"Pickles, Warren" <Warren.Pickles@tycoelectronics.com> wrote:
> I need to send a particular command to an instrument, wait for a precise
> period of time, then send another command. Problem is, this period of time
> needs to be accurate to the microsecond.
That's not going to happen inside any common desktop OS
using any software solution. That includes Linux, Windows, HPUX,
openBSD, whatever. None of these desktop OS's are capable of
realtime control like you are referring to. Consequently no
software of any flavor running inside them will do the job.
If you really need miscrosecond timing you have two basic choices:
(1) use a realtime OS ( there are quite a few ), in which case
you won't be using VEE ( or labview or VB, etc).
or
(2) implement a hardware solution controlled by your application
in a desktop OS. In this case, the realtime control would
be implemented in hardware that is connected to your computer.
The VEE program would read/write data to this controller.
There's many options for buying a realtime controller
or you could build something yourself.
Desktop OS's are great for lots of things- realtime control is not
one of them.
regards
Stan
--------------------------------------------------------------------------
Stan Bischof Agilent Technologies 707-577-3994 stan_bischof@agilent.com
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> I need to send a particular command to an instrument, wait for a precise
> period of time, then send another command. Problem is, this period of time
> needs to be accurate to the microsecond.
That's not going to happen inside any common desktop OS
using any software solution. That includes Linux, Windows, HPUX,
openBSD, whatever. None of these desktop OS's are capable of
realtime control like you are referring to. Consequently no
software of any flavor running inside them will do the job.
If you really need miscrosecond timing you have two basic choices:
(1) use a realtime OS ( there are quite a few ), in which case
you won't be using VEE ( or labview or VB, etc).
or
(2) implement a hardware solution controlled by your application
in a desktop OS. In this case, the realtime control would
be implemented in hardware that is connected to your computer.
The VEE program would read/write data to this controller.
There's many options for buying a realtime controller
or you could build something yourself.
Desktop OS's are great for lots of things- realtime control is not
one of them.
regards
Stan
--------------------------------------------------------------------------
Stan Bischof Agilent Technologies 707-577-3994 stan_bischof@agilent.com
--------------------------------------------------------------------------
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Warren - just to clarify, what sort of length of time do you need to delay
by, and is the second command a copy of the first, just delayed?
Al.
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|"Beliveau| Document Marked as Unclassified | |
|, Bruno" | | |
|<BrunoBel| | |
|iveau@sol| | |
|ectron.co| | |
| m> | | |
|---------+-----------------------------------------------------+---------|
"Beliveau, Bruno" To: VRF <vrf@agilent.com>
<BrunoBeliveau@solect cc: VRF <vrf@agilent.com>
ron.com> Subject: [vrf] Re: Precision Timing
25/01/05
14:45
Please respond to "Beliveau,
Bruno"
Stationery name:-Untitled-
I guess that even the IO itself is not done within a time period that
accurate. Is there a way to use some external timing to trigger your
instrument?
-----Message d'origine-----
De: Pickles, Warren [mailto:Warren.Pickles@tycoelectronics.com]
Date: 25 janvier 2005 09:37
I need to send a particular command to an instrument, wait for a precise
period of time, then send another command. Problem is, this period of time
needs to be accurate to the microsecond. I imagine this is beyond the
limitations of the delay object. The delay object resolution must be a
function of the resolution of the computer's internal clock (mustn't it?).
This problem is further compounded: I am assuming that the delay between
execution of the commands is exactly the same as the delay between sending
the commands from VEE - a reasonable assumption but probably not true.
What about the "WAIT" transaction in the Direct IO object - is that any
better?
If I can't time that precisely within VEE, what options have I got? Some
external hardware perhaps?
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