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Topic:
LG TV Different IR Code Set?
This thread has 2 replies. Displaying all posts.
Post 1 made on Thursday March 16, 2017 at 17:59
CBP
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March 2017
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Hi,

I have an LG TV that is probably one of their custom lines (here in the UK - the model is 50LB561V) and I am already controlling it over IR with a custom arduino type circuit. I captured the IR signals using another arduino, noted what they were captured as and then send them back and they all work, no issues here then they do exactly what I want.

It's now come to me that I would like to send some discrete on/off codes to help with my home automation system and I have now seen so much information I'm driving myself crazy. I only appear to be able to find one protocol set for LG on every document I have seen on the internet, same for IR and the same for serial. I can't seem to find mention of any additional or different sets of codes.

I've been trying to send the discrete on/off codes now and I can't make sense of any of the captured codes (which work) and the discrete on/off don't work at all. For example if I capture the power toggle it will show:

20 DF 10 EF

Having looked at the NEC protocol it appears that it is LSB first and the second byte is the inverse of the first. I then work that out to be;

02 FD 01 FE

Which does not equate to power on/off in the documentation, it should be from what I can see;

04 FB 08 F7 (so 40 BF 80 7F)

Which is nothing close to what I am capturing, every command I capture starts 20DF which says to me that is the low/high custom code for this set. The last parts of the code also appear to match up when I take the inverse values. This is not just for the power toggle it is for all the commands - before I resort to sending 255 codes and doing it the hard way (and finding out there probably is no discrete on/off code with my luck) can I ask if there is any other known LG protocols that I may be missing?

Many thanks...
Post 2 made on Thursday March 16, 2017 at 19:29
3FG
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August 2009
1,857
The signals are not "inverse"; instead they are bit reversed in order.  What you're doing is reversing the order of the nibbles:  0D becomes D0.  Instead, write D0 as 1101 0000
Reverse the order one bit at a time:
0000 1011   which is 0B.

For NEC, the bit reversal is done on each byte individually, and the bytes themselves retain the byte order

So 20 DF  when bit reversed changes:
0010 0000    1101 1111    (20 DF)
0000 0100    1111 1011    (04 FB)
OP | Post 3 made on Friday March 17, 2017 at 04:16
CBP
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March 2017
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Excellent thank you for the explanation, that works now on all of the codes - I think I just ended up confusing myself at every turn but now makes sense!


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