I'm not sure if I am hearing you correctly, but this sounds similar to what I'm doing, correct me if I'm wrong.

I have a MythTV Box->usb->serial cable ---> MAGIC WIRING ---> serial->usb->DirectTV STB

And I use the directtv.pl script to change the channels over usb. 

If this is what your going for let me know, and I can get you some more detail.  Also I can get you a schematic for the wiring that I use.

On Fri, Mar 6, 2009 at 6:49 AM, Marius Schrecker <marius@schrecker.org> wrote:
Hello,

    I am wondering whether there is any way of emulating a usb blaster by connecting two devices directly using a USB bridge cable.
I would like to connect my MythTV box to my Set Top Box's USB interface, emulating an external USB dongle on the STB.

 Does anyone know if this is possible?


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