Programming instructions

WaveRider Operating Manual

155

APPENDICES

WHAT IS DDE AND THE DDE SDK?

The WaveRider DDE SDK consists of WWDDE.DLL and its associated header file and

export library. Functions within the DLL allow a Windows application to easily establish a

DDE link with WaveWare, over which the application can obtain data from WaveWare either

through callback functions (DDE hot links) or by query (DDE cold links). Additionally, the

application can execute WaveWare before linking with it, close WaveWare when it is

finished, and perform a variety of control functions which affect WaveWare's operation.

Using WWDDE.DLL, a single application can connect with multiple instances of WaveWare

(which in turn operate WaveRiders on separate serial ports). Multiple applications can

simultaneously connect to a single instance of WaveWare. In the future, links may be able to

be established over a network, using the NetDDE protocol under Windows 95.

The philosophy guiding the design of this SDK points to the creation of a very simple, easy-

to-use interface to WWDDE.DLL. In order to create a system involving biological signals,

the configuration of WaveWare itself must be created. For example, WWDDE.DLL makes it

easy to connect with WaveWare's General Graphics windows, but the DLL does not provide

for configuring of those windows. If it did, the DLL and SDK would be extremely

complex, and would change continually as WaveWare grew. Our philosophy is to avoid this,

giving developers a robust, powerful interface which can be learned in a short time and used

on a high level.

At present most of the data links with WaveWare are implemented as DDE (Dynamic Data

Exchange) conversations, with WaveWare as the server and WWDDE.DLL as the client.

While it would be possible for an application to bypass WWDDE.DLL and create its own

DDE conversation with WaveWare, this is not recommended. First, DDE is not a trivial

exercise, and a great deal of bookkeeping and error handling is provided by WWDDE.DLL.

Second, the DDE protocol used by WaveWare is not published, and is subject to change,

while the DLL shields the application from this protocol. Third, DDE may not be the only

form of interprocess communication to be used in the future, as both WaveWare and

Windows continue to evolve.