// STM32 Nucleo-L031K6 HAL Blink + printf() example
// Simulation: https://wokwi.com/projects/367244067477216257

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stm32l0xx_hal.h>

// ST Nucleo Green user LED (PB3)
#define LED_PORT                GPIOB
#define LED_PIN                 GPIO_PIN_3
#define LED_PORT_CLK_ENABLE     __HAL_RCC_GPIOB_CLK_ENABLE
#define VCP_TX_Pin GPIO_PIN_2
#define VCP_RX_Pin GPIO_PIN_15

UART_HandleTypeDef huart2;

void SystemClock_Config(void);

int main(void)
{
  SystemClock_Config();
  uint32_t *p_gpio_clock_control = (uint32_t*) 0X4002102C;
  uint32_t *p_gpio_mode = (uint32_t*) 0X50000400;
  uint32_t *p_gpio_output_data = (uint32_t*) 0X50000414;
  uint32_t *p_gpio_input_data = (uint32_t*) 0X50000410;
 
  *p_gpio_clock_control |= 1 << 1;
  *p_gpio_mode &= ~(3 << 8);
  *p_gpio_mode &= ~(1 << 7);
  
  while (1) {
    uint8_t volatile is_button_pressed = (uint8_t) (*p_gpio_input_data >> 4) & 0x1;

    printf("tick %u! \n", is_button_pressed);
    if (is_button_pressed) {
      *p_gpio_output_data |= 1 << 3;
    } else {
      *p_gpio_output_data &= ~(1 << 3);
    }
  };

  return 0;
}

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};

  /** Configure the main internal regulator output voltage
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  /** Initializes the RCC Oscillators according to the specified parameters
    in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLLMUL_4;
  RCC_OscInitStruct.PLL.PLLDIV = RCC_PLLDIV_2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
                                | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART2;
  PeriphClkInit.Usart2ClockSelection = RCC_USART2CLKSOURCE_PCLK1;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
  {
    Error_Handler();
  }
}

void Error_Handler(void)
{
  /* User can add his own implementation to report the HAL error return state */
}