State Machine-based Pedestrian Crossing Simulator

[fj604 34]

As promised: a pedestrian crossing simulator - requires a 74HC595 shift register (though I could have done this without it)

 

/*
* State Machine demo for MSP430
* Simulates a UK pedestrian crossing with sound
* http://en.wikipedia.org/wiki/Pelican_crossing
* Requires a 74HC595 shift register and an optional piezo speaker
* WDT timer is used to control traffic light phases and beeps
* Timer_A0 used as a beep frequency generator
*/

#include 

#define TF 23		// Approx. WDT ticks per second 

// Pin definitions
// 74HC595: Data - P1.4, Clock = P1.5, Latch = P1.2 

#define PIN_DATA	BIT4
#define PIN_CLOCK	BIT5
#define PIN_LATCH	BIT2

// Pedestrian button on P1.7
#define PIN_BUTTON	BIT7

// Piezo speaker on P1.1
#define PIN_SPEAKER	BIT1

// LED connections for 74HC595
// T = traffic, P = pedestrian
#define T_RED		BIT0
#define T_AMBER		BIT1
#define	T_GREEN		BIT2
#define	P_RED		BIT3
#define	P_GREEN		BIT4
#define P_WAIT		BIT5

#define DEL_P_MIN		    TF*20	// Minimum time for traffic to stay green
#define DEL_T_AMBER 		TF*2	// Traffic amber phase
#define DEL_T_RED			TF*2	// Traffic red phase
#define DEL_P_GREEN			TF*8	// Pedestrian green phase
#define DEL_P_GREEN_FLASH	TF*4	// Pedestrian green / traffic amber flashing phase

#define FREQ 		4000			// Beep frequency x 2
#define BEEP_D 		3				// Beep duration in ticks
#define FLASH_D		10				// Flash duration in ticks			
#define SMCLK 		1000000			// SMCLK frequency

static enum {
INIT = 0,						// Init phase
TRAF_GREEN = 1,					// Traffic green
PED_WAITING = 2,				// Pedestrian waiting
TRAF_AMBER = 3,					// Traffic amber, pedestrian red
TRAF_RED = 4,					// Traffic red, pedestrian red
PED_GREEN = 5,					// Traffic red, pedestrian green
PED_GREEN_FLASH = 6				// Traffic amber flashing, pedestrian green flashing
} state=INIT;

unsigned char lights=0, button=0;

void main(void)
{
// Set up timers
// WDT used for light phases and timing beeps
// Timer_A used for beeps frequency

   BCSCTL1 = CALBC1_1MHZ;                  // Set DCO
   DCOCTL = CALDCO_1MHZ;

 	BCSCTL3 |= LFXT1S_2;					// 12khz VLOCLK for ACLK
	WDTCTL =  WDTPW | WDTTMSEL | WDTSSEL | WDTIS1;
											// Interval timer mode, ACLK,
											// 12 khz / 512 ~ 23 Hz  
IE1 |= WDTIE;                           // Enable WDT interrupt
P1SEL |= PIN_SPEAKER;					// PIN_SPEAKER to alternative output (CO0)
TACCTL0 = OUTMOD_0;						// OUT output mode
TACCR0 = SMCLK / FREQ;					// Set beep frequency
TACTL = TASSEL_2 | MC_0;				// SMCLK, stop timer

// Set up interrupt for button
P1OUT &= ~PIN_BUTTON;					// Pull button pin down
P1REN = PIN_BUTTON;						//	Enable resistor on button pin
P1IES &= ~PIN_BUTTON;					// Lo/Hi Edge
P1IE |= PIN_BUTTON;						// Enable interrupt
P1IFG &= ~PIN_BUTTON;					// Clear interrupt flag

P1DIR |= PIN_DATA | PIN_CLOCK | PIN_LATCH | PIN_SPEAKER;	
_enable_interrupts();
_low_power_mode_0();
}

#pragma vector=WDT_VECTOR
__interrupt void watchdog_timer(void)
{
static unsigned int ticks=0, wait=0;
unsigned char new_lights = lights;
ticks++;
if (wait)
	wait--;	
switch (state)
{
	case INIT:						// First cycle - initialize lights
	new_lights = T_GREEN | P_RED;	// Traffic green, Pedestrian red
	state = TRAF_GREEN;
	break;

	case TRAF_GREEN:
	if (button)						// If button was pressed
	{
		button = 0;					// Reset button flag
		new_lights |= P_WAIT;		// Pedestrian wait light on
		state = PED_WAITING;
	}
	break;

	case PED_WAITING:
	if (wait == 0)					// If interval expired
	{
		new_lights = T_AMBER | P_RED | P_WAIT;	// Traffic amber, Pedestrian red + wait
		wait = DEL_T_AMBER;			// Wait for traffic amber phase
		state = TRAF_AMBER;
	}
	break;

	case TRAF_AMBER:
	if (wait == 0)					// If interval expired
	{
		new_lights = T_RED | P_RED | P_WAIT;
		wait = DEL_T_RED;
		state = TRAF_RED;
	}
	break;

	case TRAF_RED:
	if (wait == 0)
	{
		new_lights = T_RED | P_GREEN;
		wait = DEL_P_GREEN;
		TACTL |= MC_1;				// start timer to sound beeps
		state = PED_GREEN;
	}
	break;

	case PED_GREEN:
	if (ticks % BEEP_D == 0)
		TACCTL0 ^= OUTMOD_4;		// Toggle TimerA output mode OUT/Toggle for intermittent beeps
	if (wait == 0)
	{
		wait = DEL_P_GREEN_FLASH;	
		state = PED_GREEN_FLASH;
		new_lights = T_AMBER | P_GREEN;
		TACTL &= ~MC_1;				// stop timer - disable beeps
	}
	break;

	case PED_GREEN_FLASH:
	if (ticks % FLASH_D == 0)
		new_lights ^= T_AMBER | P_GREEN;	// Toggle Traffic Amber + Pedestrian Green
	if (wait == 0)
	{
		new_lights = T_GREEN | P_RED;
		wait = DEL_P_MIN;
		button = 0;
		state = TRAF_GREEN;
	}
	break;
}

if (lights != new_lights)			// Shift out new lights to 74HC595
{
	unsigned char b;
	P1OUT &= ~PIN_LATCH;			// latch to low 
	lights = new_lights; 
	for (b=0; b<8; b++)				
	{
		P1OUT &= ~PIN_CLOCK;		// clock to low
		if (lights & (BIT7 >> )		// if bit is set
			P1OUT |=  PIN_DATA;		// data pin to high
		else
			P1OUT &= ~PIN_DATA;		// data pin to low
		P1OUT |= PIN_CLOCK;			// clock to high
	}
	P1OUT |= PIN_LATCH;				// latch to high
}
}

// Port 1 interrupt service routine
#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void)
{
button = 1;
P1IFG &= ~PIN_BUTTON;					// P1.4 IFG cleared
}

[zeke 693]

Great work!

 

If you have more examples, please post them up!