JP1 Remotes

3FG · Expert Joined: 19 May 2009 Posts: 3367

One other point, which Rob may be able to answer. I guessed at the order of the phases. Probably 0 = <-2,2> is correct, but I didn't decode all the signals to see if the OBCs made sense. Is a different order of the 4 phases more likely to be correct?

The Robman · Posted: Tue Mar 06, 2012 5:13 pm Post subject:

vickyg2003 · Posted: Tue Mar 06, 2012 5:13 pm Post subject:

The Robman · Posted: Tue Mar 06, 2012 9:41 pm Post subject:

Well, with a normal quad, you're alternating between 4 normal pairs (and by normal, I mean they're ON-OFF pairs). I don't recall if it's possible to send a pair reversed (ie, OFF-ON) when you're doing it manually. I think you'd have to send the ON and the OFF (ie, delay) separately.
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The Robman · Posted: Tue Mar 06, 2012 10:00 pm Post subject:

eferz · Posted: Tue Mar 06, 2012 10:24 pm Post subject:

vickyg2003 · Posted: Tue Mar 06, 2012 11:31 pm Post subject:

vickyg2003 · Posted: Wed Mar 07, 2012 12:40 am Post subject:

BTW I updated my rough draft of the Humax because I had the zero, one two and three values mixed up. But someone had already downloaded it.
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eferz · Posted: Wed Mar 07, 2012 1:57 am Post subject:

3FG · Expert Joined: 19 May 2009 Posts: 3367

I decoded this by first noticing that the number of burst pairs wasn't constant among the various functions, but the total time was constant. That's a strong indicator that it is some kind phase shift keying. We see it all the time with bi-phase signals like RC5. Also, if it is phase shift keying, the time per digit has to be constant. For example, RC5 uses 2 units of time per digit, and the receiver depends on that fact in order to know when the next relevant transition will occur.

Next, with eferz' learns, which have very little jitter, we can see that the minimum time between transitions is 6 periods of the modulation, and the longest is 37 periods between transitions. So I think of that as the shortest time is 1 unit and the longest is 6 units . There were lots of instances of repeated burst pairs of 2, -2. So I chose to believe that each digit lasts for 4 units. 6 units of off (the longest such time observed) could realistically then be made up of <1,-3> followed by <-3,1>. (In principle it could also result from some combination of -2, -4 or -1, -5, but neither of those will work with a 4 unit digit time.)

So a single digit could take on 6 values-- <-3,1> <-2,2> <-1,3> <1,-3> <2,-2> <3,-1>. However, <-1,3> and <3,-1> aren't seen here, probably because base 6 arithmetic is not so easy to work with. When the designers picked 4 digit values, of course they discarded the two with long on times.

So really, once we've decided to try phase shift keying as a candidate decoding, the rest follows pretty easily. The only other thing to worry about is if the protocol begins with an on burst that is used as a start mark only, then the start of each digit would be shifted, but that wasn't the case here. It is still possible that the protocol begins with a start digit or lead in.

BTW, this is not a "bi-phase" protocol. It is a quad phase protocol, because there are 4 values (phases) within a digit.

vickyg2003 · Posted: Wed Mar 07, 2012 4:38 am Post subject:

bnordman · Joined: 04 Mar 2012 Posts: 17 Location: OH / USA

You guys are just scary when it gets to this. Amazing.

I am just the outside who is hoping that we can get a useful remote out of this so I can use the Slingbox that I bought...

Thanks for all the work and input on this. It is greatly appreciated!
Bjoern

vickyg2003 · Posted: Thu Mar 08, 2012 3:21 pm Post subject:

Here is a KM file that seems to shoot the signal. There still may need to have some minor tweaking of the time-offs, as this signal looks to be a tad bit shorter than the ict-learns I was working from.

http://www.hifi-remote.com/forums/dload.php?action=file&file_id=10796

I've also updated the protocol builder file above.

Question for Rob, was there a way to use your obc's in KM? I just multiplied them by 2 and added 1 if the real obc was even, but was there a way where I could have kept the OBC and had a checksum bit separately?