Measurement Computing Personal488 rev.3.0 - Manual (Page 102)

Personal488 for Windows 95/98/Me/NT/2000 04-10-01 API Reference 6-34
OnEvent
Windows9x and Windows2000 Only !
Syntax INT WINAPI OnEvent(DevHandleT devHandle, HWND hWnd, OpaqueP
lParam);
devHandle refers to either an interface or an external device.
hWnd is the window handle to receive the event notification.
lParam value will be passed in the notification message.
Returns -1 if error
Bus States None
Example ieee = OpenName (“ieee”);
OnEvent (ieee, hWnd, (OpaqueP) 12345678L);
Arm (ieee, acSRQ | acError);
break;
See Also OnEventVDM, Arm, Disarm
The OnEvent command causes the event handling mechanism to issue a message upon occurrence of an
Arm ed event.
The message will have a type of WM_IEEE488EVENT , whose value is retrieved via:
RegisterWindowMessage ((LPSTR) “WM_IEEE488EVENT”);
The associated wParam is an event mask indicating which Arm ed event(s) caused the notification, and the
lParam is the value passed to OnEvent . Note that although there is a macro for WM_IEEE488EVENT in the
header file for each language, this macro resolves to a function call and therefore cannot be used as a case
label. The preferred implementation is to include a default case in the message handling case statement and
directly compare the message ID with
WM_IEEE488EVENT .
The following is an example of an event handler.
LONG FAR WINAPI export
WndProc(HWND hWnd, unsigned iMessage, WORD wParam, LONG lParam);
{
HANDLE
ieee;
switch (iMessage)
{
case WM_CREATE:
ieee = OpenName (“ieee”);
OnEvent (ieee, hWnd, (OpaqueP) 12345678L);
Arm (ieee, acSRQ | acError);
break;
default:
if (iMessage == WM_IEEE488EVENT) {
char buff [80];
wsprintf (buff, “Condition = %04X, Param = %081X”,wParam, lParam);
MessageBox (hWnd, (LPSTR) buff, (LPSTR) “Event Noted”, MB OK);
return TRUE;
}
}
}