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  1. #1
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    i2c length

    Hello,
    I am designing a device that uses a PIC to flash goggle-mounted RGB LED's with adjustable rate and brightness. I was considering using I2C or SPI to drive the LED's from an I/O expander also mounted on the goggles. Is this a viable idea, or is there a maximum wire length for reliable operation? Thanks in advance for your help.

    •   Alt16th November 2006, 08:55

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    i2c cable length

    hai
    i checked a lot for this
    i found from the philips this.
    the maximum cable capacitance is limited to 500pf
    a cat5 cable has the capacitance of 17pf/feet
    anyway i think it's possible to use I2C in small distance communication.

    regards


    sun


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    •   Alt16th November 2006, 14:18

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    i2c distance

    The length can be increased significantly by running at a lower clock frequency. One particular application - clocked at about 500Hz - had a bus length of about 100m (300ft).


    http://www.esacademy.com/faq/i2c/q_and_a/faq/i2cqa1.htm



    •   Alt2nd December 2006, 11:38

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    i2c max length

    There's a PLC maker in my country that states one of its equipment can connect to some sensors up to 1km far away using its onboard i2c channel.

    I have no idea how this can be achieved. Low frequency???

    Ric



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    i2c maximum length

    Dependes upon noise margin of the rxd circuit .



  6. #6
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    i2c wire length

    I2c is data level

    you simply add buffers to rework the signal levels

    every so often

    or you use an amplifier and a comparitior to rework it back to real data
    when at distances ....

    i2c error checks
    so this isnt a problem

    its there or its not like digital TV

    appart from this

    copper wire is around .12R per meter for a single telephone style cable core

    so simply work it out using resistivity of the cable and its lenght
    against the driving voltage
    so you can calculate the output voltage
    against the current you need to switch your distant device

    if its less than you need simply use a cmos gate to buffer it or cmos ttl

    they are very sensative high impedance inputs
    and need micro amps to switch them
    most often pico amps


    i would use an rf pic if you have little distance to go

    or if its a vast distance use the net and a ip stack controller


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  7. #7
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    i2c maximum distance

    Hi

    It depends on your speed , supply , pull up resistors , bus & load capacitance.

    just serch the net for USB specifications
    it's a fill from philips with all the data you need

    Salam
    Hossam Alzomor
    www.i-g.org



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