/* ------------------------------------------------------------ */
/* switch debounce */
/*
 * 10 Jul 2014	dpa	Switch debounce example code
 *
 * 		A bumper switch is connected to the microprocessor
 * 		PORTE_DATA, pin 7, configured as an input, and pulled
 * 		high by a 4.7k resistor.  Switch closure pulls the
 * 		pin to ground.
 *
 * 		Debounce code samples the switch a 1kHz, looking
 * 		for 6 consecutive switch closures or openings.
 * 		So latency is 6ms.
 *
 * 		PORTE_DATA and PORTE_DDR are specific to the MC68332
 * 		processor.  Change these to match your micro hardware ports.
 *
 * 		Code inspired by excellent online article from: 
 * 		http://www.ganssle.com/debouncing.htm
 */
/* ------------------------------------------------------------ */

#define BUMPER 0x80	/* MC68332 PORTE pin 7 */

#define OPEN 0
#define CLOSED 1
#define SWITCH_CLOSED_DEBOUNCE 6
#define SWITCH_OPEN_DEBOUNCE 6


/* Note that debounce timing for OPEN and CLOSED can be different
 * if required by the physical switch.
 */
/* ------------------------------------------------------------ */
/* debounce state vector, called from 1kHz interrupt */

void (*switch_state)();	/* vector for debounce Finite State Machine */

/* ------------------------------------------------------------ */
/* global debounce output variable */

int bump_switch;	/* bumper switch state, read by bumper behavior code */

/* ------------------------------------------------------------ */
/* local debounce variables */

int switch_count;	/* debounce count */

/* ------------------------------------------------------------ */

void switch_state1()       /* switch open, looking for closed */
{
        void extern switch_state2();

        if ((PORTE_DATA & BUMPER) == 0)  {	/* 0 means switch has closed */
                switch_count++;
                if (switch_count > SWITCH_CLOSED_DEBOUNCE) {
                        bump_switch = CLOSED;
                        switch_count = 0;
                        switch_state = switch_state2;
                }
        } else  {
                switch_count = 0;	/* reset switch count if switch not closed or bouncing */
        }
}


/* ------------------------------------------------------------ */

void switch_state2()       /* switch closed, looking for open */
{
        if (PORTE_DATA & BUMPER) {		/* true means switch has opened */
                switch_count++;
                if (switch_count > SWITCH_OPEN_DEBOUNCE) {
                        bump_switch = OPEN;
                        switch_count = 0;
                        switch_state = switch_state1;
                }
        } else  {
                switch_count = 0;	/* reset switch count if switch not open or bouncing */
        }
}

/* ------------------------------------------------------------ */
/* switch debounce.  run from 1kHz interrupt */

void switch_debounce_service()
{
	if (switch_state) (*switch_state)();
}

/* ------------------------------------------------------------ */

int switch_init()
{
        PORTE_DDR &= 0xef;      /* set PORTE pin 7 to input */

        switch_count = 0; 	/* reset switch count */
	bump_switch = OPEN; 	/* init switch state to OPEN */
	switch_state = switch_state1;	/* init switch state looking for closed */

        return 0;
}

/* ------------------------------------------------------------ */
/* EOF */