Agilent Technologies E2094S Uživatelská příručka stáhnout pdf (Strana 129)

Programming via USB 6

Agilent VISA User’s Guide 129

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 29 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

1 2 ... 124 125 126 127 128 129 130 131 132 133 134 ... 145 146

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Agilent Technologies E2094S Uživatelská příručka Strana 129