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Easier: Interfacing 5v to the Prop. — Parallax Forums

Easier: Interfacing 5v to the Prop.

Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
edited 2008-06-30 17:37 in Propeller 1
Picked up a couple of these from Sparkfun.
Looks like a really easy way to handle the 5v--3v interfacing issue.

Logic Level Converter
www.sparkfun.com/commerce/product_info.php?products_id=8745#

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Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2008-06-30 16:07
    The transistor circuit that board uses is the one recommended by NXP (Philips) for connecting two I2C busses of different voltages. It's bi-directional, not unidirectional, as the SparkFun website implies. NXP has a patent on that circuit, too. I wonder if SparkFun doesn't realize it or if NXP just isn't enforcing their patent.

    -Phil

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  • RaymanRayman Posts: 14,817
    edited 2008-06-30 16:10
    Nice and simple...

    PS:· I think a patent on a simple circuit like that is rediculous!· I doubt it would hold up in court anyway...
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2008-06-30 16:31
    Things are always simple when you see them done but someone has to come up with the idea in the first place. It would hold up perfectly well unless it can be shown to have been done already and in some dark corner of the world that is quite possible. Anyhoo enough of patents.

    Graham
  • parskoparsko Posts: 501
    edited 2008-06-30 16:32
    In theory, one could use a transistor instead of the Mosfet, and have no hit in performance, right?

    @Graham,
    I think NXP would have to sell an actual product for it to hold up. It seems too obvious and idea to try to defend.
  • LeonLeon Posts: 7,620
    edited 2008-06-30 16:40
    A patent doesn't have to be incorporated in an actual product to be valid and enforceable.

    Leon

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  • Graham StablerGraham Stabler Posts: 2,510
    edited 2008-06-30 16:42
    So obvious they had to invent it and I2C isn't that old is it?

    Leon is correct although there is not much point defending it for the sake of it.

    Graham
  • parskoparsko Posts: 501
    edited 2008-06-30 16:50
    @Leon
    Totally! But, at $1.95 per board? And I doubt Sparkfun will sell millions. AND, I don't see Phillips as that big a bean counter. It does them more good to ignore than to litigate, right?
    Sorry, no more about patents.

    But, can one simply replace the mosfet with a transistor? Just clarifying, cause at some point (soon) all my sensors will go 5V.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2008-06-30 16:53
    I'm kinda sorry I brought up the patent thing, except that its existence has been instrumental in some of my recent design decisions. Yes, there are equivalent bipolar transistor circuits. The bidirectional ones I've seen use two transistors instead of one.

    -Phil

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    'Still some PropSTICK Kit bare PCBs left!
  • LeonLeon Posts: 7,620
    edited 2008-06-30 16:55
    Philips holds the patents on I2C, of course. They seem to enforce those.

    Most circuits I've seen for converting between buses with different logic levels use MOSFETs.

    Leon

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    Post Edited (Leon) : 6/30/2008 5:01:07 PM GMT
  • hippyhippy Posts: 1,981
    edited 2008-06-30 17:37
    www.nxp.com/products/interface_control/i2c/licensing

    "I2C licenses for standard mode under the remaining patents in the program will be free of any royalties, for any use of the patents after October 1, 2006, without any prejudice to any claims for past use whatsoever".

    Previously that page used to say ...

    "I²C Licensing information - I2C licenses under the remaining patents in the program will be free of any royalties, for any use of the patents after October 1, 2006, without any prejudice to any claims for past use whatsoever".

    Not sure Phillips can retrospectively tighten up or restrict such a license, and I have no idea whether it applies to this buffer or not but I wouldn't expect a knock on the door from their lawyers.
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