/**
 ******************************************************************************
 * @file           : main.c
 * @author         : Auto-generated by STM32CubeIDE
 * @brief          : Main program body
 ******************************************************************************
 * @attention
 *
 * Copyright (c) 2026 STMicroelectronics.
 * All rights reserved.
 *
 * This software is licensed under terms that can be found in the LICENSE file
 * in the root directory of this software component.
 * If no LICENSE file comes with this software, it is provided AS-IS.
 *
 ******************************************************************************
 */
#include <stdint.h>
#include "stm32f103xb.h"

/* H-bridge: IN1=PA1, IN2=PA2, ENA=PA0 */
#define IN1_PIN 1
#define IN2_PIN 2
#define EN_PIN  0

/* Buttons: DIR=PB0, RUN=PB1 */
#define BTN_DIR_PIN 0
#define BTN_RUN_PIN 1

static void delay_ms(uint16_t t){
  for(uint16_t i=0;i<t;i++){
    for(volatile uint32_t j=0;j<8000;j++){ __NOP(); }
  }
}

/* ===== 7-seg on PC0..PC6 (a..g), common cathode ===== */
static void seg_clear(void){ GPIOC->BRR = 0x7F; }

static void display_S(void){ GPIOC->BSRR = (1<<0)|(1<<2)|(1<<3)|(1<<5)|(1<<6); } // a,c,d,f,g
static void display_L(void){ GPIOC->BSRR = (1<<3)|(1<<4)|(1<<5); }               // d,e,f
static void display_R(void){ GPIOC->BSRR = (1<<2)|(1<<4)|(1<<6); }               // c,e,g (aprox)

/* ===== Motor states ===== */
typedef enum { STOP=0, LEFT, RIGHT } state_t;
static state_t current = STOP;
static state_t selected = RIGHT;
static uint8_t running = 0;

static void motor_stop(void){
  GPIOA->BRR = (1<<EN_PIN)|(1<<IN1_PIN)|(1<<IN2_PIN);
  current = STOP;
}

static void motor_left(void){
  GPIOA->BRR  = (1<<IN1_PIN);
  GPIOA->BSRR = (1<<IN2_PIN)|(1<<EN_PIN);
  current = LEFT;
}

static void motor_right(void){
  GPIOA->BRR  = (1<<IN2_PIN);
  GPIOA->BSRR = (1<<IN1_PIN)|(1<<EN_PIN);
  current = RIGHT;
}

/* Dead time: STOP -> 10ms -> new direction */
static void change_state(state_t next){
  if(next == current) return;
  motor_stop();
  delay_ms(10);
  if(next == LEFT) motor_left();
  else if(next == RIGHT) motor_right();
  else motor_stop();
}

/* ===== Debounce edge detect ===== */
typedef struct { uint8_t stable; uint8_t last; } db_t;

static uint8_t read_pin(GPIO_TypeDef* port, uint8_t pin){
  return (port->IDR & (1<<pin)) ? 1 : 0;
}

/* returns 1 only on rising edge (0->1) */
static uint8_t pressed_edge(db_t *db, GPIO_TypeDef* port, uint8_t pin){
  uint8_t raw = read_pin(port, pin);

  if(raw != db->last){
    db->last = raw;
    delay_ms(20);                 // debounce time
    raw = read_pin(port, pin);
    db->last = raw;
  }

  if(db->stable == 0 && raw == 1){
    db->stable = 1;
    return 1;
  }
  if(raw == 0) db->stable = 0;

  return 0;
}

static void gpio_init(void){
  RCC->APB2ENR |= RCC_APB2ENR_IOPAEN | RCC_APB2ENR_IOPBEN | RCC_APB2ENR_IOPCEN;

  /* PA0,PA1,PA2 output push-pull 2MHz */
  GPIOA->CRL &= ~((0xF<<(EN_PIN*4)) | (0xF<<(IN1_PIN*4)) | (0xF<<(IN2_PIN*4)));
  GPIOA->CRL |=  ((0x2<<(EN_PIN*4)) | (0x2<<(IN1_PIN*4)) | (0x2<<(IN2_PIN*4)));

  /* PB0,PB1 input pull-down */
  GPIOB->CRL &= ~((0xF<<(BTN_DIR_PIN*4)) | (0xF<<(BTN_RUN_PIN*4)));
  GPIOB->CRL |=  ((0x8<<(BTN_DIR_PIN*4)) | (0x8<<(BTN_RUN_PIN*4)));
  GPIOB->ODR &= ~((1<<BTN_DIR_PIN) | (1<<BTN_RUN_PIN));

  /* PC0..PC6 output push-pull 2MHz */
  for(int i=0;i<7;i++){
    GPIOC->CRL &= ~(0xF<<(i*4));
    GPIOC->CRL |=  (0x2<<(i*4));
  }

  motor_stop();
  seg_clear();
  display_S();
}

int main(void){
  gpio_init();

  db_t dbDir = {0,0};
  db_t dbRun = {0,0};

  while(1){
    if(pressed_edge(&dbDir, GPIOB, BTN_DIR_PIN)){
      selected = (selected == RIGHT) ? LEFT : RIGHT;
      if(running) change_state(selected);
    }

    if(pressed_edge(&dbRun, GPIOB, BTN_RUN_PIN)){
      running = !running;
      if(!running) change_state(STOP);
      else change_state(selected);
    }

    seg_clear();
    if(current == STOP) display_S();
    else if(current == RIGHT) display_R();
    else display_L();

    delay_ms(5);
  }
}