[mythtv-users] Nvidia ION unreliable HDHR Prime at gigabit speeds

Gary Buhrmaster gary.buhrmaster at gmail.com
Sun Feb 28 03:14:57 UTC 2016


On Sun, Feb 28, 2016 at 2:23 AM, Will Dormann <wdormann at gmail.com> wrote:
....
> I see now that my cable box has what appears to be a 3.5" jack called
> "IR Remote Input".   Which I would assume the MythTV box can perhaps
> control w/o IR anywhere in the chain, right?  i.e., serial to serial.

Well, "simulated" IR blaster to "simulated" IR receiver (with
no actual IR (except inside the IC) involved).  You still need
a "blaster" which accepts a plug for the emitter itself, and then
plug the output into the IR in port.  Sometimes you can use
a serial output port of your PC, and sometimes you want a
"real" blaster to meet the tolerances of the receiver (I had
used both an iguanaIR and the commandIR for my "blaster"
in a previous life).

> Or is the opto-isolator used because the IR Input port isn't designed to
> be electrically connected to another system, due to ground loops or
> whatnot?

Right, potential ground (loop) issues.  While "usually" it
will work sharing ground, I am a bit on the paranoid side,
so designed a circuit which shared nothing.  Many others
have done equivalent solutions (what I did is not special).

There are a lot of solutions out there (if you look around
for (old school) TiVo to DTA/STB direct connect cables
in the usual places).

>  Either way, do you have any links to your contribution to the
> wiki?

For the lirc channel changer script, I submitted/used this:
https://www.mythtv.org/wiki/LircChannelChanger

For the opto-isolator, I documented this at:
https://github.com/garybuhrmaster/misc/tree/master/IR_Blaster_to_Comcast_DTA_direct_connect_cable
(I did not add it to the mythtv wiki since I figured it was
too specialized).

In any case, as long as firewire works for you, I would
not touch it.  Just keep the idea of alternatives in your
toolbox for future use.


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