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Hi all -<br>
<br>
Thought some folks might be interested to know I that I have a working
solution for controlling the channel on a Scientific Atlanta Explorer
cable box through the USB port. The model I happen to have is a 3250HD,
and I have tested it on an 8000, but I suspect it will work on any SA
cable box with a USB port
(<a class="moz-txt-link-freetext" href="http://www.scientificatlanta.com/products/consumers/index.htm">http://www.scientificatlanta.com/products/consumers/index.htm</a>). Fair
warning: this solution is relatively expensive (US$100-$180), but I
figured some people might be interested just the same...<br>
<br>
<u>Background<br>
</u><br>
After two months trying to get LIRC to control my SA cable box with
three different off-the-shelf IR transmitters, I was about ready to
give up hope. That's when I ran across an offhand comment about
somebody witnessing their cable installer using a USB keyboard to
change the channel on their Scientific Atlanta cable box. Turns out
many of Scientific Atlanta's Explorer series of cable boxes have a USB
port that allows you to change the channel with a USB keyboard. Simply
plug the keyboard in, type the digits for the channel you want and the
cable box changes the channel. Sounds simple enough, but the tricky
part is generating USB keyboard signals from your Myth box. You'd
think this would be trivial, but it's not. If you want all the nitty
gritty details, read up on how the USB master/slave relationship works
(<a class="moz-txt-link-freetext" href="http://www.linux-usb.org/USB-guide/c15.html">http://www.linux-usb.org/USB-guide/c15.html</a>). Essentially, the
problem is that both the Myth PC and the SA cable box have USB "host
controllers", and you can't have two host controllers talk to each
other directly (yes, there are such things as USB host-to-host cables,
but they're hard-wired to act like network adapters, not keyboards).<br>
<br>
So, we're left with the problem: how do we get our Myth PC to look like
a USB keyboard from the cable box's perspective?<br>
<br>
<u>Solution</u><br>
<br>
Enter the "Vetra Systems VIP-335 SmartPipe"
(<a class="moz-txt-link-freetext" href="http://www.vetra.com/335text.html">http://www.vetra.com/335text.html</a>). Essentially a protocol converter
which takes ASCII characters on its RS-232 serial input and outputs
them as PS/2 keyboard codes. Slap on a PS/2-to-USB keyboard converter,
and you've got a serial-to-USB keyboard solution. Basically any
characters you send to the serial port appear on the keyboard output as
if they were typed on a physical keyboard. This makes the channel
changing script trivial:<br>
<br>
<tt>#!/bin/sh<br>
echo `printf "%03d" $1` > /dev/ttyS0</tt><br>
<br>
I've been using this solution on my myth box for about four days now
and except for the initial connection, it has worked flawlessly. In
order to get the thing running the first time, I had to "hard boot" the
cable box (by way of disconnecting and reconnecting the power cable),
and connecting a real keyboard to the "passthru" port on the VIP-335
(and hitting a couple number keys). After that, I was able to
disconnect the physical keyboard from the VIP-335. Since then I have
rebooted the Myth box and turned the cable box on and off (by way of
the power button) many times and it has continued to work perfectly. I
suspect that I may have to go through the song and dance with the
physical keyboard again if the cable box ever loses power completely,
but I figure that isn't going to happen too often.<br>
<br>
For anyone using this as a HOWTO, I should mention that the VIP-335
ships with "data translation" turned off. Before you connect
everything for the first time, you need to turn data translation mode
on by flipping DIP-switch #4 up.<br>
<br>
<u>Costs and other considerations</u><br>
<br>
As I said, this solution can be relatively expensive. The VIP-335
sells for US$100 for the bare electronics or $150 if you want it all
packaged up in a nice black box enclosure. Add $10-$20 for a good
PS/2-to-USB keyboard converter if you don't already have one.<br>
<br>
Looking at the Vetra website I see that they are now offering what
appears to be a version of the 335 that outputs USB keyboard codes
directly (<a class="moz-txt-link-freetext" href="http://www.vetra.com/335Utext.html">http://www.vetra.com/335Utext.html</a>). This unit wasn't
available when I ordered my VIP-335, but I suspect it would serve just
as well. The USB version is more expensive than the PS/2 version ($109
for the bare PCB, $179 for the box-enclosed version), but you would
save a couple bucks by not having to buy a PS/2-to-USB keyboard
converter.<br>
<br>
Anyway, that's my solution. <br>
<br>
<u>Standard Disclaimers</u><br>
<br>
Be warned: If you try this, you do so at your own risk! I make
absolutely no guarantees of any kind. I'm not telling anybody to go
out there and buy one of these things, I'm just explaining what I did.
What you do with the information is your own affair. I am in no way
associated with Vetra Systems, Scientific Atlanta, or Earl's Pub on the
corner of 8th and Olive. No electrons were harmed in the making of
this email. Do not fold, spindle, or mutilate. Objects in mirror are
closer than they appear.<br>
<br>
<u></u><br>
- Cedric<br>
<br>
<br>
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