Newsgroups: comp.robotics
Path: brunix!uunet!utcsri!torn!newshub.ccs.yorku.ca!newshub.ariel.yorku.ca!cs911225
From: cs911225@ariel.yorku.ca (KEN E WILLMOTT)
Subject: Re: IR remote timing
Message-ID: <1992Dec22.171631.13996@newshub.ariel.yorku.ca>
Sender: news@newshub.ariel.yorku.ca (USENET News System)
Organization: York University, Toronto, Canada
References: <1992Dec21.165153.1282@newshub.ariel.yorku.ca>
Date: Tue, 22 Dec 1992 17:16:31 GMT
Lines: 69

Hi,

Hate me if you like, but I posted erroneous data about infrared
remotes, and I thought it would be better to repost, so I fixed
the figures and added info about the continuous key mode.

I found the postings about the Sony infrared remote control
protocol interesting, but I was alarmed to note that it did
not seem to mesh with the readings I got from 3 different
controls in use in my living room. These are an RCA t.v.,
an Onkyo receiver, and a Jerrold tuner.

Here is what I found (presence of signal = logic 1):

First, there is an AGC stabilization pulse, followed by a short
break. Then come the mysterious bit patterns (I'll get to them).

Signal			Duration	Polarity
------			--------	________

AGC pulse		9.15 ms		1
pause			4.33 ms		0
50 3-bit patterns	1125 us		(see below)

Each 3-bit pattern consists of three 375 us. long bits.
The first two are always the same, and convey the binary
information. The last is always set to 0.

When these bits are laid out end to end, they look like
the following (actual data from one of my controllers):

11 01 11 01 10 10 10 11
01 01 10 10 11 10 10 10
10 11 11 01 11 11 01 01
01

There are two interesting features of this stream, neither
of which I am sure is always true, or merely an artifact
of the particular button I chose.

1) The pattern 00 never appears
2) The pattern 10 never precedes the pattern 01

Note that this can't be what I believe is called Manchester or
simple phase encoding, because of the presence of four con-
secutive ones. My grouping of bits into pairs is only based
on a gut feeling, and may be a red herring.

When some keys are held down continously, a different type of
packet is sent. It looks like this:


Signal			Duration	Polarity
------			--------	________

AGC pulse		9.15 ms		1
pause			2.10 ms		0
stop pulse		750 us		1

time until
next packet		38.6 ms		0


As I have said before,
if anybody out there has more information to add to this,
I would be eternally grateful.

	-Ken

