A Four Way Intersection Traffic Light Using STM32

#include "stm32f4xx.h"
#include <stdint.h>

// Preset delay based on clock
#define DELAY_1S 400000U    // clock speed 40MHz
#define D20 (20 * DELAY_1S) // 20 seconds delay for green
#define D05 (5 * DELAY_1S)  // 5 seconds delay for yellow transition
#define D1 (1 * DELAY_1S)   // 1 second safety delay

void delay(volatile uint32_t time) {
    while(time--);
}

void GPIO_Init(void) {
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN; // For GPIOA AND GPIOB
    GPIOA->MODER |= 0x555555; // PA0-PA11 output
}

void All_Off(void) {
    GPIOA->ODR &= ~(0xFFF); // Clear bits output 1-11
}

void SetLight(uint8_t red, uint8_t yellow, uint8_t green, char state) {
    GPIOA->ODR &= ~((1 << red) | (1 << yellow) | (1 << green));
    if (state == 'R') GPIOA->ODR |= (1 << red);    // Red
       else if (state == 'Y') GPIOA->ODR |= (1 << yellow); // Yellow
       else if (state == 'G') GPIOA->ODR |= (1 << green);  // Green
}

void SetAll(char Traffic_1, char Traffic_2, char Traffic_3, char Traffic_4) {
    SetLight(0, 1, 2, Traffic_1); // For Traffic light 1: PA0, PA1, PA2  ( southbound lights )
    SetLight(3, 4, 5, Traffic_2); // For Traffic light 2: PA3, PA4, PA5  ( westbound  lights )
    SetLight(6, 7, 8, Traffic_3); // For Traffic light 3: PA6, PA7, PA8  ( eastbound  lights )
    SetLight(9,10,11, Traffic_4); // For Traffic light 4: PA9, PA10,PA11 ( northbound lights )
	
	  // 0,3,6,9 for red light , 1,4,7,10 for yellow light, 2,5,8,11 for green light.
}

int main(void) {
    GPIO_Init();

    while (1) {
        // STEP 1: Traffic_1 green, others red
        SetAll('G','R','R','R'); 
        delay(D20);          // Traffic_1 stays green for 20s
        
        // Transition for Traffic  light_1 directly to red, Traffic_2 to yellow
        SetAll('R','Y','R','R');
        delay(D05);          // Traffic_2 yellow for 5s
        
        // STEP 2: Traffic_2 green, others red
        SetAll('R','G','R','R');
        delay(D20);          // Traffic_2 stays green for 20s
        
        // Transition for Traffic light_2 directly to red, Traffic_3 to yellow
        SetAll('R','R','Y','R');
        delay(D05);          // Traffic_3 yellow for 5s
        
        // STEP 3: Traffic_3 green, others red
        SetAll('R','R','G','R');
        delay(D20);          // Traffic_3 stays green for 20s
        
        // Transition for Traffic light_3 directly to red, Traffic_4 to yellow
        SetAll('R','R','R','Y');
        delay(D05);          // Traffic_4 yellow for 5s
        
        // STEP 4: Traffic_4 green, others red
        SetAll('R','R','R','G');
        delay(D20);          // Traffic_4 stays green for 20s
        
        // Transition for Traffic_4 directly to red, Traffic_1 to yellow
        SetAll('Y','R','R','R');
        delay(D05);          // Traffic_1 yellow for 5s
    }
}