Phytec eGrabber-4plus, Руководство по оборудованию

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Driver Software

PHYTEC Meßtechnik GmbH 2004 L-608e_4
137
You can monitor this event by using the Windowa API-function
WaitForSingleObject(). Please note, that the event has to be reset by
calling the function ResetEvent(). Otherwise, new events can not be
signaled.
Important:
•
The event is signaled every time the digitizing of a field is finished.
This happens only, if the digitization has been started
(Start_Grabber() ). After the occurrence of the field end, the signal
remains active until it is reset by calling ResetEvent(). This enables
the application software to determine event some time later,
whether the event had happend or not
To reset the event, the function ResetEvent() must be called.
Otherwise, the next call of WaitForSingleObject() would return
immediately, because the signal is still active.
ActivateFieldInterrupt() should therefore be called only when the
grabber is not running. It might be advisabe to call ResetEvent()
after that, to reset any older active signals, which might have been
created in the meantime.
•
To determine, which field had been digitized, the DataPresent() –
function should be called immediately after the event had been
signaled. In case of continuos digitization this is done by
evaluatiing the state of the
T_EVEN
/
T_ODD
– flags. Care must be
taken to read out this flags immediately, because their state will
only persist for 20 after the end oft the field. (This is, because 20
ms later, the next field digitization is completed and therefore the
flags are updated).
Hint: An exclusive-or – combination of
T_EVEN
and
T_ODD
will
result the parity of the field (1=ODD, 0=EVEN):
field_ready
:=T_EVEN ^ T_ODD;
•
The event is created by the grabber driver with a very short time
delay. Please notice, that the delivery to the applicatin by the
operation system might last a noticable (and variable) time.