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Pilot
Joined: 06 Jul 2004
Posts: 9
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| Multiplexing LCD & Keypad |
 Posted: Fri Sep 03, 2004 3:38 am |
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Hi,
I couldnt find :( Coluld you pls shortly explain the logic, give example code & shematic? Thanks (LCD is driven in 4 bit data mode) |
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Trampas
Joined: 04 Sep 2004
Posts: 89
Location: NC
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| Posted: Sun Sep 05, 2004 5:55 pm |
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Pilot,
I guess we need some more detail, or this was part of another thread?
Trampas |
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Pilot
Joined: 06 Jul 2004
Posts: 9
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| Posted: Mon Sep 06, 2004 12:17 am |
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| Trampas wrote: | Pilot,
I guess we need some more detail, or this was part of another thread?
Trampas |
I mean how can LCD and Keyboard share same pins?
My project has 3 buttons & 7 pins connected to LCD.
I wonder, can I use 3 or 4 lines of the LCD to read the buttons?  |
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Guest
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| Posted: Mon Sep 06, 2004 12:59 am |
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Replace D2 ... D6 with 470 ~ 1k ohm should work
That's how I made it work.
Best wishes |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Mon Sep 06, 2004 6:42 am |
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| You should not need to replace the diodes. To read the keypad, set each "row" to 0. Start and the first row and set it high (1). Now look at each column. Any column that is high will mean that the key at that row/column is pressed. Now set the first row back low and move to the next row and repeat the process until all the rows are done. So long as the LCD is now enabled this should not affect the operation of the LCD. |
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