Debounce.c

/*
  debounce.c. Snigelens version of Peter Dannegger's debounce routines.
  Debounce up to eight buttons on one port.  $Rev: 577 $
  Source: https://www.avrfreaks.net/sites/default/files/forum_attachments/debounce.pdf
 */

#include "Debounce.h"

// Bits is set to one if a debounced press is detected.
volatile uint8_t buttons_down;

// Return non-zero if a button matching mask is pressed.
uint8_t button_down(uint8_t button_mask) {
	// ATOMIC_BLOCK is needed if debounce() is called from within an ISR
	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
		// And with debounced state for a one if they match
		button_mask &= buttons_down;
		// Clear if there was a match
		buttons_down ^= button_mask;
	}
	// Return non-zero if there was a match
	return button_mask;
}

void debounce_init(void) {
	// Button pins as input
	BUTTON_DDR &= ~(BUTTON_MASK);
	// Enable pullup on buttons
	BUTTON_PORT |= BUTTON_MASK;
}