User`s guide

Programming via USB 6
Agilent VISA User’s Guide 143
Communicating with a USB Instrument Using VISA
To establish communications with a USB device using VISA,
you can either use the full VISA resource string for the
device or use the alias provided by VISA. Using the alias is
recommended, for reasons described below.
Using the full VISA resource string, a viOpen call would look
something like this:
viOpen( . . .,
"USB0::2391::1031::0000000123::0::INSTR", . . .
);
Following is a summary of the components of this call.
This string uniquely identifies the USB device. The values
needed for the resource string are displayed in a dialog box
when the device is plugged into the computer.
To simplify the way a USB device is identified, Agilent VISA
also provides an alias which can be used in place of this
resource string. The first USB device that is plugged in is
assigned a default alias of UsbDevice1. Additional devices are
assigned aliases of UsbDevice2, UsbDevice3, etc. You can
modify the default alias name at the time a device is plugged
in, or by running Agilent Connection Expert and changing
the properties of the VISA alias.
Table 34 Summary of Full-String viOpen Call
Value Description Data Type
2391 Manufacturer ID 16-bit unsigned integer
1031 Model Code 16-bit unsigned integer
0000000123 Serial Number string value
0 USBTMC Interface Number 8-bit unsigned integer