Alternative GPIB Interfaces

In most situations, GPIB communication is between a physical GPIB board and a GPIB instrument. But what if you have a serial instrument that you would like to control on your GPIB bus? Or what if your computer does not have room for a GPIB board? You still can use GPIB communication. You will need either a GPIB controller or a GPIB converter.

Several types of GPIB controllers are available: Ethernet, parallel port, IEEE 1394, USB, 232 (serial), and 485 (serial). A controller connects the GPIB instrument to your computer instead of using a GPIB board for the connection. For example, the serial controller makes a connection from your serial port to your GPIB instrument. The controller gives you the capability to use NI-488 or NI-488.2M commands to talk to your GPIB instrument. As a result, you could talk to your serial instrument using GPIB commands. The GPIB controllers give you the functionality of a GPIB board. As with a board, the controllers usually can support 14 instruments.

A converter is different than a controller. A converter simply translates the data between two ports. For example, a serial converter translates serial commands to GPIB commands. To talk to your instrument using a converter attached to the serial port, you use serial communication to talk to the converter. The converter then translates the serial commands to GPIB to send to the instrument. You also can use the converter in conjunction with a GPIB board and a serial instrument. In this case, the converter translates the GPIB commands to serial commands for the instrument. The converters can translate data for only one instrument.

Using alternative GPIB devices has many advantages. If you do not have an empty slot in your computer for your GPIB board, the controllers provide GPIB functionality through another outlet, such as serial or parallel. Alternative devices also give you the ability to use GPIB programming, rather than serial commands, with a serial instrument. In addition, depending on the controller used, you can extend GPIB communication. For example, the RS-485 controller can extend GPIB up to 1.2 km (4000 ft).

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