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


#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);
static void MX_USART2_UART_Init(void);

void osSystickHandler(void)
{

  if ((HAL_GetTick() % 500) == 0)
  {
    HAL_GPIO_TogglePin(LED_PORT, LED_PIN);
  }
}

void initGPIO()
{
  GPIO_InitTypeDef GPIO_Config;

  GPIO_Config.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_Config.Pull = GPIO_NOPULL;
  GPIO_Config.Speed = GPIO_SPEED_FREQ_HIGH;

  GPIO_Config.Pin = LED_PIN;

  LED_PORT_CLK_ENABLE();
  HAL_GPIO_Init(LED_PORT, &GPIO_Config);

  __HAL_RCC_GPIOB_CLK_ENABLE();
}

int main(void)
{
  HAL_Init();
  SystemClock_Config();

  initGPIO();
  MX_USART2_UART_Init();

  printf("Hello, %s!\n", "Wokwi");

  HAL_GPIO_TogglePin(LED_PORT, LED_PIN);

  while (1);

  return 0;
}

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


  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);


  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();
  }

  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();
  }
}


static void MX_USART2_UART_Init(void)
{
  __HAL_RCC_GPIOA_CLK_ENABLE();


  GPIO_InitTypeDef GPIO_InitStruct = {0};
  GPIO_InitStruct.Pin = VCP_TX_Pin | VCP_RX_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF4_USART2;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
  __HAL_RCC_USART2_CLK_ENABLE();
}

void Error_Handler(void)
{

}


#define STDOUT_FILENO 1
#define STDERR_FILENO 2

int _write(int file, uint8_t *ptr, int len)
{
  switch (file)
  {
    case STDOUT_FILENO:
      HAL_UART_Transmit(&huart2, ptr, len, HAL_MAX_DELAY);
      break;

    case STDERR_FILENO:
      HAL_UART_Transmit(&huart2, ptr, len, HAL_MAX_DELAY);
      break;

    default:
      return -1;
  }

  return len;
}

{
  "version": 1,
  "author": "Uri Shaked",
  "editor": "wokwi",
  "parts": [
    {
      "type": "board-st-nucleo-l031k6",
      "id": "nucleo",
      "top": -75.59,
      "left": -217.25,
      "attrs": {}
    },
    {
      "type": "wokwi-led",
      "id": "led1",
      "top": -90,
      "left": -82.6,
      "attrs": { "color": "limegreen", "flip": "" }
    },
    {
      "type": "wokwi-resistor",
      "id": "r2",
      "top": -34.45,
      "left": -134.4,
      "attrs": { "value": "1000" }
    }
  ],
  "connections": [
    [ "$serialMonitor:TX", "nucleo:VCP_RX", "", [] ],
    [ "$serialMonitor:RX", "nucleo:VCP_TX", "", [] ], 
    [ "led1:A", "nucleo:D13", "green", [ "v144", "h-95.4" ] ],
    [ "led1:C", "nucleo:GND.9", "black", [ "v0", "h28.4", "v-48", "h-105.6", "v43.2" ] ],
    [ "nucleo:GND.2", "r2:1", "black", [ "h0" ] ],
    [ "led1:C", "r2:2", "black", [ "v0" ] ]
  ],
  "dependencies": {}
}