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Thread: IR Scope

  1. #1
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    Default IR Scope

    Attached is some code for the 18M2 which allows it to be used as an IR scope to see signals received from an IR remote and deliver some analysis of the IR stream.

    It looks for the start of the IR stream then samples as fast as possible into a buffer, analyses what has been received later. To be useful it needs to run fast and have a large buffer to store the samples. The 18M2 program uses most of its 512 bytes of variable RAM as a buffer.

    This technique should work on other PICAXE chips but not well on those with less RAM or a small scratchpad which cannot store all the data of a full IR transmission.

    All reported times are guesstimated rather than measured so do not put too much faith in those. Those calculations will need to be adjusted for other PICAXE and what the code reports for number of bits received etc will depend on PICAXE.

    This was part of an ongoing project to see if the sample then analyse technique can be used to detect and use non-Sony codes, part of a project to be able to independently control two identical Sky digiboxes in the same room. The answer seems to be yes and I will post more on that as the project progresses.
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  2. #2
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    Hello Hippy.

    Very interesting project. Any news on further development?
    Darb

  3. #3
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    I have a different service provider to Sky who now provides comprehensive PVR capabilities so I no longer need to control two Sky boxes and the project became redundant.

    The plan was to use two Sky remotes ( which conveniently come in blue and white ), one programmed to control both boxes, the other to only control a different model box to the one I have. I was going to disable the IR receiver on one then use the PICAXE to capture the IR from the remote programmed wrongly to create the IR signal for the disabled receiver. That could be done by direct access to the IR receiver signal line or via a Magic Eye style input over RF.

    I did another project generating Sky IR codes so it should have worked, but never got as far as trying it.

  4. #4
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    Understood. Thanks for the reply hippy.

    No point in continuing if a new solution prevents itself. I often set up AV gear as part of my day job. On the odd occasion I run into remote code clashes even when the brands are different. Often the codes will work the unintended device and the individual button doesn't correspond to the function. For example, hit eject on a DVD remote and the unintended TV changes channel. Hence this is why I had some interest in the project. This represents a real nightmare in terms of remote compatibility. Often it means the client has to get rid of one of the units and/our put it in another room in the house.

    To the best my knowledge Panasonic are about the only ones to address this issue with most if not all of their gear (particularly PVRs) having up to 7 remote code variations available to avoid clashes. This means the client can have multiple PVRs without issue. All the PVRs (for example) receive the remote signal but only one acts. The others simply display their own remote code to indicate that they are ignoring the command. Clever stuff and I am not entirely sure how they do it. At a guess they "tag" the signal as I couldn't imagine they would have 7 variations of all their remote codes.

    The other reason for interest in the project is the proof that a remote itself is functioning correctly. From my fairly vast experience with faulty remotes, it is often not enough to simply confirm IR output (using a mobile phone camera to see the IR stream for example). Remotes can fail in such a way that they can appear to be transmitting but that transmission can be garbage. This often happens when the ceramic resonator is faulty (drifts of frequency?) which is reasonably common, or the micro/encoder fails. It is usually the ceramic resonator as they don't like being dropped and people seem to regularly abuse remotes.

    I was thinking that your project might have been able to prove if a transmitting remotes stream was valid and eliminate faults within the corresponding unit itself (I have encountered a number of IR receivers that have failed giving the appearance that the remote is (incorrectly) at fault).

    Anyway, that was the reasons for my keen interest.

    Thanks hippy.
    Darb

  5. #5
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    Not sure if I posted this before or elsewhere but it is the code which builds on the IR Scope capture and allows Sky and/or Sony IR codes (7, 12, 16 and 20-bit ) to be received, detected, decoded and the key press and other information to be reported.
    Attached Files Attached Files

  6. #6
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    Thanks hippy. Impressive stuff. I will study the code. I know I will learn a great deal just by looking through your code. I will have a go at using this capture system and see what it can do.

    Thanks again!
    Darb

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