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- Path: cc.newcastle.edu.au!outias
- From: outias@cc.newcastle.edu.au
- Newsgroups: comp.lang.c++
- Subject: Help: About VXDs?
- Date: 22 Feb 96 19:19:51 +1100
- Organization: University of Newcastle, AUSTRALIA
- Message-ID: <1996Feb22.191951.1@cc.newcastle.edu.au>
- NNTP-Posting-Host: cc.newcastle.edu.au
-
- To anybody in the know,
-
- I have an Windows application I need to write which communicates
- serially to two external devices. I have a proprietary DLL which
- has all the functions I need for communications.
-
- My problem is I need to have a precise timing sequence. One device
- takes about 10ms to obtain a message (its only small). The other
- device takes about 270ms (its quite large). I need to get a message
- from both devices before I can do anything with the data so the
- complete cycle is say 300ms. I need to guarantee that I get data
- from the devices each 300ms cycle without fail. I can hog the CPU
- and get the data in the time required but the old hold the mouse
- button down on a window title trick kills everything.
-
- Windows being the non deterministic operating system that it is
- makes it quite difficult to guarantee anything. Timers are
- virtually useless. They do not guarantee anything and are certainly
- erratic when trying to do anything real time.
-
- I thought maybe a VXD device driver may cure my problem but I have
- no knowledge of these whatsover. My questions are these :
-
- Is writing a VXD the way to go?
- Is it as daunting a task as it sounds?
- If I do write a VXD can I incorporate the DLL calls to control the
- device?
- or do I need to source code for the DLL to build it into the VXD?
- Can anyone recommend some books, sample code, FTP sites whatever
- where I can get some info to speed development?
-
- Thanks in advance.
-
- AJAY
-
- PS. Sorry about the bullshit characters but I edit this on a PC and
- send it through a VAX account.
-