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06/30/06 13:09
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 		 #119427 - Diodes to prevent ghosting
Responding to: ???'s previous message
Jan said:
The general idea of matrix scanning is, that you put 0 on only one of the columns (and 1 on the remaining), and watch, which row goes down to 0 (assuming that there are some pullups which keep the remaining columns in 1).

Yes, and sometimes additional diodes are needed to prevent "ghosting":

http://www.dribin.org/dave/keyboard/one_html/

Kai

List of 36 messages in thread
TopicAuthorDate
4x3 keypad interfacing with At89c51            01/01/70 00:00      
   5 errors            01/01/70 00:00      
      Nice attitude!            01/01/70 00:00      
         If the approach is that anyone can get h            01/01/70 00:00      
            Do we know him?            01/01/70 00:00      
               Switch Depressed?            01/01/70 00:00      
                  continous and continous            01/01/70 00:00      
                     Thanks Erik!            01/01/70 00:00      
                  Taking samples            01/01/70 00:00      
                     debounce scheme.            01/01/70 00:00      
                        How to debounce without jumps and branch            01/01/70 00:00      
                           Thank you Kai...            01/01/70 00:00      
                           Having gone through your detailed descri            01/01/70 00:00      
                              Yes, I think so            01/01/70 00:00      
                                 Could you assist me to know that            01/01/70 00:00      
                                    Vertically incrementing            01/01/70 00:00      
                                       Thanks            01/01/70 00:00      
               Homework it is            01/01/70 00:00      
                  "Guilty"...            01/01/70 00:00      
   Post your code            01/01/70 00:00      
      2            01/01/70 00:00      
         There have been several threads            01/01/70 00:00      
         How to post code            01/01/70 00:00      
         why so complex            01/01/70 00:00      
         What Compiler ?            01/01/70 00:00      
            Compiler.KEIL            01/01/70 00:00      
         general idea            01/01/70 00:00      
            Diodes to prevent ghosting            01/01/70 00:00      
    Algorithm for Scanning 4*4 Keypad            01/01/70 00:00      
      thanks            01/01/70 00:00      
         If you'd searched, you'd have had this            01/01/70 00:00      
            Search term "4x4 keypad"            01/01/70 00:00      
   check this code.            01/01/70 00:00      
      Answers            01/01/70 00:00      
   Sorry kai.            01/01/70 00:00      
      keypad scanner in C            01/01/70 00:00      

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