MythTV and Directv (was Re: [mythtv-users] MythTV and DISH - a great solution)

John Gruenenfelder johng at
Thu Sep 23 17:37:21 EDT 2004

On Thu, Sep 23, 2004 at 02:08:41PM -0500, Rob Fugina wrote:
>On Thu, 23 Sep 2004 11:39:09 -0400 (EDT), Eric Joe <sysop at> wrote:
>> > Many of the Directv receivers have the low-speed serial port mentioned
>> > (especially RCA).  I have the RCA DRD435RH Directv receiver and made my
>> > own serial cable using instructions from with
>> > the external channel changer script from
>> > .  Solid channel
>> > changes.  Never had a problem.
>> I have been running my Mythbox for about 9 months with DirecTV. I also
>> made a serial cable for my RCA receiver. It has a little jack that looks
>> like a phone jack labeled Home Control. I had been using an old Sony
>> receiver that uses a standard DB9 serial connector. Both worked fine.
>Same serial protocol, eh?  I've been wondering, since the and
> files I've found seem to be pretty much identical.  I have a
>fairly old Sony (5 yrs?) that has worked fine with  the that I
>found.  I'm planning on expanding my backend to two PVR250's, and I'll
>need an additional DirecTV recieiver, but the only plain-and-simple
>receiver I can find is non-branded (or DirecTV-branded).  I've been
>wondering if the serial protocol on this device will be the same as
>the Sony and RCA models.  Anybody know?

There is a fair amount of info about the protocols available online, but
sometimes it can be a little contradictory.

To the best of my knowledge, there are three protocols typically used.
  1) Older Sony
  2) Older RCA
  3) New Sony/RCA

Unfortunately, I don't really have a good time frame for when devices started
using the new protocol.  It seems that, to make life easier for third parties
like TiVo, the receiver companies agreed on a single new protocol to remove
any confusion.

I've had my RCA receiver since Spring of 2004 and it uses the new protocol.
Most of the scripts I found were for the two older protocols and had more
abilities, while the script for the new protocol was very minimal.

I combined a working new protocol script with some misc. abilities, like
clearing the OSD right after a channel change and created the script linked
above.  Though it's titled "rca", if anything I've said is actually true, it
ought to work for newer Sony models and maybe others as well.

--John Gruenenfelder    Research Assistant, Steward Observatory, U of Arizona
                        johng at
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