[mythtv-users] D11-100 USB Connection!

Jeff Simpson jeffsimpson at alum.wpi.edu
Tue Aug 29 19:28:48 UTC 2006

On 8/29/06, John Pierce <john.j35 at gmail.com> wrote:
> I have a new D11-100 Directv receiver, the one the with the usb port,
> I am curious why all of the posts are using a usb->serial adapter.  Is
> there some reason why it cannot be connected via a usb port on the
> computer. I have not plugged the box into my myth machine yet, and I
> am curious as to wether it will destroy it if I plug it into the usb
> port?  Is it just a programming issue with the usb port sending
> commands to the box?  Is it remotely possible to try to control it
> from a usb port?

The STB is basically a very simple computer with a USB host on it.
That host is looking for a device to connect to it, specifically, a
USB->Serial device. While a computer can accept any device you throw
at it, so long as that device has a driver available, a STB can only
accept what devices were coded into the firmware.

USB is not simply a fast serial line, it is a complex system that
requires devices and hosts to identify themselves to eachother (this
is what allows you to have USB hubs - you can't share a normal serial
port like that)

You could technically (somehow) find a usb cable that was male on both
ends (I doubt they exist - most USB cables are different on each end
so that it is clear which end goes to the computer and which end goes
to the device). If you plugged it in, though, nothing good would
happen. The STB would be waiting for a device, as would the computer.
Since there is no spec for how to just straight-connect two computers
together with USB, at worst case there is a good chance that however
you decide to do it could end up shorting the power between them and
cause permanent damage to either or both ends. Best case is that
nothing at all will happen.

You can, however, use TWO USB->Serial converters to connect the USB on
the STB to the USB on the PC, so long as you have a null modem
cable/adapter between them. I don't know that anybody has actually
done this yet, but I see no reason why it is not possible.

I hope that clears up some of your confusion and answers your question.

- Jeff

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