使用stm32g431的tim3的定时器写一个倒计时用lcd显示

以下是使用STM32CubeIDE和HAL库编写的倒计时程序。假设使用的LCD是16x2的，通过4位并行接口连接到STM32的GPIO口。这里的倒计时为60秒，可以根据需要进行修改。

#include "main.h"
#include "lcd.h"

TIM_HandleTypeDef htim3;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM3_Init(void);

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_TIM3_Init();
  LCD_Init();

  uint8_t count = 60;
  char str[16];

  while (1)
  {
    if (count == 0)
    {
      LCD_Clear();
      LCD_Print("Time's up!");
      HAL_TIM_Base_Stop_IT(&htim3);
      break;
    }

    sprintf(str, "Countdown: %02d", count);
    LCD_Clear();
    LCD_Print(str);
    HAL_Delay(1000);
    count--;
  }
}

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
  if (htim->Instance == TIM3)
  {
    HAL_GPIO_TogglePin(LCD_EN_GPIO_Port, LCD_EN_Pin);
  }
}

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

  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.PLLM = 1;
  RCC_OscInitStruct.PLL.PLLN = 10;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV7;
  RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
  RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
  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_2) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_TIM3_Init(void)
{
  TIM_MasterConfigTypeDef sMasterConfig = {0};

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 9999;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 999;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
  {
    Error_Handler();
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
}

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

  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  HAL_GPIO_WritePin(LCD_EN_GPIO_Port, LCD_EN_Pin, GPIO_PIN_RESET);
  HAL_GPIO_WritePin(LCD_RS_GPIO_Port, LCD_RS_Pin, GPIO_PIN_RESET);
  HAL_GPIO_WritePin(LCD_RW_GPIO_Port, LCD_RW_Pin, GPIO_PIN_RESET);

  GPIO_InitStruct.Pin = LCD_D4_Pin | LCD_D5_Pin | LCD_D6_Pin | LCD_D7_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = LCD_EN_Pin | LCD_RS_Pin | LCD_RW_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}

需要注意的是，在这个程序中，定时器TIM3的初始值为999，也就是1秒钟，而计数器从0开始计数。因此，在程序中每经过1秒钟，程序会将计数器减1，直到计数器的值为0，此时倒计时停止。同时，在每次计数器减1时，程序会将剩余时间显示在LCD上。定时器的中断函数中，使用了一个GPIO口来控制LCD的使能信号，实现了LCD的显示。