Button library

Button Library

The Button Library provides routines for detecting button presses and debouncing (eliminating the influence of contact flickering upon pressing a button).

Library Routines

Button

Button

Prototype	unsigned int Button(unsigned int port, unsigned int* pin, unsigned int time, unsigned int active_state);
Description	The function eliminates the influence of contact flickering upon pressing a button (debouncing). The Button pin is tested just after the function call and then again after the debouncing period has expired. If the pin was in the active state in both cases then the function returns 255 (true).
Parameters	`port:` button port address `pin:` button pin `time:` debouncing period in milliseconds `active_state:` determines what is considered as active state. Valid values: `0` (logical zero) and `1` (logical one)
Returns	`255` if the pin was in the active state for given period. `0` otherwise
Requires	Nothing.
Example	if (Button(&PORTD, 0, 1, 1)) PORTB = 0xFF; ...
Notes	None.

unsigned int oldstate;

void main() {
  ADPCFG = 0xFFFF;                             // initialize AN pins as digital
  TRISD = 0xFFFF;                              // initialize portd as input
  TRISB = 0x0000;                              // initialize portb as output

  do {
    if (Button(&PORTD, 0, 1, 1))               // detect logical one state
      oldstate = 1;
    if (oldstate && Button(&PORTD, 0, 1, 0)) { // detect logical one to logical zero transition
      LATB = ~LATB;                            // toggle portb
      oldstate = 0;
    }
  } while(1);
}

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