Poul,

This has been fixed in the most recent release. Abdul added a ++read command
that gets a single reading and then turns TALK off the instrument.

I have not actually tried it, but I have received it from Abdul a week or 2
ago.

The firmware isd easy to upgrade.

Give him a call.

Didier 

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Poul-Henning Kamp
Sent: Saturday, June 09, 2007 9:32 AM
To: [email protected]
Cc: [EMAIL PROTECTED]
Subject: [time-nuts] A Prologix GPIB-USB hint


I spent the better part of an afternoon trying to figure this bit out, so to
save somebody else the time:

Some GPIB instruments will complain if addressed to talk when they have not
been asked about anything.  The HP6626A Power Supply is my present instance.

The Prologix GPIB-USB has the "++auto" command which controls if it should
automatically go into listen after a talk, the description on the manual
page is:

        Enable (1) or disable (0) "listen-after-talk" feature

Based on that description, one would, or at least I would, expect the
behaviour to be that nothing happens until the next write, so that this
would work:

        ++auto 0
                                idle bus
        write something
                                device= listen
                                send data
                                idle bus
        ++auto 1
                                idle bus
        write something
                                device= listen
                                send data
                                device= talk
        read something


But that is not the case.  "++auto 1" puts the device in talk mode
immediately, so the sequence needs to be:


        ++auto 0
                                idle bus
        write something
                                device= listen
                                send data
                                idle bus
        write something
                                device= listen
                                send data
                                idle bus
        ++auto 1
                                device= talk
        read something

You've been warned :-)

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED]         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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