Low cost GPIB-USB controller

[[email protected]]

Hello all,

A low cost GPIB-USB controller is now available from:
http://www.sparkfun.com/commerce/product_info.php?products_id=549

It can be used to control GPIB instruments and download data and screen
plots.

Thanks,

 

[Joerg]

Hello all,

A low cost GPIB-USB controller is now available from:
http://www.sparkfun.com/commerce/product_info.php?products_id=549

Nice, but $125 isn't exactly low cost. It's a long time ago but we used
to buy GPIB card for the old ISA bus for under $100. Think about another
"de-featured" version. Most people only need them to get screen prints
out of an instrument, not to control them.

Regards, Joerg

 

[[email protected]]

Joerg,

Thanks for your suggestion.
Compared to the $500 GPIB-USB dongles from NI, Agilent and others isn't
$125 low cost?

Regards,

 

[Joel Kolstad]

Compared to the $500 GPIB-USB dongles from NI, Agilent and others isn't
$125 low cost?

Sure, for the hardware... but is your converter compatible (software-wise)
with the NI cards? Are there LabView drivers for it? If the answer to either
of those is "no," I can tell you that a lot of companies won't care about your
low price -- the engineering time to modify their software wouldn't make it
worthwhile. (True story -- that I've mentioned before --: Tektronix still
uses PDP-11's as part of their probe manufacturing lines. Although they pay
an arm and a leg to keep those PDPs alive, it's apparently cheaper than
migrating to newer, cheaper hardware and porting the software!)

I was rather pleased to find that some old test software we had for an NI ISA
GPIB card worked flawlessly (no changes required) with the NI USB GPIB
dongles; they've maintained pretty broad compatibility between all their
interfaces over time (granted, they aren't perfect -- their _original_
USB<-->GPIB dongle was only supported up through Windows 98... grrr!).
Similarly, NI provides some nice LabView drivers (no surprise there, eh?) that
make it very fast to development LabView apps that "speak" GPIB.

For someone writing new software, though, I think your dongle looks like a
good bargin. Although you might want to stick it in a case to make it look
more like a "finished product!"

---Joel Kolstad

 

[Joerg]

Hello Joel,

For USB it is, but there are (were?) ISA cards for much less.

Sure, for the hardware... but is your converter compatible (software-wise)
with the NI cards? Are there LabView drivers for it? If the answer to either
of those is "no," I can tell you that a lot of companies won't care about your
low price -- the engineering time to modify their software wouldn't make it
worthwhile. ...

Not that it was required but the cheap ISA cards actually were fairly
compatible, AFAIR. I have to say though that their documentation was
hardly intelligible but for us it worked.

... (True story -- that I've mentioned before --: Tektronix still
uses PDP-11's as part of their probe manufacturing lines. Although they pay
an arm and a leg to keep those PDPs alive, it's apparently cheaper than
migrating to newer, cheaper hardware and porting the software!)

Oh man. Time to make the switch before something breaks and cannot be
replaced. This is like flying a critical mission with a DC3. Not that it
wouldn't be safe but one busted engine can put you out of service for a
long time. Sometimes a down-time of a few weeks can bring great troubles.

I have modernized quite some production gear, usually after asking
questions like "What if this thing over here breaks?" and the response
was an eerie silence.

Regards, Joerg

 

[[email protected]]

Sure, for the hardware... but is your converter compatible (software-wise)
with the NI cards? Are there LabView drivers for it?

On the other hand, if his dongle crashes less frequently than the NI
one and isnt' too hard to code for, I might see if I can get work to
buy a few of them.

 

[Joel Kolstad]

Hi Joerg,

Oh man. Time to make the switch before something breaks and cannot be
replaced.

I asked them about it (this was a year and a half ago now) and they said
there's some company (or maybe companies) that makes replacement PDP-11 boards
specifically so that companies can keep on using their existing
infrastructure. Bizarre kind of a niche industry to find yourself in...

This was (as you'd expect) on the assembly line for their older probes; not
any of those fancy 6GHz monsters one might choose to purchase instead of a new
car for John.

I have modernized quite some production gear, usually after asking questions
like "What if this thing over here breaks?" and the response was an eerie
silence.

In some companies I've seen the dynamic where management doesn't take internal
suggestions to modernize nearly as seriously as those from an outsider!

---Joel

 

[[email protected]]

I asked them about it (this was a year and a half ago now) and they said
there's some company (or maybe companies) that makes replacement PDP-11 boards
specifically so that companies can keep on using their existing
infrastructure. Bizarre kind of a niche industry to find yourself in...

I can see it now. A big classic old iron case...

Full of big circuit boards...

....each consisting of a single FPGA surrounded by pair of regulators
and bunch of level translators...

 

[Keyser Soze]

Sure, for the hardware... but is your converter compatible (software-wise)
with the NI cards? Are there LabView drivers for it?

