Question

ARM assembly lang please write code

Street Crossing - This consists of a street light (red,yellow,green row of LEDs), and a separate red and green led (walk/dont walk) and a button. When the button is pressed, the red lights light up and the green indicator for walk lights up. Eventually the green and yellow will flash saying time to walk is over, then the red for dont walk lights up, and green for traffic lights up.

Answer 1

// Traffic light w/ pedestrian button....
// (c)2013 IronCreek Software

#include <avr/io.h>
#include <avr/interrupt.h>

// (LED registers)
// NOTE: All LEDs must be hooked up on the same PORT

#define LED_PORT PORTB
#define LED_DDR DDRB
#define LED_MASK 0x1F

// LED pins
#define PED_GO 0x01
#define PED_STOP 0x02
#define GREEN 0x04
#define YELLOW 0x08
#define RED 0x10

// Pedestrian button PORT & PIN
#define BTN_PIN PIND
#define BTN_PORT PORTD
#define BTN_DDR DDRD
#define BTN 0x80

namespace
{
// Index into LED_STATES for code clarity below
#define STOP 3
#define CROSS 4
#define END_CYCLE 4
#define END_CROSS 7

// Delays are in 16.384ms units (1 = 16.384ms)
// First column has delays, second column has LED bits
const uint8_t LED_STATES[][2] = {
// Normal cycle
{ 25, PED_STOP | RED | YELLOW },
{ 200, PED_STOP | GREEN },
{ 50, PED_STOP | YELLOW },
{ 200, PED_STOP | RED, },

// Pedestrian cycle
{ 25, PED_STOP | RED },
{ 150, PED_GO | RED },
{ 25, PED_STOP | RED },
};

// Helper variables for timer
volatile uint8_t timer = 0;
volatile uint8_t change_state = 0;

ISR(TIMER0_OVF_vect)
{
if (change_state == 0 && --timer == 0)
change_state = 1;
}

void setLights(const uint8_t state)
{
LED_PORT = LED_STATES[state][1];
timer = LED_STATES[state][0];
}
}

__attribute__((OS_main)) int main()
{
uint8_t state = STOP;
uint8_t ped_request = 0;

// Setup ports
LED_DDR |= LED_MASK;
BTN_PORT |= BTN; // Enable pull-up

setLights(state);

// Start timer
TIMSK0 |= (1 << TOIE0);
TCCR0B |= (1 << CS02) | (1 << CS00);

sei();

// Main loop
for(;;)
{
if (change_state)
{
++state;

if (state == END_CYCLE || state == END_CROSS)
state = 0;

if (state == STOP && ped_request)
{
state = CROSS;
ped_request = 0;
}

setLights(state);
change_state = 0;
}

// Check pedestrian crossing button
if ((BTN_PIN & BTN) == 0 && state < CROSS)
ped_request = 1;
}
}