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GPIB-USB Controller 6.0 FAQ

  1. How do I verify communication with an instrument (using Prologix GPIB Configurator utility)?

    1. Disconnect GPIB-USB Controller from instrument and from PC.
    2. Download and install Prologix GPIB Configurator utility.
    3. Connect GPIB-USB Controller to PC.
    4. Run Prologix configurator and select USB Serial Port.
    5. Set configuration to CONTROLLER.
    6. Enable (check) auto-read-after-write.
    7. Enable (check) assert EOI with last transmitted byte.
    8. Set GPIB address to X, where X is the GPIB address of the instrument.
    9. Type ++ver in the command box and click the Send button. GPIB-USB Controller version is displayed in the Terminal box.
    10. Connect GPIB-USB to instrument.
    11. Type a valid instrument command in the command window and click the Send button. The response, if any, from the instrument is displayed in the Terminal box.
  2. How do I verify communication with an instrument (using a terminal program)?

    1. Disconnect GPIB-USB Controller from instrument and from PC.
    2. Connect GPIB-USB Controller to PC.
    3. Using a terminal program, connect to USB Serial Port. Port settings, such as baud rate, do not matter.
    4. Enter ++mode 1. See Manual for command details.
    5. Enter ++auto 1. See Manual for command details.
    6. Enter ++addr X, where X is the GPIB address of the instrument. See Manual for command details.
    7. Enter ++ver. GPIB-USB Controller version is displayed.
    8. Connect GPIB-USB to instrument.
    9. Enter a valid instrument command. The response, if any, from the instrument is displayed.
  3. How does Prologix GPIB-USB controller compare to products from other vendors?

    While Prologix GPIB-USB controller provides many of the same features as GPIB-USB controllers from other vendors, it is much easier to use. Prologix GPIB-USB controller provides a virtual serial interface to communicate with instruments, while handling all GPIB protocol details for you. As a result, you can communicate easily with instruments using any terminal program instead of having to write custom programs using vendor supplied library. Please see the Manual for a complete list of features.
  4. Is Prologix GPIB-USB controller compatible with National Instruments LabVIEW, Agilent VEE, and other test frameworks?

    Yes. Prologix GPIB-USB controller provides a virtual serial interface to communicate with instruments, while handling all GPIB protocol details for you. Any test framework, or programming environment, that provides access to serial ports is compatible with Prologix GPIB-USB controller. For example, you may use NI LabVIEW Serial VIs or NI VISA VIs. Also, see LabVIEW samples on communicating with the controller using D2XX drivers.
  5. How do I use Prologix GPIB-USB controller with LabVIEW?

    Prologix GPIB-USB controller provides a virtual serial interface to communicate with instruments. Therefore you may use LabVIEW serial port functions or VISA serial port functions to talk to Prologix controller and attached instruments. Please see LabVIEW sample program in the Resources section.

    The basic steps to communicate with an instrument in LabVIEW are as follows:

    1. Open USB Serial Port. Port settings, such as baud rate, do not matter.
    2. Send ++mode 1 terminated with Line Feed. See Manual for command details.
    3. Send ++auto 1 terminated with Line Feed. See Manual for command details.
    4. Send ++addr X terminated with Line Feed, where X is the GPIB address of the instrument. See Manual for command details.
    5. Send a valid instrument command terminated by Line Feed.
    6. Read USB Serial Port for instrument response.

    Linux users: See Matthias Schroeter's web page on how to use Prologix GPIB-USB Controller with LabVIEW on Linux,

  6. How do I use Prologix GPIB-USB controller with MATLAB, or using C++, C#, or Visual Basic?

    Please see sample programs in the Resources section.
  7. Will my LabVIEW or VEE programs work unmodified with Prologix GPIB-USB controller?

    Probably not. Prologix GPIB-USB controller provides a virtual serial interface to communicate with instruments, while handling all GPIB protocol details for you. Programs that expect a different interface (such as NI 488.2 interface) have to be modified to use the serial interface to be compatible with Prologix GPIB-USB controller.
  8. Is Prologix GPIB-USB controller a drop-in replacement for controllers from other vendors?

    No. Prologix GPIB-USB controller provides a virtual serial interface to communicate with instruments, while handling all GPIB protocol details for you. Programs that expect a different interface (such as NI 488.2 interface) have to be modified to use the serial interface to be compatible with Prologix GPIB-USB controller.
  9. What accessories are needed to use Prologix GPIB-USB controller?

    At a minimum, you need an USB A-B cable, with an USB-A connector at one end, and an USB-B connector at the other end. You may also need a GPIB cable.

    A power supply is not needed since Prologix GPIB-USB controller is powered from the USB bus. You may plug the Prologix GPIB-USB controller directly onto the GPIB connector on the instrument. The controller has a male GPIB connector and most instruments have a female GPIB connector. However, if it is not convenient to do so, you may use a GPIB cable.

  10. How do I install drivers?

    Please refer to FTDI installation guides.
  11. How do I configure my Prologix GPIB-USB controller?

    There are two easy ways to configure your Prologix GPIB-USB controller:
    • Use the excellent open source Prologix GPIB Configurator utility written by John Miles.
    • Use a terminal program such as HyperTerminal or Tera Term Pro and enter commands manually as described in the User Manual.
  12. How do I download and print screen plots from instruments?

