[mythtv-users] Scientific Atlanta 3250 - Anyone get this to work with LIRC/MythTV

[Alan Carlson]

Searching old posts, there appears to be a well documented problem with
the sa3250 Digital Cable set top box that Time Warner (and others?) are
using. Has anyone got this to work with LIRC using a ir blaster?

When googling the web, I found the Audioplex web site that talked about
the problems their IR repeaters had controlling the Scientific Atlanta
Models 3100HD, 3250 and 4200. Here's the text of the pdf:

Installers have noticed problems with the Scientific Atlanta models
3100 HD, 3250 and 4200 Series responding to IR repeater systems,
especially installations with plasma screens. These units should operate
at the 56 KHz IR frequency but seem to have some variations in
frequency.

The X4056 dual processor IRTarget from Audioplex will perform well with
the variable frequencies and the Plasma-Proof IRtargets are the best in
the industry for consistent operation with plasma screens.

It has been also been discovered during testing that the above
Scientific Atlanta units are very sensitive to IR signal strengths and
are easily overwhelmed and will not operate if the signal is too strong.
Installers have found that rather than placing an individual emitter
directly over the Scientific Atlanta IR sensor, it works better if the
unit receives signals from an appropriately placed IRFlood or even from
the reflected signal of emitters placed on nearby components within the
cabinet.

The technical department at Audioplex Technology has worked out a
wiring modification of it's standard setup to allow an emitter to be
placed on the Scientific Atlanta IR sensor. See the diagram to the
right. 

If you want to go see the pdf, go to 
http://www.audioplex.com/technotes.htm 

The web site sent the tech note to my browser as a .htm instead of a
.pdf file. So get this pdf to open right click on the "001: Scientific
Atlanta IR problems" link and Save As to save it to disk. It saves it 
as TECH001.htm, rename TECH001.pdf and open it.

I was also reading some other documentation on the site, and apparently
these SA boxes use a different IR Frequency band. The "normal ir band"
is the 40k Standard Band. It is the industry standard carrier frequency
of IR remote controls and is between 32 and 44 kHz. 

There is a 56k Standard Band, that is designed to work with RCA-DSS,
General Instrument, Motorola, Scientific Atlanta and ProScan equipment,
as well as many new Digital Cable and Satellite Receiver boxes at 56
kHz.

Could this be the root of the problem with LIRC, or a combination of
the 56k IR band and the problem with overwhelming the IR receiver?




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