Seth Sims wrote:
> Hello everyone,
>
> I am having a problem receiving events from some com objects I am working
> with. win32com has performed beautifully so far
> and the code can call methods and manipulate properties with no problems.
> However I cannot seem to figure out why I am not
> receiving events. It is probably just a lack of knowledge on my part about
> com but thats why I am asking.
> The com object that this code accesses follows a specification for
> talking to point of sale devices called OPOS. In
> particular it is a control for a magnetic stripe reader device. I need to
> receive the DataEvent event from the control. I am
> using the method prototypes from the makepy utility for the event class but I
> never see their print statements executed on my
> output.
> The DataEvent is being fired though the various card properties are not
> filled in until the event is generated and those
> show up every time. Also I have used the ActiveX test shell from vc++ 6 and
> it receives the events. In the output I have
> scrubbed the card number and name (its actually a fake test card but it seems
> safer this way) but the data is there and
> correct. Thank you for your help in advance.
>
> -Seth Sims
>
>
> -----------event.py-------------
>
> import win32com.client as client
> import pythoncom
>
> class OPOSEventSink:
>
> def OnDirectIOEvent(self, EventNumber, pData, pString):
> """method DirectIOEvent"""
> print "direct io"
>
> def OnDataEvent(self, Status):
> """method DataEvent"""
> print "data"
>
> def OnStatusUpdateEvent(self, Data):
> """method StatusUpdateEvent"""
> print "status update"
>
> def OnErrorEvent(self, ResultCode, ResultCodeExtended, ErrorLocus,
> pErrorResponse):
> """method ErrorEvent"""
> print "error"
>
>
> if __name__ == '__main__':
> msr = client.DispatchWithEvents("OPOS.MSR", OPOSEventSink)
>
> #Ready the device
> msr.Open("Ing6XXX")
> msr.ClaimDevice(-1)
>
> #setup the magnetic stripe reader
> #tell the device to turn its self off when a swipe is read
> msr.AutoDisable = True
> msr.DataEventEnabled = True
>
> #read all 4 tracks
> msr.TracksToRead = 0xf
>
> #hold events till I tell you to send them
> msr.FreezeEvents = True
>
> #turn the device on
> msr.DeviceEnabled = True
>
> print "please swipe a card"
>
> #when this loop finishes there has
> #been a successful swipe of a card
> #and a data event is waiting to be
> #released in the com object
> while msr.DataCount < 1:
> pass
>
> #by the OPOS specification these
> #attributes are set as blank strings
> #until a data event is fired
> print 'before unfreezing events should be blank'
> print 'Account number:', msr.AccountNumber, \
> '\nName:', msr.Surname, '\n'
>
> #release the events
> msr.FreezeEvents = False
>
> print 'events thawed should still be blank'
> print 'Account number:', msr.AccountNumber, \
> '\nName:', msr.Surname, '\n'
>
> pythoncom.PumpWaitingMessages()
>
> print 'after pump waiting messages now the values should be there'
> print 'Account number:', msr.AccountNumber, \
> '\nName:', msr.Surname, '\n'
>
> msr.ReleaseDevice()
> msr.Close()
>
> ---------- Output -------------
> please swipe a card
> before unfreezing events should be blank
> Account number:
> Name:
>
> events thawed should still be blank
> Account number:
> Name:
>
> after pump waiting messages now the values should be there
> Account number: <scrubed by me>
> Name: <ditto>
It may be that a single PumpWaitingMessages doesn't allow enough
time for the events to be delivered. Try running it in a loop with a
small sleep until the event is fired.
Roger
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