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Parallel Port EPP Interface

Discussion in 'Electronic Basics' started by Sebastian Meuren, Apr 5, 2004.

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  1. Hello!

    I`m developing an EPP-Interface for a Microcontroller (AVR) and I have a
    problem: Some Bytes are lost (randomly) and I don`t know why this happens.
    Does anybody know why or how this can be fixed?

    Thx for help, Sebastian....
  2. Aaron Hughes

    Aaron Hughes Guest

    You may be experiencing BOUNCING. The parallel port is typically open
    collector and in my experience, very noisy. You may solve this by putting a
    Schmitt trigger (7414) on the parallel
    port outputs (and then have your software correct the bits ie invert them
    before sending)
    Have your microcontroller detect the change on the parallel port, wait about
    3us, and then read the bus again.

    Most parallel ports run at top speed of 5us to 10us.

    Hope this helps.
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