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SHIFTIN and SHIFTOUT over some length of wire? — Parallax Forums

SHIFTIN and SHIFTOUT over some length of wire?

GenesisGenesis Posts: 42
edited 2005-12-15 06:03 in BASIC Stamp
Anyone done it?

BS2pe here, so the data rate is reasonable (~16kbps).

I'm considering trying to run TTL data over a ~3' length of cable to an ADC that is not physically colocated with the BS2pe this way.

Wondering if anyone from Parallax can think of a reason why it wouldn't work (properly bypassed for noise, etc of course) - I can think of a few reasons it might be trouble (e.g. cable capacitance) but it could be a potential solution to a design problem I'm wrestling with.....

Comments

  • Bruce BatesBruce Bates Posts: 3,045
    edited 2005-12-13 06:59
    Genesis -

    I don't forsee any problems, but if you experience any, shout back. There are "booster" chips available. I'll have to dig out the chip number if you need them.

    Regards,

    Bruce Bates
  • allanlane5allanlane5 Posts: 3,815
    edited 2005-12-13 13:56
    Three feet shouldn't be a problem, as long as you run a good ground wire along with your clock and data wires.
  • GenesisGenesis Posts: 42
    edited 2005-12-13 14:02
    Cool - will give it a shot and see what happens [noparse]:)[/noparse]
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2005-12-13 14:44
    Generally, the slower you go, the farther your information will travel. If you have trouble, reduce your clocking speed to clear it up.

    Traditional RS-232 had a sychonous mode, so I suspect you can use the conventional RS-232 drivers and receivers to set up a much longer distance than 3 feet.

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  • GenesisGenesis Posts: 42
    edited 2005-12-13 16:35
    I can't reduce the clocking speed - that's the problem.

    SHIFTIN and SHIFTOUT are intended to clock data from bit-serial devices on the BS modules, and their speed of operation is more-or-less a function of the chipset itself. It doesn't have a "baud rate" per-se.

    The idea here is to remote the ADC from the stamp, placing it and signal conditioning (op-amps) close to the physical sensors (desireable for various reasons) while having the stamp in a slightly different location.
  • GenesisGenesis Posts: 42
    edited 2005-12-15 06:03
    It works quite well over a 5' length of ordinary Cat 5 UTP with no attention paid to paring or grounds whatsoever.

    Even with one of those "Ion storm" plasma balls running right next to it......

    I'm impressed.... I DID bypass both ends like stink, but still, I expected trouble. Looks like its going to work.
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