[mythtv-users] Using USB to change channels on cable box?

Bruce Markey bjm at lvcm.com
Wed Aug 15 17:27:11 UTC 2007

Christopher Robbins wrote:
> I've got a Scientific Atlanta 3250 (non-HD) cable box...It's got a
> USB port or two.  Is there any way to control the box via USB?  I've

There is one USB port on the front that does recognize numbers,
Enter and ESC from a USB keyboard. If you plug a keyboard in
you will see that you can change channels with it although I
don't know if it supports any other remote control keys. So,
it could be used but I don't know if a USB crossover cable or
serial to USB or whatever could be connected and I don't know
if any software exists that could send keycodes out to a remote
USB device. If you come up with a solution, post it here.

> read a lot about using firewire with the 3250HD, but nothing about
> the standard def box.

Then go with the flow =). I recently decided to exchange my
3250s for 3250HDs just to try the firewire channel changer.
If you don't have an HDTV set, this seems unnecessary but it
turned out to be a Good Thing.

The HD model is backward compatible with the 3250 so you can
use it as a Digital Cable box without ever using HDTV. It has
additional outputs for component, DVI and ieee1394 firewire.

Following the ./contrib/channel_changers/sa3250ch-README was
easy and I had no problem getting this to work and so far it
has been 100% reliable (when the kernel modules are loaded
and the cable is seated properly ;-).

There was a big bonus surprise. Obviously, this box can decode
HDTV channels. What I hadn't anticipated was that it downscales
these to NTSC (480i) and sends them out the s-video port(!) and
presumably composite and coax too. This meant that I could now
get my local HD channels, cable stations like TNTHD, ESPNHD
and ESPN2HD, HD versions of HBO, Showtime and CineMAX, plus
entirely new channels of content from Discovery HD Theater,
MOJO, Universal HD and PBS-HD.

There is also the possibility of firewire capture but I haven't
gotten this to work yet and it would raise issues that are
supposed to be addressed by input groups. However, this opens
the possibility of capturing MPEG files directly from another
virtual 'capture card' with no physical tuner card.

While the resolution is still standard def and these channels
are letterboxed, the clarity and accuracy are still a win for
ESPN* vs analog broadcast and I also schedule several shows that
I only get from HD channels. I highly recommend asking your cable
company if you can exchange your box for a 3250HD for anyone with
a 3250 or any other standard def box.

> Would it be easier to use an IR blaster?

IR blasters can be unreliable by missing or doubling numbers.
Hard wired is the way to go if at all possible.

Another possibility that I've done before is to set your channel
change command to /bin/true and use the 3250 built in VCR timers.
Press "Settings" twice and the "New Timer" allows you to manually
schedule a channel change or you can add them from the EPG. This
too is 100% reliable (when you pick the right date and set am/pm
correctly ;-).

--  bjm

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