[mythtv-users] Direct IR connection

Craig Huff huffcslists at gmail.com
Sat Apr 2 17:55:42 UTC 2011

On Sat, Apr 2, 2011 at 11:37 AM, Christopher Meredith
<chmeredith at gmail.com> wrote:
> Hi Craig,
> I saw you mention on the Mythtv list that you are directly controlling
> a Comcast STB using an IR cable. Would you mind sharing your setup?
> I'm trying to accomplish the same thing. Thanks!

Christopher and anyone else interested:
My answer has two alternatives.  I'll cover both. ;-)
Then note the "software" setup at the end.

A) For DTAs that have a stereo jack for use with a remote IR receiver:
 (STBs usually don't have this, so skip down to B) if this is what
you're interested in.)
I found this thread:
which led me to this one:
and built my own cables on the theory that anything that worked for a
TiVo, MythTV can do better! ;-)

I just bought 4N37 optoisolators from Digikey, mono patch cables,
stereo patch cables, and heat shrink tubing from Radio Shack and went
to work.  The biggest challenge was that I bought standard DIP
packaged 4N37s and had to bend the leads out flat with the bottom of
the package as if they were flat pack parts (without breaking the
leads off).  Next time I might look for "from the factory" flat pack
parts, assuming the leads aren't spaced closer together.  If the leads
are closer spaced on the flat pack it would be necessary (for good,
reliable construction) to insulate each connection so they don't short
against one another.  I didn't need to deal with individual lead
insulation with the 0.1" spacing DIP leads since they were stiff
enough for the separation distance to not be a concern.  I just put
heat shrink on one of the half-cables, soldered everything together
per the cited articles, slid the heat shrink over the 4N37 and exposed
solder connections and put it in the toaster oven (WITH CLOSE
ATTENTION!)  Don't leave it in until the heat shrink is "done" or it
will be overdone. ;-)  Better to have to "toast" some more than too
much and melt the cables.

B) For STBs which don't fit the above description, many, including my
Motorola DCT2524, have a DB-15 serial port on the back.  Just use a
serial cable to connect it to a serial port on your MythTV backend.

Once the hardware is connected, you can find good advice in the MythTV
wiki on how to control the tuner boxen from MythTV.

Realize that the DTA cable is just a combination of the blaster LED
and the DTA photocell in the optoisolator (e.g. 4N37) with the
appropriate wires leading to the two ends -- mono connector to the
blaster and stereo to the DTA.


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