Phatom GPIB device #21

[Torsten Bronger]

Halloechen!

I try to find all conncected GPIB devices with the GPIB function
"FindLstn".  However, additionally to the really connceted devices
this function find something with address #21.  If I disconnect all
devices, it really finds nothing (as expected).  But no matter
which devices are activated (Keithley, an ols Epson printer and a
homebrew thing), this #21 appears on the list.

I use a GPIB-USB-B.

I call the routine in a C++ program as follows:

    FindLstn(GPIB0, Instruments, Result, 31);
    if (ibsta & ERR)
    {
       GPIBCleanup(GPIB0, "Unable to issue FindLstn call");
       return 1;
    }

    int Num_Listeners = ibcntl;

    for (int i=0; i < Num_Listeners; i++)
        cout << Result[i] << '\n';


This odd phantom device seems to become a problem when "SendList"
ist called:

    SendList(GPIB0, Result, "*IDN?", 5L, NLend);

This call always fails.

Any ideas what's happening here?  Thank you!

Tschoe,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus