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Re: data acquisition, device control [message #3484 is a reply to message #3406]

Mon, 30 January 1995 09:01

Gary Kushner
Messages: 5
Registered: December 1994

Junior Member

Richard Olsen <olsen@physics.nps.navy.mil> wrote:
>
> We'd like to use IDL as a front-end for data acquisition on a PC,
> which basically means being able to talk to an A-D converter, and
> presenting the results in ~real time with IDL
>
> Has anyone done this, or something similar?
>
> rc olsen
> olsen@physics.nps.navy.mil

We have also been using IDL to control several devices in our lab.
We use the CALL_External function and have also used
the OUTPW and INPW(?) calls. The OUTPW and INPW calls allow
you to write and read ports and boards on a PC. You need to
know the base addresses of the boards you want to communicate to.

We use CALL_EXTERNAL to control our GPIB devices and to collect
data from a microchannel plate detector system. Our data acquisition
system consists of a National Instruments GPIB card and a National
Instruments digital I/O card. We wrote a windows dll that acts as
a "wrapper" for the GPIB functions provided by National Instruments.
For the digital I/O we required a fast data acquisition rate. We
wrote a windows dll to directly control the I/O card and to
collect the data. The dll then passes the data to IDL.

Dll's are not that difficult to write. Getting CALL_EXTERNAL
to talk to your dll can be a little tricky though.

The main problem we encountered was that a windows 3.1x dll can
only pass 64k of data at a time. Thus, if you wish to acquire
a large amount of data, you have to write your IDL code and your dll
to pass the data in small chunks or you could use interrupt
driven code. I am thinking of switching to Windows NT so that I can
have the process run under a different thread and so I can ignore
the 64k limit.

If anyone is interested, I can make available our IDL code and our
dll source code.

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[Message index]

		data acquisition, device control By: Richard Olsen on Thu, 26 January 1995 11:01
		Re: data acquisition, device control By: Gary Kushner on Mon, 30 January 1995 09:01
		Re: data acquisition, device control By: rivers on Sat, 28 January 1995 13:28
		Re: data acquisition, device control By: kaaret on Thu, 02 February 1995 10:18

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