Write text to instrument, and read data from instrument
out = query(obj,'cmd')
out = query(obj,'cmd','wformat')
out = query(obj,'cmd','wformat','rformat')
[out,count] = query(...)
[out,count,msg] = query(...)
[out,count,msg,datagramaddress,datagramport] = query(...)
An interface object.
String that is written to the instrument.
Format for written data.
Format for read data.
Contains data read from the instrument.
The number of values read.
A message indicating if the read operation was unsuccessful.
The datagram address.
The datagram port.
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.
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.
rformat is a C language conversion specification. The supported conversion specifications are identical to those supported by wformat.
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)
Before you can write or read data, obj must be connected to the instrument with the fopen function. A connected interface 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.