[mythtv-users] Direct IR connection

Christopher Meredith chmeredith at gmail.com
Sat Apr 2 23:43:51 UTC 2011

On Sat, Apr 2, 2011 at 12:55 PM, Craig Huff <huffcslists at gmail.com> wrote:
> 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:
>        http://www.gossamer-threads.com/lists/mythtv/users/417095?search_string=Motorola%20DTA%20100;#417095
> which led me to this one:
>        http://forums.tivo.com/pe/action/forums/displaythread?postID=10435565
> 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.

Thanks, I figured it was something like this. I found that TiVo
thread, and noticed that there's a guy making these cables, like this


I'm assuming all I'd need is a blaster, such as the MCEUSB model that
seems to work so well, and this would get things going. My
Comcast-issued Cisco RNG-150 has an IR-in jack on the back, and my
understanding is that the zilog-based HD-PVR blaster can't send the
codes this STB needs.

One thing, and I may need to address this question to the seller. But
I notice that he has a few different cables for different devices. Is
this just a ebay search thing, or would different blasters really
require different types of cables?

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