DDE Performance with AccessXP

[Jon Russell]

Hey All,

I have a problem that has be confused. I'm attempting to
write an AccessXP application that communicates using DDE
with a PLC (Programmable Logic Controller) via RSLinx
(RSLinx is a program that runs as a service and
communicates with a PLC in a shop floor manufacturing
environment).

My problem seems to be with AccessXP. Everytime the DDE
refreshes (once per second), I get a momentary
hourglass. This is a problem because I am also trying to
scan in data to a textbox with a keyboard wedge scanner,
if the operator attempts to scan while DDE is refreshing
(remember, this is once per second), their scan is either
discarded or incomplete.

Under Access XP ...
I've tried creating a form with a textbox (Text0) and set
the control source to '=DDE
("RSLinx", "MyTopic", "MyItem")' and also tried using the
DDEInitiate/DDERequest commands in the form module to
populate the textbox. Both return the requested data,
but give similar performance issues.

However, if I use Visual Basic 6.0, I don't get the
momentary hourglass, I have also written programs that
use DDE with RSLinx with Access97 which work great.

I'd really like to use AccessXP for this project, but
need to resolve the DDE performance issue before I can
proceed. Any clues or tips would be greatly
appreciated.



Thanks

Jon

 

[Arvin Meyer]

Sounds to me like you need to change the DDE refresh rate:

Tools ... Options ... Advanced tab.
--
Arvin Meyer, MCP, MVP
Microsoft Access
Free Access downloads:
http://www.datastrat.com
http://www.mvps.org/access

 

[Jon]

I've tried that, no joy ... still have the performance
issue while DDE is updating. I need to get the DDE
refresh at a minimum of once/second.

 

[Arvin Meyer]

You can try using echo off like:

DoCmd.Echo False

or

Application.Echo False

in your code to turn off the screen update, but I suspect that if you have
the refresh rate anything faster than 5 to 10 seconds you may still have the
problem.
--
Arvin Meyer, MCP, MVP
Microsoft Access
Free Access downloads:
http://www.datastrat.com
http://www.mvps.org/access