Problem with Manchester encoded RC5

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gwolf
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Problem with Manchester encoded RC5

Post by gwolf »

Manchester serial decoding does not work for the output signal from my TSOP33436 IR receiver (RC5 protocol). Instead of positioning the first bit at the first transition (which is from +5V to 0) it does so at the second transition. The results are wrong packet length (13 bit instread of 14) and wrong data.

PicoScope® 6 - PC Oscilloscope software version: 6.14.61.6219
Model: PicoScope 2204A

Martyn
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Re: Problem with Manchester encoded RC5

Post by Martyn »

Can you supply a psdata file so that we can see the issue.
Martyn
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gwolf
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Re: Problem with Manchester encoded RC5

Post by gwolf »

RC5.psdata
(16.88 KiB) Downloaded 15 times
Attachments
Unbenannt.JPG

Martyn
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Re: Problem with Manchester encoded RC5

Post by Martyn »

I have raised this for investigation by the team, it looks as if we may not be detecting the first edge as the start bit so end up being 1/2 a bit out throughout.
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bennog
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Re: Problem with Manchester encoded RC5

Post by bennog »

I think the start flank is missing in this signal.

Every example I have found has a halfway signal when idle and has a edge half the amplitude as a start of package timing trigger. Also if you count the full bits then you see the first bit should have a staring edge before the first edge.
Something I have added in red in the below scope image.
2022-12-19_20-21-19.png
I have also exported to sigrok and gave the same inconsistend timing result.
2022-12-19_21-44-54.png

gwolf
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Re: Problem with Manchester encoded RC5

Post by gwolf »

Perhaps our problem is that Manchester encoded signals look different on a data line (no DC component) than on the output of an IR receiver (idle = 5V).

gwolf
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Re: Problem with Manchester encoded RC5

Post by gwolf »

I suppose that we dealing here with logic systems, where a halfway level does not exist.
Any results from your investigation?

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