Anyone have any experience with the CommEvent in the MSComm control
(VB5 - SP3)? Specifically, what could generate a spurious CommEvent
value of 6? (CommEvent 6 is "Ring Detected").

From what I've been able to learn so far, a signal on pin 22 of an
RS232 port indicates a Ring Detected; some UARTs pass this through;
I'm guessing this is what would show up in the MSComm control as
CommEvent #6.

The trouble is, in my app there is no RS232 (I'm using RS422), there
is no pin 22 (using DB9's) and there are no phones involved
(therefore, no ring signals).

Anyone ever run into anything like this? Any ideas or thoughts will be
appreciated.  Thanks.

Hi Martin,

The comRing event is not generated reliably.  IMO, you code should ignore it
completely.  If you want to detect ringing, add code to your OnComm event
the parses modem responses and looks for the "RING" message.  This is
generated reliably.

In your case, simply ignore that CommEvent.

(Btw, the source probably is faulty hardware -- the ring line from your
RS-422 converter is floating, not held at a high or low state, thus the UART
sometimes picks up noise on that line and generates an interrupt that the
Windows serial driver passes on.)

--
Richard Grier (Microsoft Visual Basic MVP)
Hard & Software
12962 West Louisiana Avenue
Lakewood, CO  80228
303-986-2179 (voice)
303-986-3143 (fax)
Author of Visual Basic Programmer's Guide to Serial Communications, 2nd
Edition ISBN 1-890422-25-8 (355 pages).
For information look on my homepage at http://www.hardandsoftware.net.
Use the Books link to order.  For faster service contact the publisher at
http://www.mabry.com/vbpgser.

Dick -

Thanks for your response.

My code does ignore that CommEvent (except that I'm logging the fact
that it occurred to an event log - which bothers the user - I may
discontinue it). I'm more concerned that it might be causing problems
with the receipt of data (CommEvent = 2). What are your thoughts on
that?

On occasion, I lose ALL serial communication - data (from several
barcode scanners coming in through a multiplexer)  just stops coming
in. If my program is shut down and restarted then everything is fine -
until the next time. I don't know if this has anything to do with
spurious Ring Detected event or not.

I have 20-25 installations with this code operating. One location is
experiencing this problem - and it's happening on two different
computers at that location.

On Wed, 29 Nov 2000 09:31:00 -0700, "Dick_Grier"

Dick -

After posting my previous reply I re-read your message again and
thought of another question. you mentioned my "RS422 converter".
Actually, I'm not converting anywhere. The scanners are transmitting
in RS422 to a Baytech multiplexer which in turn is connected to one
line of an RS422 Digiboard. Any thoughts as to a likely culprit in
this chain of equipment? The Digiboards have been swapped out with no
apparent improvement in the problem. I just got in a new Baytech that
I haven't tried yet.

Thanks

Martin

On Wed, 29 Nov 2000 09:31:00 -0700, "Dick_Grier"