用STM32L475设计一个倒车雷达的程序代码

设计一个倒车雷达需要以下步骤：

1. 选定合适的超声波传感器模块，并将模块连接到STM32L475的GPIO口。

2. 初始化STM32L475的ADC模块，以读取超声波传感器返回的信号。

3. 通过计算处理超声波传感器返回的信号，得到离障碍物的距离。

4. 根据距离的大小，控制STM32L475的蜂鸣器发出不同的声音。

以下是一个简单的倒车雷达的程序代码：

#include "stm32l4xx_hal.h"

#define TRIG_PIN GPIO_PIN_0
#define ECHO_PIN GPIO_PIN_1
#define TRIG_PORT GPIOA
#define ECHO_PORT GPIOA
#define BUZZER_PIN GPIO_PIN_7
#define BUZZER_PORT GPIOB

TIM_HandleTypeDef htim2;
ADC_HandleTypeDef hadc1;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM2_Init(void);
static void MX_ADC1_Init(void);

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_TIM2_Init();
  MX_ADC1_Init();

  HAL_TIM_Base_Start(&htim2);

  while (1)
  {
    // 发送10us的高电平信号
    HAL_GPIO_WritePin(TRIG_PORT, TRIG_PIN, GPIO_PIN_SET);
    HAL_Delay(10);
    HAL_GPIO_WritePin(TRIG_PORT, TRIG_PIN, GPIO_PIN_RESET);

    // 等待接收回波
    uint32_t start_time = 0, end_time = 0;
    while (HAL_GPIO_ReadPin(ECHO_PORT, ECHO_PIN) == GPIO_PIN_RESET)
    {
      start_time = __HAL_TIM_GET_COUNTER(&htim2);
    }
    while (HAL_GPIO_ReadPin(ECHO_PORT, ECHO_PIN) == GPIO_PIN_SET)
    {
      end_time = __HAL_TIM_GET_COUNTER(&htim2);
    }

    // 计算距离
    float distance = (end_time - start_time) * 1.0 / (HAL_RCC_GetHCLKFreq() / 1000000) * 343 / 2;

    // 控制蜂鸣器
    if (distance < 20)
    {
      HAL_GPIO_WritePin(BUZZER_PORT, BUZZER_PIN, GPIO_PIN_SET);
      HAL_Delay(100);
      HAL_GPIO_WritePin(BUZZER_PORT, BUZZER_PIN, GPIO_PIN_RESET);
      HAL_Delay(100);
    }
    else if (distance < 50)
    {
      HAL_GPIO_WritePin(BUZZER_PORT, BUZZER_PIN, GPIO_PIN_SET);
      HAL_Delay(500);
      HAL_GPIO_WritePin(BUZZER_PORT, BUZZER_PIN, GPIO_PIN_RESET);
      HAL_Delay(500);
    }
    else if (distance < 100)
    {
      HAL_GPIO_WritePin(BUZZER_PORT, BUZZER_PIN, GPIO_PIN_SET);
      HAL_Delay(1000);
      HAL_GPIO_WritePin(BUZZER_PORT, BUZZER_PIN, GPIO_PIN_RESET);
      HAL_Delay(1000);
    }
  }
}

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

  /** 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_NONE;
  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_HSI;
  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_0) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_ADC1_Init(void)
{
  ADC_ChannelConfTypeDef sConfig = {0};

  /** Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
  */
  sConfig.Channel = ADC_CHANNEL_6;
  sConfig.Rank = 1;
  sConfig.SamplingTime = ADC_SAMPLETIME_239CYCLES_5;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_TIM2_Init(void)
{
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};

  htim2.Instance = TIM2;
  htim2.Init.Prescaler = (SystemCoreClock / 1000000) - 1;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 0xFFFF;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
    Error_Handler();
  }
  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  // 超声波模块
  GPIO_InitStruct.Pin = TRIG_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(TRIG_PORT, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = ECHO_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(ECHO_PORT, &GPIO_InitStruct);

  // 蜂鸣器
  GPIO_InitStruct.Pin = BUZZER_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(BUZZER_PORT, &GPIO_InitStruct);
}

此代码中使用了STM32L475的TIM2定时器，用于计算超声波信号的回波时间。同时使用了ADC模块读取超声波传感器返回的信号，并计算距离。最后通过控制蜂鸣器发出不同的声音提示驾驶员。注意，此代码仅为参考，具体实现方式可能因传感器硬件和场景不同而有所调整。