Have this problem:

I can manually easily decode this using Manchester:

enter image description here

It will be

01010100001 etc

However how should I decode this:

enter image description here

It should be a start sequence code. However on the first screenshot, all nicely aligns, and on the second it looks misaligned in this sequence part, later it aligns (I hope you see this). How to decode this?


Update 1:

Added bigger screenshot of the signal (amplitude plot)

Why the bar pointed by the arrow is not the same size as others? This causes the misalignment.

Where is here clock where is data?

How to decode 8 bits of this signal, starting from preamble 0101 ...?


enter image description here

Update 2:

Here is the continuation of the signal, I tried to decode it (see Red Text on the diagram)

Thick lines I think ís clock (which repeats one is up, than is down etc, on each cycle)

Please correct me if I am wrong.

enter image description here

  • 2
    \$\begingroup\$ What the heck are we looking at here? But in any case, the first step in decoding is clock recovery -- aligning your receiver clock with the incoming edges. How are you doing that? \$\endgroup\$ – Dave Tweed Jan 26 '19 at 14:48
  • \$\begingroup\$ Thanks for your comment. It is a capture using osmocom sdr-rtl from 2 keyfobs. I am a beginner. Not sure what you mean, but for the first example I dont think I had to do clock recovery (maybe I did it by accident), the whole signal align nicely and I can decode it. The second one as I wrote in the beginning (start packet) looks weird. Anyhow, what steps should I take to decode it manually (using pen and paper) from capture? \$\endgroup\$ – dev Jan 26 '19 at 15:01
  • 2
    \$\begingroup\$ Those of us who don't use osmocom, but nevertheless have experience with Manchester codes, cannot interpret the fuzzy images you included. I expect to see a clock waveform and a data waveform but I just see blue smudges. Can you zoom in on a small portion of the waveforms and make them more readable? \$\endgroup\$ – Elliot Alderson Jan 26 '19 at 16:01
  • \$\begingroup\$ Thanks everybody for help. The screenshot is from Inspectrum. I added amplitude plot (green). I think there should be clock and data as you say. Maybe you can see it. I need I think only 8 bits from highlighted area. Will post better imaga as soon as possible. \$\endgroup\$ – dev Jan 26 '19 at 16:42
  • \$\begingroup\$ @ElliotAlderson Added bigger screenshot. See Update 1. Does this help? \$\endgroup\$ – dev Jan 26 '19 at 19:16

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