7 segment & LCD ressources!

Discussion in 'Embedded Systems and Microcontrollers' started by Eric007, Aug 30, 2011.

  1. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    Hi All!

    Can anybody give my links or pdf file or whatever on 7 segment & LCD?

    I actually need documentations on how to multiplex 2 or more 7 segment (hardware configuration first, then software)...

    To not create another thread, please also send links about LCDs

    Thx all
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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  3. nickelflipper

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    Jun 2, 2010
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  4. srikanthsamaga

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  5. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    Thx guyz!!!
     
  6. MMcLaren

    Well-Known Member

    Feb 14, 2010
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    Sorry I missed this thread Eric,

    If it helps, I posted an LCD example in this thread; 16F690 interfacing with LCD 16x2

    [​IMG]

    You can also use a shift-register or serial-to-parallel latch IC to build an LCD "backpack" in order to free up some I/O pins. One example below uses four I/O pins for (A) LCD display, (B) four general purpose outputs, and (C) four push button switch inputs.

    Regards, Mike
     
    Last edited: Sep 3, 2011
  7. MMcLaren

    Well-Known Member

    Feb 14, 2010
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    Hi Eric,

    Asking for 7-segment LED examples is like opening up a flood gate (lol). There are hundreds of different ways to interface to a 7-segment display. Here are a few (of many) different ways;

    (1) use discrete daisy-chained serial-to-parallel ICs like the 74HC595 (25 ma sink/source) or TPIC6C595 (90 ma sink) to drive one or more 7-segment displays with a 100% duty cycle. the advantages include not having to "refresh" the display periodically as you would with a multiplexed display, and only three I/O pins would be required. One somewhat exotic method (Roman Black's "shift1" method) only requires one I/O pin. The disadvanges include using more ICs, one for each display, than you might use for a multiplexed display.

    (2) multiplex the displays using "direct" I/O drive from the PIC. This uses a lot of I/O pins. for example, you would use seven pins to drive the A-G segments and three pins to drive the CA or CC transistors for each digit on a three digit display. the duty cycle of the display becomes a concern since you need to increase the "peak" current per LED to maintain "average" current and brightness. with "direct" I/O drive your brightness will be limited by the current capability of the I/O pin ("peak" current available) and the number of digits in the display (duty cycle).

    (3) Charlieplex the displays, another form of "direct" I/O drive, uses slightly fewer I/O pins. for example, eight pins would be needed to drive one to seven digits. the rather exotic Charlieplex wiring is a bit complex and prevents using multi-digit displays that have multiplexed pin outs.

    (4) multiplex the displays using a driver IC. this method allows better "peak" current management and brightness control. it uses fewer I/O pins compared to the "direct" I/O multiplexing methods. like the other multiplexed methods mentioned above, the displays need to be "refreshed" periodically in order for each digit to appear to be continuously lighted. there are hundreds of variations.

    More later. Regards, Mike
     
    Last edited: Sep 3, 2011
  8. Eric007

    Thread Starter Senior Member

    Aug 5, 2011
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    Thx a lot MMcLaren...looks like I still have lots to learn...
    This gon be a very long "PIC" trip...goto have my belt well fastened...

    Eric007
     
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