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Button debounce function - how long?

 
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j_s_connell



Joined: 02 Feb 2004
Posts: 17

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Button debounce function - how long?
PostPosted: Tue May 25, 2004 2:01 pm     Reply with quote
I have seen this routine posted several places for debouncing a pin. Its supposed to be a lot faster than using delays to wait for the pin to debounce.
If I was checking my buttons every 10ms (using a timer), will this code work for me- or should I only use it on an interrupt-on-change type button? Any comments on this routine would be great. Thanks.
Code:

int1 B2;
   signed int8 debounce_counter_B2;

   if (input(PIN_B2)) {
      if ( ++debounce_counter_B2 > 15 ) {
         B2 = 1;
         debounce_counter_B2 = 15;
      } else {
         if ( --debounce_counter_B2 < -15 ) {
            B2 = 0;
            debounce_counter_B2 = -15;
         }
      }
   }
Neutone



Joined: 08 Sep 2003
Posts: 839
Location: Houston

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PostPosted: Tue May 25, 2004 2:42 pm     Reply with quote
This one compiles better but operates on the same idea.

Code:
   
   int1 Overload_Alarm;
   int8 debounce_counter_OVERLOAD;

   if(PIN_OVERLOAD)                                         // Test the inputs status at this time
   {  if(bit_test(++debounce_counter_OVERLOAD,CounterSize)) // Aproach and test for true status
      {  --debounce_counter_OVERLOAD;                       // Remove counter overflow state
         Overload_Alarm=1;                                  // Set true status
      }                                                     // Make adjustments to the tested bit
   }                                                        // to change the counter size
   else                                                     // The input was false
   {  if(--debounce_counter_OVERLOAD==0)                    // Aproach and test for false status
      {  ++debounce_counter_OVERLOAD;                       // Remove counter from zero state
         Overload_Alarm=0;                                  // Set false status
      }
   }


I suggest CounterSize = 4; to debounce in 6 passes (60mS at 10mS per pass)
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