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keypad scanner

Discussion in 'Electronic Design' started by [email protected], Jun 3, 2005.

  1. Guest

    Hi all,

    I am implementing a 6x6 matrix keypad scanner in CPLD.
    My requirment is i should detect multiple key presses also.
    What i am planning to do is , i will scan the rows (6 of them
    sequentially) , when all the 6 rows are scanned i will send the 36 bit
    output(each bit corresponds to each individual key .'0' indicates
    pressed)to the controller.The scan rate for each row is approximately
    32 msec , so every 32x6=192 msec i will be sending the 36 bit code to
    controller(HCS12).

    I want your comments on this implementation in CPLD.

    Regards,
    Praveen
     
  2. On 2 Jun 2005 20:54:35 -0700, the renowned
    That's way too slow a scan rate.


    Best regards,
    Spehro Pefhany
     
  3. Rich Grise

    Rich Grise Guest

    Why the specification for a "Complex programmable logic device"? Is
    a microcontroller out of the question? That is a programmable logic
    device, and typically fairly complex, so it _would_ fit your spec,
    and implementing something like your app in firmware would be a
    snap - doing it with a big registered gate array would be a freaking
    nightmare, IM!HO.

    Or, just scan it with the contoller itself. What's an "HCS12?"

    You can get microcontrollers, like the PIC, that have 16 I/O lines,
    which would give you 12 for your scanner, and 4 more for data with
    handshaking. I'm not a PIChead, so have no idea which of the vast
    family you'd want to choose, but someone here will surely help out
    in that respect.

    Some also recommend AVRs or Basic Stamps - any of these could do
    the job.

    Good Luck!
    Rich
     
  4. Probably a homework question from an Indian university.
    Successor to the Motorola HC11, from Freescale. They've changed the
    numbering system a bit... now they have numbers like MC9S12..
    Scanning a keyboard would use negligible processing power of any of
    that series.

    Best regards,
    Spehro Pefhany
     
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