    To download and print plots you need a plotter emulation application such as:
    • 7470.exe — an excellent open source application.
    • PrintCapture — a full-featured commercial application. 30-day free trial version available.
    • Plottergeist — another full-featured commercial application.
  13. How do I use 7470 (HP 7470A plotter emulator) application with Prologix GPIB-USB controller?

    Here are quick start steps for using 7470 application:
    1. Connect GPIB-USB to PC.
    2. Run Prologix GPIB Configurator (which is part of 7470 download) and select USB serial port corresponding to GPIB-USB.
    3. Set configuration to DEVICE, GPIB address to 5, and click "Update CONNECT.INI" button. See picture.
    4. Close Prologix GPIB Configurator.
    5. Connect GPIB-USB to instrument, directly, or using a GPIB cable.
    6. Run 7470 application and press 'w' to wait for plot data from instrument.
    7. Start plot from instrument front panel.
    Please see 7470 User Guide for more details.
  14. How do I use PrintCapture with Prologix GPIB-USB controller?

    Please see application note in the Resources section. Also see PrintCapture website for more details.
  15. How do I use Plottergeist with Prologix GPIB-USB controller?

    1. Connect GPIB-USB to PC.
    2. Configure GPIB-USB as DEVICE and set GPIB address to 5.
    3. Connect GPIB-USB to instrument, directly, or using a GPIB cable
    4. Start Plottergeist.
    5. Open Configuration | GPIB/RS-232... dialog. Select Connect using Serial Port, and click Setup. Select USB serial port corresponding to GPIB-USB.
    6. Click OK twice. Click the On Line button on the tool bar.
    7. Start plot from instrument front panel.
  16. How do I use HyperTerminal with Prologix GPIB-USB controller?

    1. Connect GPIB-USB to PC.
    2. Start HyperTerminal. (HyperTerminal application can usually be found in Start | Programs | Accessories | Communications menu.)
    3. Open File | Properties dialog.
    4. In the Connect To tab, select USB serial port corresponding to GPIB-USB.
    5. In the Settings tab, click ASCII setup.... In the new dialog, check Send line ends with line feeds and Echo typed characters locally.
    6. Click OK twice.

    You are now ready to communicate with the controller. Enter ++ver command in the HyperTerminal window to verify communication with controller.

  17. How do I use Tera Term Pro with Prologix GPIB-USB controller?

    1. Connect GPIB-USB to PC.
    2. Start Tera Term Pro.
    3. Open Setup | Serial Port... dialog. Select USB serial port corresponding to GPIB-USB. Click OK.
    4. Open Setup | Terminal dialog. Set Transmit to CR+LF, and check Local echo. Click OK.

    You are now ready to communicate with the controller. Enter ++ver command in the Tera Term Pro window to verify communication with the controller.

  18. Which commands do I use to control my instrument?

    Refer to the programming manual of your instrument for commands accepted by your instrument.
  19. How do I create programs to control instruments, and acquire data, using Prologix GPIB-USB controller?

    Any programming language and environment that provides access to serial ports may be used to develop programs to control instruments using the Prologix GPIB-USB controller. Please see sample programs in the Resources section. Also, check out Ulrich Bangert's EZGPIB, an easy to use data acquisition tool for use with Prologix GPIB-USB controller.
  20. Can Prologix GPIB-USB controller control multiple instruments?

    Yes. Specify the GPIB address of the instrument to control using the ++addr command. All subsequent instrument commands are sent to the specified address. When you want to control a different instrument, issue another ++addr command with the new address. See User Manual for complete details and samples.
  21. Why is the instrument not responding to commands?

    Some common reasons are:
    • Wrong serial port is being used.
    • Prologix GPIB-USB controller is not in CONTROLLER mode.
    • Prologix GPIB-USB controller does not have the correct instrument GPIB address.
    • Read-after-write may not be enabled. See User Manual.
    • Instrument is not in TALK/LISTEN mode. Check instrument front panel menu, or back side DIP switch.
    • Prologix GPIB-USB controller is not securely connected to instrument. Try using a GPIB cable, if direct connection is not secure.
    • Other instruments on the GPIB bus may be interfering. Disconnect (not just power down) all instruments except the one being used.
    • Command is not recognized by the instrument. Check instrument programming manual.
  22. Why is the instrument reporting QUERY UNTERMINATED or ERROR -420 error when using Prologix GPIB-USB controller?

    After sending a command to an attached instrument, Prologix GPIB-USB controller will address it to talk to read back the response. If the command does not generate a response (often called non-query commands), some instruments will generate the QUERY UNTERMINATED error when addressed to talk. In effect the instrument is saying, you have asked me to talk but I have nothing to say. The error is often benign and may be ignored.

    However, if you wish to avoid the error use the ++read command to read instrument responses. For example:
    ++auto 0Turn off read-after-write
    SET VOLT 1.0Non-query command
    *idn?Query command
    ++read eoiRead until EOI is asserted by instrument
    "HP54201A"Response from instrument
    See User Manual for complete details.