How to decode RCMM philips protocol

Discussion in 'Embedded Systems and Microcontrollers' started by asheesh, Dec 17, 2013.

  1. asheesh

    Thread Starter New Member

    Dec 17, 2013
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    hello everyone, I am trying to decode RCMM(philips protocol) using VISHAY TSOP31536 IR Receiver with STM32F207 microcontroller kit. There is sufficient data for RC5 protocol but not even a single site is explaining about RCMM. Even the details of RCMM specified(frame/message details) in documents is quite different from what I extracted from the CRO in lab. Please let me know from where can I find reliable RCMM documentation or any useful help?
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The web page you linked to is excellent and gives all the information you need to get started.

    One good suggestion is to build an "IR sniffer" by attaching a 3pin IR sensor chip to a storage scope or logic analyser.

    Then you can record and display the actual IR message. That will help you debug the pulse timings and code format.
     
  3. asheesh

    Thread Starter New Member

    Dec 17, 2013
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    @THE_RB Sir, with due respect, the web page of which you are talking about doesn't match with the actual parameters of RCMM, which I extracted on CRO using IR receiver. Each pulse is coming out as a 32 bit data(0x2600A700 or 0x 26002706) which nowhere matches with this web page data. That's why I put this ques & that web page too
     
  4. hexreader

    Active Member

    Apr 16, 2011
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    Why are you so sure that it is RCMM protocol?

    Looks more like MCE protocol to me, judging from the sparse information given.
     
  5. THE_RB

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    Can you post a screenshot of the waveform you are getting?

    And the details of what brand and type the remote control is would help. :)
     
  6. asheesh

    Thread Starter New Member

    Dec 17, 2013
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    @hexreader, sir because the remote which I am using, uses RCMM protocol. As the project in which I am currently working is a part of some high level project & the concerned information related to this is quite true.
     
  7. hexreader

    Active Member

    Apr 16, 2011
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    I agree with RB, we need to see the waveform before we can help.

    Preferably several waveforms - for different remote buttons.
     
  8. asheesh

    Thread Starter New Member

    Dec 17, 2013
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    @hexreader-@RB,, please find the waveform-snapshots from here of remote keys 1 to 9. In my opinion, each signal is containing 32 bit of data(excluding Header); as in RCMM protocol, each Off-Time(or Space value) produces one of the 4 possible bit-patterns(00, 01, 10 & 11) based on that Off-Time value since On-Time(or Mark value) remains the same in all cases. You can check out this link for reference although the On-Time & Off-Time value of my waveform don't match with this link.. Waiting for a +v response
     
  9. hexreader

    Active Member

    Apr 16, 2011
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    I am no expert, but it looks to me like a proprietry protocol which is a variant of RCMM. My guess is that you will not find any definitive information, as the manufacturer will want to keep their intellectual property secret.
    It looks easy to decode though - and the timing does appear to match that in "SB projects" site (to my eye).
    I would say that the waveforms show -
    (header) --- (extended mode 9) 00 10 01 --- 10 00 00 00 10 10 01 11 00 00 xx xx
    where xxxx = button number 0001 to 1001 (button 1 to 9)

    Be aware that the received timing will be distorted a little from the transmitted signal. Mark times will be stretched a little, while space times will shorten. As the distance between transmitter and receiver varies, the timings will change a little.

    It is clear that you already understand that your receiver gives an inverted signal, which is perfectly normal.
     
    Last edited: Jan 3, 2014
  10. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    It looks easy enough.

    You can see the 4 different bit timings, so zooming in a bit on the 'scope will give you pretty accurate timing period measurements. Then just set your period divider values in software to be halfway between the measured periods.

    Then just get your STM micro to decode and display each code as hex on its LCD.

    After that you can press each button on the remote and see the hex result on the LCD, so you can write down all the remote codes and incorporate in software later.
     
  11. asheesh

    Thread Starter New Member

    Dec 17, 2013
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    @hexreader-@RB,, Thank you so much for your valuable answer. I'll look into it.
     
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