Hi Steve:
In addition to what John has already said I'm like to remind you that many HP instruments were built using a Motorola 68000 uC and it's clock speed is much slower than today's PCs so it's good to put in some time delays to give the instrument time to process the command.
Have Fun,
Brooke Clarke
w/Java
w/o Java
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1a. GPIB comms with 8753C
Posted by: "sadavis80" Steve@... sadavis80
Date: Thu Jan 25, 2007 6:07 am ((PST))
I have been using a USB-GPIB-A adapter to talk to my 8753C and
continue to have trouble sending and reading information without
errors. Has anyone else used GPIB to communicate with an 8753?
I have finally found what should be sufficient documentation, but it
just doesn't want to work the way the book says. The OPC commands
"seem" to work the way they should - I get the '1' response, however,
often times the following command will generate an error and will not
be recognized. On reads using a command like
POIN 201; CHAN1; FORM4; SING; OUTPFORM;
(copied from an example program from HP)
I almost always get the first point response, but the rest often do
not come and I get a timeout error. If I put the entire sequence in a
loop (loops back on timeout error), then it will read correctly some
times and some times it will fail. I have tried MANY MANY different
delays between the sequential reads and have finally gotten it to work
fairly reliably, but acquiring the data takes considerably longer than
it should (due to the required delays).
Yesterday, I thought I realized that the 'CHAN1;' part of the above
was causing problems so I separated the command and now send
POIN 201; CHAN1; FORM4;
as a separate command before the point loop (CHAN1 is OPC'able, but it
doesn't seem to matter). Then a short delay and then
SING; OUTPFORM;
before entering the read data loop. It seems to work a little more
reliably, but I still have to have more delay than should be necessary
between read requests (ibrd). I also determined that if I read the
first 10 points or so slower and "get it going" (so to speak), I can
then drop the delays altogether and read the subsequent points without
error (MOST of the time).
This all just seems WEIRD to me - I wonder if my 8753 has a problem or
is it just characteristic of that model. I'm using a fairly fast
computer (1.5 - 2 GHZ Intel PC with WinXP), but the docs say the GPIB
drivers should 'get' the data when the 8753 is ready to send it - but
it doesn't work that way exactly. Apparently, I can make the ibrd
request before the 8753 can recognize it and it hoses the works. I
wonder if the older GPIB drivers and the older 8753 just weren't
designed to work with these new much faster computers?
Anyone have info, thoughts or ideas?
tia,
Steve
