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    Convert Pulse Train w/ both positive and negative pulse

    Hi,

    I am looking to Convert a Pulse Train w/ both positive and negative pulses into a suitable form to be used by an FPGA board. I have to also keep track whether the pulse was positive or negative.

    Any help appreciated!


    Thanks

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  2. #2
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    Re: Convert Pulse Train w/ both positive and negative pulse

    Do you mean a debouncing circuit?



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    Re: Convert Pulse Train w/ both positive and negative pulse

    Quote Originally Posted by kieshpup View Post
    Hi,

    I am looking to Convert a Pulse Train w/ both positive and negative pulses into a suitable form to be used by an FPGA board. I have to also keep track whether the pulse was positive or negative.

    Any help appreciated!


    Thanks
    If you could provide a diagram of what you are trying to capture, we might be able to better assist you. Just right of the bat though, it seems like you will need a state machine to process the incoming data.

    Also, what exactly do you mean by negative pulses. Applying an actual "negative" voltage to the FPGA pins will damage the device.

    Regards,
    Willis



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  4. #4
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    Re: Convert Pulse Train w/ both positive and negative pulse

    The easiest way is to level-shift the pulse train up into the positive region.

    Attenuate as necessary so it ranges from zero to 5V (or your supply V).

    Incoming positive pulses will become higher than V/2.
    Incoming negative pulses will become less than V/2.
    Idle periods will be at about V/2.

    You must set thresholds for these ranges, so the FPGA can discern what to call an incoming signal.



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