Did you know that... Dallas 1-Wire search trick/work around


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  1. #1
    Join Date
    Oct 2009
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    Default Did you know that... Dallas 1-Wire search trick/work around

    Hey group,

    Just thought I'd relate my findings with respect to the 1-wire protocol.

    I have a project that uses two 1-wire devices. A DS18b20 temperature sensor and a DS2417 Real Time Clock. I needed both devices to share the same PIC pin.

    So I spent much time working on the 1-wire discovery code that I found here... http://www.picbasic.co.uk/forum/showthread.php?t=3671
    which actually works quite well (thanks jimbab!!)

    Then after studying the different command sets for each device I realized that there was no overlap between them.

    So I have tested and verified that I can still use the $CC (skip ROM) command and talk to each sensor as though it was the only one on the line because the Function command sets for each device don't overlap..

    I have been able to read and write to both sensors on the same line, no problems (so far).

    I was planning on using the search routine so that I could swap out 1-wire devices and have the code learn the address of the new device without my intervention. But now I don't need to.

    Now keep in mind this only applies if the two (or more??) devices don't share any function commands.

    I had even called Dallas/Maxim to inquire if there was a way to just specify the family code to access each device without having to include the full 64 bit ROM code. The engineer told me I would have to include the full address.

    This simplifies my code quite a bit. Sweet!
    Last edited by Heckler; - 16th February 2015 at 17:41.
    Dwight
    These PIC's are like intricate puzzles just waiting for one to discover their secrets and MASTER their capabilities.

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