ASCOM driver problems

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rwg
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ASCOM driver problems

Post by rwg » Tue Apr 12, 2011 5:40 pm

Hi,

I'm the author of SharpCap (http://www.sharpcap.co.uk), an Astro capture application. One of my users has been trying to get an FCUSB focuser to work with Sharpcap using the ASCOM driver without any success. This evening I downloaded the driver installers myself and was able to reproduce the same problem - the COM object FCUSB.Focuser gets created successfully, but the QueryInterface for the ASCOM IFocuser interface fails.

A bit of digging led me to this - the IFocuser interface defined in the AscomMasterInterfaces.tlb typelib has a GUID of C2E3FE9C-01CD-440C-B8E3-C56EE9E4EDBC, whereas the typelib inside FCUSB_ASCOM.dll has an interface called _Focuser with a GUID of 5BD94F3E-037B-422C-B439-A1F7246E85A3. Even though the two interfaces have the same sets of methods on them, as far as COM is concerned they're unrelated to each other, which explains my initial problem with getting the IFocuser interface. (You can see the same info by opening the typelibs and dll with the 'oleview' tool that comes with Visual Studio or can be downloaded here : http://www.microsoft.com/downloads/en/d ... laylang=en).

So, as far as I can tell the incorrect GUID for the IFocuser interface is the root cause of the problem here - It seems likely that currently the interface will only work for clients that use late binding via IDispatch (VB6 etc) to call methods because the method names and parameters are the same. For applications using early binding via the type library (C++, C# etc) I expect that nothing will work.

Is there any chance that you could update the focuser driver to fix this issue? I can provide sample code in C++ or C# that demonstrates the issue if that is helpful and test any updates. I also (for my sins) do a fair bit of COM programming in my day job, so I am quite willing to work with you to try to build a fix.

cheers,

Robin

ps. I tested the FCUSB2 ascom driver too - it has the same issue of having its own interface GUID instead of using the one defined in the AscomMasterInterfaces.tlb

riya
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Re: ASCOM driver problems

Post by riya » Tue Jul 30, 2013 11:24 pm

Glad to hear about your setup, sounds like you have quite the system. I have quite a few other projects on my plate right now, so I don't think I could get to an FCUSB3 anytime soon. However, you could use the JMI PCFC as a third focuser controller!
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