IR Remote - home page

[last updated: 2025-01-16]
IR Remote Control Codes
TV antenna - rotating
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This page is in process ...

• Goal:
  The intention is to build a "universal" IR remote that can control all my devices that use IR control.
  This adventure has started with Adafruit's tutorial, plus other resources of course, all listed in refs/links below.
  Major steps:
  • build a circuit with an LED receiver chip
  • write program to capture raw IR signal data.
  • write program to decode raw data into usable format.
  • test my existing remotes, and create a "mapping" between decoded signal and button that was pressed.
  • build a circuit with an IR LED that will send out pulses, programmed per the mapping from existing remotes.
  • put all circuits and sensors into package with a touch screen GUI interface.

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  • Initial direction has been to implement this in Arduino,
    at least for study and investigation of the process and software strategy.
  • However it's likely the Arduino is not powerful enough to do the GUI that I want in the end.
    though it may be possible to use the ESP32, and the WT32-SC01 may work.
  • Or it may be necessary to change horses completely and go to a raspberry pi.
    though biggest problem so far is that I want this thing to run on batteries,
    and the rPi does not have a sleep/standby mode,
    though the "Sleepy Pi" add-on board ($45) could be a workaround.

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• Broad Overview:
  • IR remote controls ("clickers") have an IR-emitting LED. They emit light (hence "IR senders"), but IR wavelengths are invisible to our eyes.
    The light emitted by the IR sender is encoded as a pattern of pulses to identify the button that was pressed on the remote.
    The encoding algorithm is complicated.
  • The encoded IR light pulses get received by an IR Receiver. The receiver may be located on your TV, or DVD player, or on a light bulb,
    or on any number of other devices that have receiver circuitry.
  • The IR receiver "decodes" the IR pulses and determines which button was pressed,
    then it does whatever it's programmed to do, eg. turn up the volume, start playing a DVD, change a light bulb color,
    or, if the receiver is just on a computer or micro-controller (eg. Arduino), it may just display the decoded data for manual analysis.

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• Encoding Algorithm:
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• IR Receiver:
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• The first such "meaning" to be extracted is the start code, which not only delineates the start of the data,
  but also correlates to the manufacturer/protocol according to the specific start code that is used.
• Next is the actual data. As mentioned above, the length of the bursts in a data stream will vary in length, but will cluster around two values
  (sometimes three, but at this moment I don't have an explanation for that. Stay tuned...)

  One of those values will be decoded as a binary-1, and the other as a binary-0.

  Note that the lengths of the spaces are almost always relatively constant, and in fact are ignored,
  since the data that is needed is encoded in the lengths of the pulse bursts, and is not affected by the length of the spaces.

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• Another way to decode the signals, instead of using Adafruit's brute-force method, is to use a contributed library that has done all the heavy lifting for you,
  and will just spit out a single code to identify a given button press.
  At this time I have only investigated two such libraries:
  • The IRremote library:
    3.6.2 available: https://github.com/Arduino-IRremote/Arduino-IRremote
    3.6.1 Added with Library Manager
    After some editing for new library version, it worked, (IR_LEDsensorDecode.ino)
    printing out two, 8-hex-char numbers for each keypress on the remote.
        See: IR Remote Control Codes

  • The IRLib2 library:
    • This is shown in "...using-an-infrared-library.pdf" (link below):
    • Installation of the library must follow the steps in the pdf. The library-master.zip that you download from github
      actually contains 5 separate libraries,
      so trying to install it using the IDE - sketch - include library - add zip library will fail for "ERROR 13 ... library not valid"

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  moved to my custom folder:
      .../tech/Arduino/programsLibrariesUser/librariesOrigMasters
  • Back to pdf to follow its more involved procedure:
    • In my librariesOrigMasters folder, double-click on IRLib.zip, extract, extract
      IRLib2-master folder was created, with the extracted files in it.
      moved the IRLib.zip into it for archive
    • Indeed the un-zipping created the 5 individual library folders that the pdf mentioned:
      IRLib2, IRLibFreq, IRLibProtocols, IRLibRecv, and IRLibRecvPCI
    • Copied all 5 folders into my sketchbook library folder: .../tech/Arduino/programsLibrariesUser/libraries
      restarted IDE
      Successful
  • Testing IRLib2 Example programs:
    • The dump.ino example program reads IR pulse streams sent from a remote,
      and decodes it. It gives you several pieces of information:
      First, it tells you the protocol being used:
      These data are for pressing the LEFT button on Vizio remote
          eg. "Decoded NEC(1): ... "
      Next it gives the hex value of the decoded command:
          eg. " ... Value: 20DFE21D ... "
          The pdf says this data value "uniquely encodes" the button press.
      Then it gives some other stuff, and finally the actual data:
      eg. "0:m554 s606
      1:m522 s578
      2:m550 s1702
      3:m542 s586
      4:m550 s586
      5:m542 s582
      6:m546 s610 ... "
      and continuing for 32 chunks.

      At this point in time I have no idea how to interpret these data...
      however I see this: repeated presses of a given key will always show the same decoded hex command,
      though the raw timing data (the m... and s...) vary slightly.

      The hex value of the VIZIO DOWN-VOL command: 20DFC03F

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