I'm trying to use an ActiveX object to read data from hardware. Certain
methods do not appear to work, specifically ones that expect a pointer to an
array of 32-bit floats as one of the variables. One method is *ReadTag*.
The C prototype is
*long ReadTag(LPCTSTR name, float* pBuf, long nOS, long nWords);*
Using MakePy, the signature is
*def ReadTag(self, Name=defaultNamedNotOptArg, pBuf=defaultNamedNotOptArg,
nOS=defaultNamedNotOptArg, nWords=defaultNamedNotOptArg):
return self._oleobj_.InvokeTypes(9, LCID, 1, (3, 0), ((8, 0),
(16388,0), (3, 0), (3, 0)),Name, pBuf, nOS, nWords)*
When I attempt to pass an array to it via:
*x = numpy.zeros(100)
obj.ReadTag('microphone', x, 0, 100)*
I get the following error:
*only length-1 arrays can be converted to Python scalars*
Alternatively:
*x = numpy.zeros(100)
obj.ReadTag('microphone', x.ctypes.data, 0, 100)
*returns a tuple and no error is raised:
*(1, 4.28, 0, 100)*
However, x is not updated with the new data from the hardware buffer.
The following does not work either:
*x = numpy.zeros(100)*
*ptr = x.ctypes.data_as(ctypes.POINTER(ctypes.c_double))
obj.ReadTag('microphone', ptr, 0, 100)*
Nor does:*
ptr = x.ctypes.data_as(ctypes.c_voidp).value
obj.ReadTag('microphone', ptr, 0, 100)*
Although no error is raised for the above two examples where I am attempting
to pass a pointer to the array, x remains an array of zeros (the microphone
is reading a 1 kHz sinusoid so x should be a sine wave). I'm a bit confused
and not sure what the best way to proceed at this point is. How do a pass a
pointer to my array into the ActiveX method?
Thanks!
Orest
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