[time-nuts] A Prologix GPIB-USB hint
Poul-Henning Kamp
phk at phk.freebsd.dk
Sat Jun 9 14:32:06 UTC 2007
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
phk at FreeBSD.ORG | 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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