How can I use RA4 in PIC18F452

Discussion in 'Embedded Systems and Microcontrollers' started by raychar, May 28, 2012.

  1. raychar

    Thread Starter Member

    Nov 8, 2011
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    I made a board which uses PIC18F452 to control the working of18 pieces 7 segment LEDs . By multiplexing method, almost all pins in controller are used. All LEDs are functioned correctly except the one that using RA4 pins.

    That pin was already configurared as output as were done on others, however, there is no voltage output on this when I measure it.

    I tried to put another IC, same phenomenon persists.

    Could anybody help to advise what's problme or what mistakes I made?

    Thanks
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Put a pull-up resistor on RA4.
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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  4. raychar

    Thread Starter Member

    Nov 8, 2011
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    Thanks for the reconfiming this method, I now suceed. May be my program was not matured before when I used this method previously and then made unsucess and misleading to me.

    Many thanks..
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,429
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    This has nothing to do with your program. This is the way RA4 is built.
    AS shown in the Data Sheet, RA4 is an open-drain output.

    [​IMG]
     
  6. raychar

    Thread Starter Member

    Nov 8, 2011
    82
    0
    Yes, understand, thanks!
     
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