Question:

33120A: How do I troubleshoot the RS-232 connection for Benchlink Arb?

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 Arb.

    It is always a good idea to start your troubleshooting process by checking your version of Benchlink Arb and upgrading it if necessary. In Benchlink Arb, click Help | About... . As of Jan 1, 2000 the latest revision is version 1.3. Free upgrades are available at: ftp://hpcsos.col.hp.com/dist/Benchlink/arbup.exe .

    2. Make sure your 33120A''s RS-232 settings match Benchlink''s settings.

    Start Benchlink Arb. In the "Search for an instrument" dialog box click "Cancel".

    a. Click Options | Configure Interface. 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 a Parity of None. f. Choose 8 Data Bits. g. Choose 1 Stop Bit. h. Choose "Xon/Xoff" for Flow Control. i. The "ID Query" field should read "*idn?". j. Leave the "Serial Port Settings" dialog box open for now.

    On the 33120A:

    a. Enter the Menu system by pressing "Shift-Enter". b. Use the right arrow key to move to the "I/O MENU". c. Use the down arrow key to enter the I/O Menu. d. Use the right arrow key to move to "INTERFACE". e. Use the down arrow to view the Interface setting. If the display shows "RS-232" then use the up arrow key to return to "INTERFACE". Otherwise use the right arrow and then "Enter" to change it now. You will then need to recall your menu position by hitting "Shift-Recall Menu". f. Use the right arrow key to move to "BAUD RATE". g. Use the down arrow key to view the Baud Rate setting. If the display shows "9600 BAUD" then use the up arrow key to return to "BAUD RATE". Otherwise use the right arrow and then "Enter" to change it now. You will then need to recall your menu position by hitting "Shift-Recall Menu". h. Use the right arrow key to move to "PARITY". i. Use the down arrow key to view the Parity setting. If the setting is "NONE: 8 BITS" then hit "Enter" to exit the menu system. Otherwise use the right arrow and then "Enter" to change it now.

    Now go back to Benchlink Arb and try to find the instrument.

    a. In the "Serial Port Settings" dialog box, click "Test". b. If "Found a 33120A..." 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 33120A is listed in the "Instrument" column, then you are now successfully connected and you may click "OK" to start using Benchlink Arb. e. If the 33120A is not listed, click "Search". f. If Benchlink Arb found the instrument, you are done. If it is still not listed go on to step 3.

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

    If you "Test" your settings in Benchlink Arb''s "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 configuration.

    a. Shut down Benchlink Arb. 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 Arb. 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 in Benchlink Arb, 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".

  3. Verify proper RS-232 cable type.

    A null-modem serial cable is required for use with the 33120A. The 33120A 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 cables and other commercially available cables sometimes work, the 34398A cable has proven reliable with the 33120A. 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.

  4. Try other combinations of communication settings.

    Occasionally RS-232 settings will not work even though the instrument''s settings match Benchlink Arb''s. If this happens, experiment with different settings for Flow Control and Stop Bits. Note that this can be done within Benchlink Arb, without making changes to the 33120A.

  5. 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.

  6. Verify that your unit does not have a known RS-232 problem.

    If your unit''s serial number lies between either of the following ranges, it may be subject to the indicated problem.

    US00000000/US34017350 RS-232 transmits invalid characters US36015500/US36017189 Bad IC prevents RS-232 communication

    Please contact your local Agilent Test & Measurement Call Center for information on repairing or replacing the unit.

  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 33120A with?

    These steps might help pin down where further troubleshooting efforts should be directed.

    Revision 1.0 20 DEC 99 jtm