Improve company productivity with a Business Account.Sign Up

x
?
Solved

Windows application resolution (task switching)

Posted on 2011-02-16
12
Medium Priority
?
815 Views
Last Modified: 2012-05-11
I need to send some signals to a device via USB port. The signal needs to switch from 1 to 0 every 45ms or so (the logic of the signal is a bit more complex, but we can simplify it and say that we only send 1 and 0 at every ~45ms).

As Windows is non-real time multitasking, my application will not run all the time (even if I set it as 'real time' priority) so it may not be active when the time lapses and needs to send the signal. I cannot accept a delay higher than 0.5ms. What kind of delay (jitter) I can expect from Windows?

Ignore the delay added by the USB interface/controller which is always the same. I am interested only in the delay caused by multitasking switching.
0
Comment
Question by:cubic77
  • 4
  • 4
  • 2
  • +2
12 Comments
 
LVL 3

Expert Comment

by:dmitry_n
ID: 34907016
Expect nothing.  Windows is non-real time OS. Period.
0
 

Author Comment

by:cubic77
ID: 34907076
What about the mouse driver which is pretty accurate and seems to work at milisecond precision?
0
 
LVL 32

Expert Comment

by:Ephraim Wangoya
ID: 34908439

As much as we bash Windows, it should be accurate with a figure like 45ms. (Its not like we are looking at microseconds). Unless your signalling code itself is taking more than 45ms. Even in that case, just have a timing thread that posts a message to your system to reset the signal
0
What Kind of Coding Program is Right for You?

There are many ways to learn to code these days. From coding bootcamps like Flatiron School to online courses to totally free beginner resources. The best way to learn to code depends on many factors, but the most important one is you. See what course is best for you.

 

Author Comment

by:cubic77
ID: 34908703
What about 'real time' priority?
0
 
LVL 3

Expert Comment

by:dmitry_n
ID: 34909822
cubic77, it seems. Load Windows with lots of stuff and you will see how mouse behaves.
0
 
LVL 39

Expert Comment

by:Geert G
ID: 34910378
if you want real-time (or as close as) then you need to set the level of your thread to real-time priority
and use QueryPerfomanceCounter or WaitForSingleObject or something like that for the trigger

the mouse is set in a high priority thread, that's why it responds so fast
0
 

Author Comment

by:cubic77
ID: 34910420
@Geert_Gruwez
Thanks Geert.
So it can be done.
0
 
LVL 39

Expert Comment

by:Geert G
ID: 34910432
you can get close, but probably no garantee
you need a plc for something very accurate
0
 
LVL 39

Expert Comment

by:Geert G
ID: 34910436
something like a anti-virus can really mess up such a system
0
 

Author Comment

by:cubic77
ID: 34910458
>you need a plc for something very accurate
Ya, I imagined that. I was thinking actually to a small board with a microcontroller. I just wanted to know what I can expect from a Windows app.
0
 

Expert Comment

by:SleekProductions
ID: 34924377
Like Geert_Gruwez says thread handling is probably needed. I curious as to whether one would gain anything by writing a service (and then optionally communicating with the service if an GUI is needed).
0
 
LVL 39

Accepted Solution

by:
Geert G earned 2000 total points
ID: 34924412
most of this is explained here:
http://en.wikipedia.org/wiki/Real-time_operating_system

lately most windows like xp are preemptive scheduling

differences can be found here :
http://en.wikipedia.org/wiki/Co-operative_multitasking

0

Featured Post

Get your problem seen by more experts

Be seen. Boost your question’s priority for more expert views and faster solutions

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Today, unlike web development, the mobile landscape is complex enough for a software engineer and Android is posing more challenging environment thanks to its fragmentation issues on hardware and software fronts.
Article by: Shaun
Tiling windows is a great way to see multiple applications at once. Windows Tiler is a tool that automatically tiles open application windows as the open and close.
In this fifth video of the Xpdf series, we discuss and demonstrate the PDFdetach utility, which is able to list and, more importantly, extract attachments that are embedded in PDF files. It does this via a command line interface, making it suitable …
Starting up a Project

606 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question