Worth Data 701 RF Owner's Manual download pdf (Page 48)

Chapter 7:

PromptCOM/ActiveX

Drop-in components are tools that are added to your programming environment "tool kit". There are a variety of different tech-

nologies around for implementing a drop-in component such as VBX (for Visual Basic) and VCL (for Delphi and C Builder) and

COM (ActiveX). Only the ActiveX variety are widely compatible with almost all development environments.

PromptCOM/ActiveX is a drop in COM component that allows programmers to easily add the ability to send prompts to and re-

ceive data from their RF Terminal via an RF Base Station. It is compatible with Visual Basic, Visual C++, Delphi, and most other

32-bit development platforms. See the help file for installation instructions.

Programming Considerations for ActiveX

Before making any method calls, make sure you :

 Set the COM port properties (device name, baud, parity, bits,) as desired. Make sure the port is closed (call CloseDevice) be-

fore making changes to any of the port settings.

 Call the OpenDevice method. This activates the COM port used by this instance of the WDterm control.

 Set the ActiveTerminal property to identify the terminal on which you desire to operate. You can change the ActiveTerminal at

any time in order to direct commands to appropriate terminals.

Test For Good Communication – ActiveX Object

Implement an event handler for OnTermBaseRegister that causes a beep or displays a message when called. If communication

between the host PC and the base station is good, your event handler will fire when your program is running and you power up an

attached base station.

Multiple Base Stations

For installations using multiple base stations attached to a single host PC (these were called "channels" in PromptCOM/DLL) simply

add a WDterm control to your application for each base station.

Terminal Tracking

Since you get one set of event handlers for each base station, you will need some scheme for keeping track of where each terminal

(up to 64 per base station) is in its transaction sequence. One possible solution is to use a "state" variable for each terminal (per-

haps stored in an array). Test the state variable to determine the next prompt for any given terminal. See the samples for more ide-

as.

It is very important to keep track of "login status" for each terminal. Every SignOut event should have an associated SignIn event

and a given terminal should not be allowed to SignIn twice without an intervening SignOut. Multiple SignIns from one terminal

without appropriate SignOuts indicate either:

A terminal going out of range and having its power cycled before returning within range OR

Two (or more) terminals using the same ID (terminal ID conflict).

Concepts - ActiveX Object Programming

When you use drop-in components in your program you will follow the standard object-oriented programming paradigm that uses

properties, methods, and events to implement the functionality of the drop-in component.

 Properties are the various configuration variables used by the drop-in component. An example of a property is the ComDevic-

eName setting.

 Methods are function calls used to issue commands and access features of the drop-in component. An example of a method is

sending an Input command to the terminal.

 Events are function definitions placed in your application’s source code. The function definitions in your source code are called

Event Handlers. The skeleton structure of the event handler’s source code is automatically generated. The code in the Event

Handler is called ("fired") by the drop-in component when a specific event occurs. An example of an event is when a terminal

returns data and the OnTermData event is fired.

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Worth Data 701 RF Owner's Manual Page 48