VISA resource names

If you use the method open_resource(), you must tell this function the VISA resource name of the instrument you want to connect to. Generally, it starts with the bus type, followed by a double colon "::", followed by the number within the bus. For example,

GPIB::10

denotes the GPIB instrument with the number 10. If you have two GPIB boards and the instrument is connected to board number 1, you must write

GPIB1::10

As for the bus, things like "GPIB", "USB", "ASRL" (for serial/parallel interface) are possible. So for connecting to an instrument at COM2, the resource name is

ASRL2

(Since only one instrument can be connected with one serial interface, there is no double colon parameter.) However, most VISA systems allow aliases such as "COM2" or "LPT1". You may also add your own aliases.

The resource name is case-insensitive. It doesn’t matter whether you say "ASRL2" or "asrl2". For further information, I have to refer you to a comprehensive VISA description like http://www.ni.com/pdf/manuals/370423a.pdf.

VISA Resource Syntax and Examples

(This is adapted from the VISA manual)

The following table shows the grammar for the address string. Optional string segments are shown in square brackets ([ ]).

Interface

Syntax

ENET-Serial INSTR

ASRL[0]::host address::serial port::INSTR

GPIB INSTR

GPIB[board]::primary address[::secondary address][::INSTR]

GPIB INTFC

GPIB[board]::INTFC

PXI BACKPLANE

PXI[interface]::chassis number::BACKPLANE

PXI INSTR

PXI[bus]::device[::function][::INSTR]

PXI INSTR

PXI[interface]::bus-device[.function][::INSTR]

PXI INSTR

PXI[interface]::CHASSISchassis number::SLOTslot number[::FUNCfunction][::INSTR]

PXI MEMACC

PXI[interface]::MEMACC

Remote NI-VISA

visa://host address[:server port]/remote resource

Serial INSTR

ASRLboard[::INSTR]

TCPIP INSTR

TCPIP[board]::host address[::LAN device name][::INSTR]

TCPIP SOCKET

TCPIP[board]::host address::port::SOCKET

USB INSTR

USB[board]::manufacturer ID::model code::serial number[::USB interface number][::INSTR]

USB RAW

USB[board]::manufacturer ID::model code::serial number[::USB interface number]::RAW

VXI BACKPLANE

VXI[board][::VXI logical address]::BACKPLANE

VXI INSTR

VXI[board]::VXI logical address[::INSTR]

VXI MEMACC

VXI[board]::MEMACC

VXI SERVANT

VXI[board]::SERVANT

Use the GPIB keyword to establish communication with GPIB resources. Use the VXI keyword for VXI resources via embedded, MXIbus, or 1394 controllers. Use the ASRL keyword to establish communication with an asynchronous serial (such as RS-232 or RS-485) device. Use the PXI keyword for PXI and PCI resources. Use the TCPIP keyword for Ethernet communication.

The following table shows the default value for optional string segments.

Optional String Segments

Default Value

board

0

GPIB secondary address

none

LAN device name

inst0

PXI bus

0

PXI function

0

USB interface number

lowest numbered relevant interface

The following table shows examples of address strings:

Address String

Description

ASRL::1.2.3.4::2::INSTR

A serial device attached to port 2 of the ENET Serial controller at address 1.2.3.4.

ASRL1::INSTR

A serial device attached to interface ASRL1.

GPIB::1::0::INSTR

A GPIB device at primary address 1 and secondary address 0 in GPIB interface 0.

GPIB2::INTFC

Interface or raw board resource for GPIB interface 2.

PXI::15::INSTR

PXI device number 15 on bus 0 with implied function 0.

PXI::2::BACKPLANE

Backplane resource for chassis 2 on the default PXI system, which is interface 0.

PXI::CHASSIS1::SLOT3

PXI device in slot number 3 of the PXI chassis configured as chassis 1.

PXI0::2-12.1::INSTR

PXI bus number 2, device 12 with function 1.

PXI0::MEMACC

PXI MEMACC session.

TCPIP::dev.company.com::INSTR

A TCP/IP device using VXI-11 or LXI located at the specified address. This uses the default LAN Device Name of inst0.

TCPIP0::1.2.3.4::999::SOCKET

Raw TCP/IP access to port 999 at the specified IP address.

USB::0x1234::125::A22-5::INSTR

A USB Test & Measurement class device with manufacturer ID 0x1234, model code 125, and serial number A22-5. This uses the device’s first available USBTMC interface. This is usually number 0.

USB::0x5678::0x33::SN999::1::RAW

A raw USB nonclass device with manufacturer ID 0x5678, model code 0x33, and serial number SN999. This uses the device’s interface number 1.

visa://hostname/ASRL1::INSTR

The resource ASRL1::INSTR on the specified remote system.

VXI::1::BACKPLANE

Mainframe resource for chassis 1 on the default VXI system, which is interface 0.

VXI::MEMACC

Board-level register access to the VXI interface.

VXI0::1::INSTR

A VXI device at logical address 1 in VXI interface VXI0.

VXI0::SERVANT

Servant/device-side resource for VXI interface 0.