GPIBNI, VISA, 34401A and *OPC? failing

[Tony Goodhew]

Hi All,

I was trying to run an example program from the manual for a HP 34401A (“Using Status Registers” on page 188) and when it gets to the line:

90 OUTPUT @Dmm; "*OPC?" ! Assure synchronization

The 34401A generates an error -410 “Query Interrupted” if I use the Visa driver. It works fine if I use the GPIBNI driver.

No change in the code, just loading and unloading the device in the Device Setup dialog.

Any thoughts on what I should be looking at?

Thanks,

TonyG

Full App Source:

10 DIM Results$[4096]
20 INTEGER Val,Hpib,Mask,Task
30 ASSIGN @Dmm TO 714
40 CLEAR 7 ! Clear GPIB and dmm
50 OUTPUT @Dmm;"*RST"  ! Reset dmm
60 OUTPUT @Dmm;"*CLS"  ! Clear dmm status registers
70 OUTPUT @Dmm;"*ESE 1"  ! Enable "operation complete" bit to set
80                       ! "standard event" bit in status byte
90 OUTPUT @Dmm;"*SRE 32"  ! Enable "standard event" bit in status byte
100                        ! to pull the IEEE-488 SRQ line
110 OUTPUT @Dmm;"*OPC?"  ! Assure synchronization
120 ENTER @Dmm;Val
130 !
140 ! Configure the multimeter to make measurements
150 !
160 OUTPUT @Dmm;"CONF:VOLT:DC 10"  ! Set dmm to 10 volt dc range
170 OUTPUT @Dmm;"VOLT:DC:NPLC 10"  ! Set the integration time to 10 PLCs
180 OUTPUT @Dmm;"TRIG:COUN 100"  ! Dmm will accept 100 triggers
190 OUTPUT @Dmm;"INIT"  ! Place dmm in "wait-for-trigger" state
210 OUTPUT @Dmm;"*OPC"  ! Set "operation complete" bit in standard event
220                     ! registers when measurement is complete
230 !
240 Hpib=7
250 ON INTR Hpib GOSUB Read_data
260 Mask=2 ! Bit 1 is SRQ
270 ENABLE INTR Hpib;Mask ! Enable SRQ to interrupt the program
280 !
290 ! Execute other tasks while waiting for data
300 !
310 Task=1
320 WHILE Task=1
330 DISP "Taking Readings"
340 WAIT .5
350 DISP ""
360 WAIT .5
370 END WHILE
380 PRINT "Results: ";Results$
390 STOP
400 !
410  Read_data:  !
420 OUTPUT @Dmm;"FETch?"
430 ENTER @Dmm;Results$
440 OUTPUT @Dmm;"*CLS"    ! Clear dmm status registers
450 Task=0
460 RETURN
470 END

[Tony Goodhew]

I reimplemented this in C# using the NI VISA libraries and the code works as expected:

using Ivi.Visa;
using NationalInstruments.Visa;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.ConstrainedExecution;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace SRQTest
{
    internal class Program
    {
        public static GpibSession gpibSession;
        public static NationalInstruments.Visa.ResourceManager resManager;
        public static int gpibIntAddress = 14; // 34401A
        public static string gpibAddress = string.Format("GPIB0::{0}::INSTR", gpibIntAddress);
        public static SemaphoreSlim srqWait = new SemaphoreSlim(0, 1); // use a semaphore to wait for the SRQ events

        static void Main(string[] args)
        {
            // Setup the GPIB connection via the ResourceManager
            resManager = new NationalInstruments.Visa.ResourceManager();

            // Create a GPIB session for the specified address
            gpibSession = (GpibSession)resManager.Open(gpibAddress);
            gpibSession.TimeoutMilliseconds = 8000; // Set the timeout to be 4s
            gpibSession.TerminationCharacterEnabled = true;
            gpibSession.Clear(); // Clear the session

            gpibSession.ServiceRequest += SRQHandler;

            SendCommand("*RST"); // Reset the DMM
            SendCommand("*CLS"); // Clear the DMM status registers
            SendCommand("*ESE 1"); // Enable "operation complete" bit to set "standard event" bit in status byte
            SendCommand("*SRE 32"); // Enable "standard event" bit in status byte to pull the IEEE-488 SRQ line

            var opcResult = QueryString("*OPC?"); // Assure synchronization
            Console.WriteLine($"OPC Result: {opcResult}"); // Print the result of the OPC query

            SendCommand("CONF:VOLT:DC 10"); // Set DMM to 10 volt DC range
            SendCommand("VOLT:DC:NPLC 10"); // Set the integration time to 10 PLCs
            SendCommand("TRIG:COUN 100"); // DMM will accept 100 triggers
            SendCommand("INIT"); // Place DMM in "wait-for-trigger" state
            SendCommand("*OPC"); // Set "operation complete" bit in standard event
            // Wait for the SRQ event
            srqWait.Wait(); // Wait for the SRQ event to be signaled
            // Read the data
            string response = QueryString("FETCH?");
            Console.WriteLine($"1. Response: {response}");
            // Clear the DMM status registers
            SendCommand("*CLS");
        }

        public static void SRQHandler(object sender, Ivi.Visa.VisaEventArgs e)
        {
            // Read the Status Byte
            var gbs = (GpibSession)sender;

            StatusByteFlags sb = gbs.ReadStatusByte();
            Console.WriteLine($"1. SRQHandler - Status Byte: {sb}");

            gpibSession.DiscardEvents(EventType.ServiceRequest);

            SendCommand("*CLS");

            srqWait.Release();
        }

        static private void SendCommand(string command)
        {
            gpibSession.FormattedIO.WriteLine(command);
        }

        static private string ReadResponse()
        {
            return gpibSession.FormattedIO.ReadLine();
        }

        static private string QueryString(string command)
        {
            SendCommand(command);
            return (ReadResponse());
        }
    }
}

Looking at the NI IO Trace Utility, I can see that the HTBasic program differs in that it doesn’t add a 0A to the end of the *OPC? string – Adding END to the OUTPUT statement fixes that and I can continue on but I now run into a problem on line 270 with HT Basic giving an Error 170 “I/O operation not allowed”:

270 ENABLE INTR Hpib;Mask ! Enable SRQ to interrupt the program

If I swap to the GPIBNI driver then the program works successfully.

TonyG

[Mark Thuer]

Tony,

I don’t know what GPIB I/O your using, but the cheap Chinese knockoffs (i.e. for N.I. & Keysight) from eBay have issues. HT Basic uses the device registers to control the GPIB. The knockoffs don’t adhere to the strict register implementation of the original device and rely on the device drivers for data and control transfer.

Hope this helps.

[Tony Goodhew]

I’m using an original NI GPIB-ENET/1000 with the latest NI 488 & VISA drivers.

For clarity, the Basic code works if I use the GPIBNI driver but fails if I use the VISA driver.

That seems to indicate a HT Basic problem and not a problem with the NI Hardware.

[PatB]

Hi Tony,

Thanks for reporting this. I was able to reproduce and will log a ticket to get it fixed.

Thanks,

Pat

[Tony Goodhew]

Thanks Pat – Appreciate it.

TonyG

[Tony Goodhew]

Hey Pat,

Just wondering if this got fixed and if there is any way to get the updated code?

Thanks,

TonyG

[Author]

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