Question:

34970A: How do I troubleshoot the RS-232 connection for Benchlink Datalogger?

Answer:

RS-232 connections can be difficult to establish at times. There are many potential causes for this difficulty, but usually communication can be established if you follow these steps:

  1. Make sure you have the latest version of Benchlink Datalogger.

    It is always a good idea to start your troubleshooting process by checking your version of Benchlink Datalogger and upgrading it if necessary. In Benchlink, click Help | About... . You will see "Version x.xx". You can check to see if you have the latest version and download a free upgrade patch at the following site: http://www.tm.agilent.com/tmo/datasheets/English/HP_BenchL inkDataLogger.html .

  2. Make sure your 34970A''s RS-232 settings match Benchlink's settings.

    Start Benchlink Datalogger:

    a. Click Instrument | Communication Setup. Alternatively, click "Yes" when prompted to search for an instrument. b. Under "Interfaces", click "Serial RS-232" and then the "Change Settings..." button. c. Select the number of the PC''s COM port that you are using. If you are not sure what it is, you can find it by trial and error. d. Choose a Baud Rate of 9600. e. Choose Parity, Bits: None, 8 bits. f. Choose "Xon/Xoff" for Flow Control. g. Leave the "Serial Port Settings" dialog box open for now. On the 34970A: a. Enter the Interface menu by pressing "Shift", then "Sto/Rcl".
    b. Turn the knob until RS-232 is displayed.
    c. Press "Sto/Rcl", turn the knob until 9600 Baud is displayed.
    d. Press "Sto/Rcl", turn the knob until none, 8 bits is displayed.
    e. Press "Sto/Rcl", turn the knob until Flow XON/XOFF is displayed.
    f. Press "Sto/Rcl" again to save changes and exit the menu.
    Now go back to Benchlink and try to find the instrument.
    a. In the "Serial Port Settings" dialog box, click "Test these settings".
    b. If "Found a 34970A..." appears then you are almost done. If not, move on to step 4.
    c. Click "OK" twice to return to the "Communication Setup" dialog.
    d. If the 34970A is listed in the "Instrument" column, then you are now successfully connected and you may click "OK" to start using Benchlink.
    e. If the 33120A is not listed, click "Search".
    f. If it is still not listed, go on to step 3.

  3. Verify that the blcomm32.ini is configured properly.

    If you "Test" your settings in Benchlink "Communication Setup" and the software finds the instrument, but "Search" does not, this is probably due to a misconfiguration in the Benchlink ini file. Follow the steps below to manually correct the problem.

    a. Shut down Benchlink.
    b. Click Start | Find | Files or Folders...
    c. In the "Named:" field, type "blcomm32.ini".
    d. Ensure that the "Look in:" field is set to search your entire hard drive and click "Find Now".
    e. When the system finds the file (it may show up "blcomm32" or "blcomm32.ini", depending on your system settings), double-click it to open it.
    f. Click "File | Save As..." and in the "Save as type:" field select "All Files". Save the file as "blcomm32.old".
    g. Close the "blcomm32.old" file and back in the "Find: Files" dialog, double-click "blcomm32.ini" again.
    h. Now you will need to look for conflicts between the settings reflected in this .INI file and those you''ve chosen in Benchlink Datalogger. Here is a sample of the first few lines of a blcomm32.ini file:

    [RS232DSA]
    DefaultSettings=9600,NONE,8/1,XON/OFF
    Port=COM1
    [COM1]
    BaudRate=9600
    Parity=NONE
    Length=8
    StopBits=1
    Protocol=XON/XOFF
    IDString1=*idn?

    As a general rule, anywhere you see a setting in these first few lines that conflicts with the settings you''ve chosen, simply make the appropriate change and save the file. For example, if your file looks like the above and you want to use COM2, change the "Port=COM1" line to "Port=COM2". Also change the "[COM1]" line to "[COM2]". If you have difficulties please contact your local Agilent Test & Measurement Call Center. You can, of course, restore the original file at any time by deleting "blcomm32.ini" and renaming "blcomm32.old" to "blcomm32.ini".

  4. Verify proper RS-232 cable type.

    A null-modem serial cable is required for use with the 34970A. The 34970A has a 9-pin male RS-232 port (a DB-9 connector). Your cable must have a DB-9 female connector on one end and a connector to match your computer''s RS-232 port on the other. We highly recommend that you use the Agilent 34398A Cable Kit. While custom-made and other commercially available cables sometimes work, the 34398A cable is proven to be reliable with the 34970A. The 34398A kit includes a DB-9 (female) to DB-9 (female) null-modem cable and one DB-9 (male) to DB-25 (female) adapter. The pinout of the cable is as follows:

    33120A Cable PC
    Pin Pin
    DCD 1---------------1 DCD
    RX 2------\_/------2 RX
    TX 3------/ \------3 TX
    DTR 4------\ /------4 DTR
    GND 5-------X-------5 GND
    DSR 6------/ \------6 DSR
    RTS 7------\_/------7 RTS
    CTS 8------/ \------8 CTS
    RI 9---------------9 RI

    This should be interpreted: Pin 1 to Pin 1, 2 to 3, 3 to 2, 4 to 6, 5 to 5, 6 to 4, 7 to 8, 8 to 7, and 9 to 9.

    The 34398A Cable Kit may be ordered from Agilent Parts Ordering at 877-447-7278.

  5. Try other combinations of communication settings. Occasionally RS-232 settings will not work even though the instrument''s settings match those in Benchlink Datalogger. If this happens, experiment with different settings for Flow Control and Stop Bits. Note that this can be done within Benchlink, without making changes to the 34970A.
  6. Reboot your PC and cycle power on the instrument often.

    Sometimes no communication can be established until one or both the PC and instrument are reset. It is a good idea to reboot both the instrument and the PC on occasion, particularly when you believe you have the correct settings yet you''re still unable to communicate.

  7. Verify that your PC''s RS-232 port works. If you are still unable to communicate at this point, chances are fairly good that there is a problem with your computer''s serial port. Consider the following questions:
    - Has the RS-232 port on this computer been used for successful communication with any instrument or device recently? You may want to consult your IT department or computer manufacturer for assistance in getting the port to work.
    - Do you have access to another RS-232-capable instrument that you could try to communicate with?
    - Do you have access to another computer that you could try to control the 34970A with?
    These steps might help determine where further troubleshooting efforts should be placed.
Revision 1.0 22 DEC 99 MER/jtm