Re: serial communication

From:

"Ben Voigt" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 19 Apr 2007 10:57:06 -0500

Message-ID:

<#5QuQupgHHA.4260@TK2MSFTNGP03.phx.gbl>

"Tom Bruyneel" <tombruyneel@freedownloads.be> wrote in message
news:40154666-274A-4414-A98A-32D5DC3F2E0F@microsoft.com...

I changed it to one byte instead of a buffer hoping i would find the
solution
to my problem. I've changed it back to a buffer now. But that leaves me
with
the problem that on some pc's (my intel laptop has no problem, my amd
desktop
has the problem) changing the ReadTotalTimeoutMultiplier to 2 ms (for one
byte) would time out to soon. Maybe i don't understand the values
correctly.
Aim I right in thinking the following:

ReadIntervalTimeout: timeout between receiving of two bytes once a byte
has
been received
ReadTotalTimeoutMultiplier: multiply with the size of your and add
ReadTotalTimeoutConstant

so lets say i get a message from the external device which starts with
0x02
and ends with 0x03 and two CRC bytes and I wont to make sure every
character
is followed by another one within 2 ms. I would take the values like

ReadIntervalTimeout: 2
ReadTotalTimeOutMultiplier: 2
ReadTotalTimeOutConstant: 0

However, this doesn't work on some machines, i have to take a
ReadTotalTimeOutConstant of 16 ms or higher to make it work as expected.
Such
a value doesn't allow me to detect inter character timeouts of 2 ms. What
aim
I doing wrong?

You aren't understanding the timeouts right. You will timeout either
ReadTotalTimeOutConstant + N * ReadTotalTimeOutMultiplier ms after the call
to ReadFile (hence the "Total") or ReadIntervalTimeout after the last
character.

Set ReadIntervalTimeout to the maximum permissible delay between bytes in a
message.
Set ReadTotalTimeOutMultiplier to 0.
Set ReadTotalTimeOutConstant to the maximum permissible delay between
messages.