The original posters design seems to be a GPIB to SERIAL interface only.

This is not such a bad thing as you don't need LabView, MathLab, TestPoint
or other big bucks instrument control suites.

This design includes a VI to interface with LabView plus all the schematics
and source code to roll your own:

http://lsd.fe.uni-lj.si/gpib/complete.zip

University of Ljubljana
Faculty of Electrical Engineering
Trzaska cesta 25, 1000 Ljubljana, Slovenia
Laboratory of semiconductor devices

There is a article in EDN too:

http://www.edn.com/article/CA6290453.html?spacedesc=designideas

 

[Dave (from the UK)]

Hello all,

A low cost GPIB-USB controller is now available from:
http://www.sparkfun.com/commerce/product_info.php?products_id=549

It can be used to control GPIB instruments and download data and screen
plots.

Thanks,

No thanks - I think I'd rather pick up a National Instruments PCI card
on eBay, which would be 100% software compatible with NI.

If I really needed USB, and it is hard to see why, then I'd probably
still buy a NI one.

--
Dave K MCSE.

MCSE = Minefield Consultant and Solitaire Expert.

Please note my email address changes periodically to avoid spam.
It is always of the form: month-year@domain. Hitting reply will work
for a couple of months only. Later set it manually.

 

[Joerg]

Hello Joel,

In some companies I've seen the dynamic where management doesn't take internal
suggestions to modernize nearly as seriously as those from an outsider!

On this one I was an employee. Being a brand new hire I thought the job
of convincing the big brass would be a nasty process. Luckily, the CEO
was an EE who grasped tech stuff quickly and the BoD was very open to
ideas. They had to get involved because it was well north of $1M in
investments. Sometimes it's good to be upfront with the economics and
submit a water-tight amortization sheet over at least four years. With
that stuff I never wait until someone asks me for such data. Most
important is a good rapport with the CFO since they are the folks who
have to hold their heads out "on the street", as they say.

Regards, Joerg

 

[[email protected]]

No thanks - I think I'd rather pick up a National Instruments PCI card
on eBay, which would be 100% software compatible with NI.

If I really needed USB, and it is hard to see why, then I'd probably
still buy a NI one.

One word: laptops

Why you might ask, would one want to control a GPIB bus with a laptop?

1) Salesmen need to demo GPIB instruments without dragging along a
desktop computer

2) Support engineers need to be able to check out a GPIB instrument
without dragging along a desktop computer or depending on the
customer's equipment.

3) When GPIB equipment is installed in a rack and it is necessary to
try someting out of the ordinary - use a different computer to see if
the problem is with the rack mount one, or ttemporarily use GPIB to
debug a system where it is not ordinarily in use, it's a lot easier to
carry a laptop over to the system, crawl behind the rack with it,
whaterver, than to do so with a desktop.

 

[Tauno Voipio]

Dave (from the UK) wrote:




One word: laptops

Why you might ask, would one want to control a GPIB bus with a laptop?

1) Salesmen need to demo GPIB instruments without dragging along a
desktop computer

2) Support engineers need to be able to check out a GPIB instrument
without dragging along a desktop computer or depending on the
customer's equipment.

3) When GPIB equipment is installed in a rack and it is necessary to
try someting out of the ordinary - use a different computer to see if
the problem is with the rack mount one, or ttemporarily use GPIB to
debug a system where it is not ordinarily in use, it's a lot easier to
carry a laptop over to the system, crawl behind the rack with it,
whaterver, than to do so with a desktop.

There is an electrical problem: Power.

The GPIB bus is a TTL-level bus with quite low impedance.
There is simply not enough power available from USB to
drive the GPIB according to the specifications.

 

[Joerg]

Hello Tauno,

There is an electrical problem: Power.

The GPIB bus is a TTL-level bus with quite low impedance.
There is simply not enough power available from USB to
drive the GPIB according to the specifications.

Huh? If 2.5 Watts ain't enough then I don't know what you want to drive
with it:
http://www.digi.com/pdf/prd_usb_usbplusseries_appnote.pdf

Ok, it won't power your espresso machine...

Regards, Joerg

 

[[email protected]]

There is an electrical problem: Power.

The GPIB bus is a TTL-level bus with quite low impedance.
There is simply not enough power available from USB to
drive the GPIB according to the specifications.

What do you think the bus impedance is?

I think it's fairly high, but dependent on the number of devices. Each
device should have a 3k resistor to 5v and a 6.2k resistor to ground,
of course in parallel with the actual input gate. Load up a bus to its
maximum device count so you have many of these in parallel and you
might see problems, but typically with a USB dongle you have few
devices - most often only 1 device. I don't see this exceeding the
post-enumeration USB current limit.

I also think it would be perfectly legitimate to make a device which
was specified in bold letters right on it, "only for direct connection
to a single instrument without an intervening cable" This is after all
the most common use of the USB-GPIB dongles on the market.