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 874 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?
jsimon669
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Re: Problem with Manchester encoded RC5

Post by jsimon669 »

Any update on this? It seems I am having the exact same problem where the first edge is missed and throws the entire decoding off.
gwolf
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Re: Problem with Manchester encoded RC5

Post by gwolf »

Problem never to be solved?
Martyn
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Re: Problem with Manchester encoded RC5

Post by Martyn »

This is actively being worked on by the team as part of a new Manchester based decoder we are introducing, so should be resolved in an upcoming release of the Early Access software
Martyn
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Re: Problem with Manchester encoded RC5

Post by Martyn »

In the latest release of PicoScope 7 Early Access 7.1.17 we have added a new option on the Manchester Decoder setup panel. This allows you to specify the number of edges to ignore at the start of a packet. For normal Manchester this is set to 1, but for signals such as this RC5 set this to 0.

The download is available from within the software, or from the downloads tab at the top of the page.
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Maksim
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Re: Problem with Manchester encoded RC5

Post by Maksim »

Dear developers!

After updating to version 7.1.21, I lost the ability to work with the proprietary Manchester-based protocol. Your decoder was not a perfect tool. There is no option to describe star/stop conditions, which are beyond the scope of the coding of this protocol. But having learned to adjust it manually, I could get the information I needed.

Now I can't do it! Both decoder options perceive the star condition as the end of the frame.
This is what decoding looked like before changes in the decoder (I was able to get it by rolling back to version 6)
WhatsApp Image 2024-05-06 at 08.50.54.jpeg
WhatsApp Image 2024-05-06 at 08.50.08.jpeg
This is what it looks like now
1.jpeg
I am also sending you a fragment of a captured stream that I have to work with.
To Pico.zip
(1.42 MiB) Downloaded 328 times
Please return the ability to use the old version of the decoder

Or exceed all my expectations and add the ability to determine star/stop conditions :)
Martyn
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Re: Problem with Manchester encoded RC5

Post by Martyn »

We have found an issue with loading Manchester Decoders into the software where they switch to using the DIfferential Manchester Decoder in error. There is a fix for this currently in test and once available I will check your files against this.

Can you please reach out to us at support@picotech.com with your requirements for a star/stop configuration and we can take a look to see if it would be possible to impment this.
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Maksim
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Re: Problem with Manchester encoded RC5

Post by Maksim »

First of all, I want to thank you for such a quick answer. The mistakes in the releases are inevitable, but the reaction speed pleasantly surprised me! Keep it up!

In anticipation of the correct release

Regarding the of the start/stop condition: I will try to describe in more detail what they are in my case. And if you can solve this problem, of course, save me time to diagnose a problems.
But due to the features of my work, I must solve various problems with various protocols. I understand that you cannot fulfill all my requests. Maybe you will think about the level at which the user will be able to prescribe his logic of interpretation of the received data based on the base protocols (UART, SPI, I2C and ect.)
bennog
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Re: Problem with Manchester encoded RC5

Post by bennog »

Depending on your programming skills, you can always use the SDK and write your own decoder.

I have done this for situations where picoscope could not trigger on the rare problems we had.
The only problem with this is that displaying the captured data is than aso your problem.

Benno
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