wformat
. The data read from the instrument is returned to out
using the format specified by rformat
.
rformat
is a C language conversion specification. The supported conversion specifications are identical to those supported by wformat
.
[A,count] = query(...)
returns the number of values read to count
.
[A,count,msg] = query(...)
returns a warning message to msg
if the read operation did not complete successfully.
Remarks
Before you can write or read data, obj
must be connected to the instrument with the fopen
function. A connected instrument object has a Status
property value of open
. An error is returned if you attempt to perform a query operation while obj
is not connected to the instrument.
query
operates only in synchronous mode, and blocks the command line until the write and read operations complete execution.
Using query
is equivalent to using the fprintf
and fgets
functions. The rules for completing a write operation are described in the fprintf
reference pages. The rules for completing a read operation are described in the fgets
reference pages.
Example
This example creates the GPIB object g
, connects g
to a Tektronix TDS 210 oscilloscope, writes and reads text data using query
, and then disconnects g
from the instrument.
g = gpib('ni',0,1); fopen(g) idn = query(g,'*IDN?') idn = TEKTRONIX,TDS 210,0,CF:91.1CT FV:v1.16 TDS2CM:CMV:v1.04 fclose(g)
Functions
fopen
, fprintf
, fgets
, sprintf
Properties
![]() | propinfo | readasync | ![]() |