HINTS & TIPS

Q. How can I troubleshoot RS-232 to GPIB interface related problems for SUN, HP and IBM Work Stations?

A. On most of the supported platforms UTMOST communicates with test equipment through the computer's serial RS-232 port. The interface from this serial port to GPIB is provided by a National Instrument's GPIB convertor box.

There are five areas to check when UTMOST is not able to communicate with the test equipment and these are:

1) The work station's serial port configuration.

2) The UTMOST hardware configuration.

3) The RS232-GPIB cable connections.

4) The GPIB-232CT convertor box dip switch settings.

5) The test equipment address and data communication configuration.

The following sections describe the RS-232 to GPIB configuration for SUN, HP and IBM work stations.

 

SUN-SPARC WORK STATIONS

1) The serial port names in Sun workstations are ttya and ttyb. Newer SUN work station models (Sparc5, 10 and 20) support ttya and ttyb from a single serial port. Unless there is a splitter cable connected to the port, either ttya or ttyb can be accessed from this single port.

2) The UTMOST Device Configuration screen can be accessed by pressing the "Configuration" button in the "Hardware" Menu (Figure 1). The "CPU side" button should be toggled until it reads RS232 TTYA or RS232 TTYB according to the port connection. The correct address of the test equipment should be entered. In this example, a HP4145 is selected and its address is 16. The "Baud rate" button should be toggled until it reads 38400.

3) The RS232 to GPIB convertor box interface cable connection configuration for the SUN work stations is as follows:

 

Figure 1. The UTMOST Device Configuration Screen.

 

   
RS232 computer (25 pin): 2 3 7    
  | | |    
GPIB computer (9 Pin): 2 3 5 4 and  8 are shorted
or          
RS232 computer (25 pin): 2 3 4 5 7
  | | | | |
GPIB computer (25 pin): 3 2 5 4 7

4) The dip switch settings on National Instrument's GPIB-232CT-A convertor box which provide 38400 baud rate are:

Dip Switch Number (From Left to Right): 1 2 3 4 5 6 7 8
Position:  On   On   On   On   On   Off   Off   Off 

5) The HPIB communication settings of the HP4145 should be verified from the front display of the instrument after the equipment is turned on. In the bottom of the display screen the HPIB settings should appear as :

HPIB ( Address#, COMMA, EOI)

The "Address#" should match the number entered in the "Device Configuration"screen. In addition, the data should be "comma" separated and "EOI" should be on. The HPIB configuration can be set using the dip switches which are located on the back panel of the HP4145.

 

HP WORK STATIONS

1) UTMOST, running on HP700 and HP-J200 series workstations, uses the RS232 serial port to communicate with test equipment.

Prior to the release of the HPUX 10.0 operating system, the serial port names in HP workstations were tty00 and tty01. Since the release of HPUX 10.0 these port names have been changed to tty0p0 and tty1p0 respectively. Currently UTMOST supports the port names tty00 and tty01 only. The serial port names can be checked by viewing the contents of the "/dev" directory. If the port names under the "/dev" directory are tty0p0 and tty1p0 a symbolic link to the old names should be established:

Login as root (superuser) and type:

ln -s /dev/tty0p0 /dev/tty00

and

ln -s /dev/tty1p0 /dev/tty01

This should create a symbolic link between the different port names enabling correct UTMOST operations. A more flexible interface procedure in UTMOST is currently under development. This new feature will allow the user to enter the port names and other communication related parameters directly from the "Device Configuration" screen.

2) The UTMOST Device Configuration screen can be accessed by pressing the "Configuration" button in the "Hardware" Menu (Figure 1). The "CPU side" button should be toggled until it reads RS232 TTYA or RS232 TTYB according to the port connection. The correct address of the test equipment should be entered. In this example, HP4145 is selected as the test equipment and its address is 16. This time the "Baud rate" button should be toggled until it reads 9600.

3) The RS232 to GPIB Convertor box interface cable connection for the HP Work Stations is as follows:

RS232 computer (9 pin): 2 3 5    
  | | |    
GPIB computer (9 Pin): 3 2 5 4 and  8 are shorted
or          
RS232 computer (9 pin): 2 3 5    
  | | |    
GPIB computer (25 pin): 2 3 7 5 and  20 are shorted.

4) The dip switch settings on the GPIB-232CT-A convertor box which provide 9600 baud rate are:

Dip Switch Number (From Left to Right): 1 2 3 4 5 6 7 8
Position:  On   Off   On   On   On   Off   Off   Off 

5) The HPIB communication settings of the HP4145 should be verified from the front display of the instrument after the equipment is turned on. In the bottom of the display screen the HPIB settings should appear as :

HPIB ( Address#, COMMA, EOI)

The "Address#" should match the number entered in the "Device Configuration"screen. In addition, the data should be "comma" separated and "EOI" should be on. The HPIB configuration can be set using the dip switches which are located on the back panel of the HP4145.

 

IBM WORK STATIONS

1) The serial port names in IBM Work Stations are tty0 and tty1. UTMOST uses a asynchronous communication and hence the asynchronous terminals should be attached to serial port1 and serial port2. The following command will list the available tty0 or tty1 terminals:

lsdev -C -c tty -H -S a

If the Asynchronous Terminals are not available, the system administration program "smit" should be run to configure the serial ports. After starting "smit" press the "Devices", "TTY", "Add a TTY" buttons respectively. Then select "tty rs232 Asynchronous Terminal" and select serial port1 or serial port2 as the parent adapter.

2) The UTMOST Device Configuration screen can be accessed by pressing the "Configuration" button in the "Hardware" Menu (Figure 1). The "CPU side" button should be toggled until it reads RS232 TTYA or RS232 TTYB according to the port connection. The correct address of the test equipment should be entered. In this example, HP4145 is selected as the test equipment and its address is 16. The "Baud rate" button should be toggled until it reads 9600.

3) The RS232 to GPIB Convertor box interface cable connection for the IBM work stations is as follows:

RS232 computer (25 pin): 2 3 7    
  | | |    
GPIB computer (9 Pin): 3 2 5 4 and  8 are shorted
or          
RS232 computer (25 pin): 2 3 4  5   7 
  | | | | |
GPIB computer (25 pin): 3 2 5  4   7 

4) The dip switch settings on the GPIB-232CT-A convertor box which provide 9600 baud rate are:

Dip Switch Number (From Left to Right): 1 2 3 4 5 6 7 8
Position:  On   Off   On   On   On   Off   Off   Off 

5) The HPIB communication settings of the HP4145 should be verified from the front display of the instrument after the equipment is turned on. In the bottom of the display screen the HPIB settings should appear as :

HPIB ( Address#, COMMA, EOI)

The "Address#" should match the number entered in the "Device Configuration"screen. In addition, the data should be "comma" separated and "EOI" should be on. The HPIB configuration can be set using the dip switches which are located on the back panel of the HP4145.