User's Manual

6-13
Programming Considerations
Before making any method calls, make sure you :
• Set the COM port properties (device name, baud, parity, bits, flowcontrol) as
desired. Make sure the port is closed (call CloseDevice) before 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
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 16 per base
station) is in its transaction sequence. One possible solution is to use a
"state"variable for each terminal (perhaps stored in an array). Test the state
variable to determine the next prompt for any given terminal. See the
samples for more ideas.
• 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:
1. A terminal going out of range and having its power cycled before
returning within range OR
2. Two (or more) terminals using the same ID (terminal ID conflict).