把蓝桥杯嵌入式第十二届的题目写完了，拿出来和大家一起分享。

目录

客观题

程序设计题

题目解析：

CubeMX配置

代码演示

客观题

收集的一些历年的比赛客观题和解析，以及程序设计题的PDF，在这里分享给大家。 

链接：https://pan.baidu.com/s/1hTw0inSbLjX57hOtankgKw 

 此次客观题比较简单，都是基础知识，又不理解的地方，可以在评论区留言。

程序设计题

题目解析

程序设计题用到的模块为LCD，LED，按键，串口，PWM，也都是非常熟悉的模块了。

其中PWM主要用到了一个用来改变PWM占空比的函数。

//修改PWM的占空比（CCRX）

__HAL_TIM_SET_COMPARE(&htim17, TIM_CHANNEL_1, 100);

注意：函数的参数是根据自动重装载值来设置的，例如题目要求PA7输出2KHz，占空比为20%，我设置的自动重装载值是500，那么500的20%是100，所以函数中最后一个参数填100

而串口主要是处理接收的字符串，就可以使用sscanf()函数来切割字符串，以及重写printf()函数。

函数原型：int sscanf(const char *str, const char *format, ...)

详细用法感兴趣的可以百度一下，简单说一下这个函数的用法是从字符串读取格式化输入，其实和scanf()用法差不多，举个例子吧 sscanf(rxarr,"%4s:%4s:%12s",TempCar.type,TempCar.id,TempCar.time);

以上用法是，从串口接收的字符串rxarr假如是“CNBR:A392:200202120000”,那么就把前4个字符转化成字符串赋值给TempCar.type，把中间4个字符转化成字符串赋值给TempCar.id，后面12个字符转化成字符串赋值给TempCar.time

//重定义printf函数

int fputc(int ch, FILE *f)
{
    HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xFFFF);
    return ch;
}

这次程序设计题，最主要是最难的就是停车计费，也就是时间的换算。我的想法是以一个过去的时间点为起始时间如2020年1月1日0点0分0秒，然后计算入库时间和出库时间距离起始时间有多少秒钟，之后在计算具体实现看代码吧。这样比较繁琐，但还没找到比较好的方法，如果有更好的方法也可以在评论区交流喔。

说完了解题思路就开始配置CubeMX吧。

CubeMX配置

时钟配置完了，需要按下回车（Enter）来保存。 

根据原理图配置GPIO引脚，其中lcd和led的引脚都设置为output，按键设置为input，串口使用USART1也就是PA10和PA9，PWM是PA7设置为定时器17的第一通道，需要把PD2也设置为output用来作为led的锁存器。

  在GPIO中选中按键的引脚，设置为上拉输入模式。 

在GPIO中，选中led的引脚，设置为初始状态为高电平，推挽输出模式，既不上拉也不下拉。其他引脚使用默认设置就是行。 

定时器17的通道1设置为PWM通道1，然后设置预分频器值和自动重装值以及占空比，初始默认是低电平，那就把占空比设置为0。

设置定时器3每10ms中断一次。

 设置串口1的波特率为9600，开启中断，其他默认即可。 

设置项目名字和保存路径（建议不要有中文），以及IDE的版本。

勾选这个主要是让.c和.h文件单独分开，之后就可以生成代码了，CubeMX配置就完成了，如果之后想要添加新的模块或者修改配置好了模块的值，可以直接在文件中打开CubeMX的工程进行修改，改完后再点击GENERATE CODE就行了。

代码演示

main.c

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2023 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.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "tim.h"
#include "usart.h"
#include "gpio.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "lcd.h"
#include "led.h"
#include "key.h"
#include "timer.h"
#include "show.h"
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
const float EPSINON = 0.00001;
/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */
extern uint8_t rxdata;  //串口接收数据
extern uchar btn;       //按键值
extern uchar num;       //有多少辆车进入车库
extern bool L1;         //LED1 标识
extern bool L2;         //LED2 标识

bool jm = 0;            //界面切换标识
bool Duty_Flag = 0;     //占空比切换标识
float CNBR = 3.50f, VNBR = 2.00f;   //初始停车费
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM3_Init();
  MX_TIM17_Init();
  MX_USART1_UART_Init();
  /* USER CODE BEGIN 2 */
  LCD_Init();
  LCD_Clear(Black);
  LCD_SetBackColor(Black);
  LCD_SetTextColor(White);
  
  HAL_TIM_Base_Start_IT(&htim3);
  HAL_TIM_PWM_Start(&htim17, TIM_CHANNEL_1);
  HAL_UART_Receive_IT(&huart1, &rxdata, 1);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
	  switch(btn)
	  {
		  case 1:
		  {
			  jm ^= 1;
			  btn = 0;
			  LCD_Clear(Black);
		  }
		  break;
		  case 2:
		  {
			  if(1 == jm)
			  {
				  CNBR += 0.50f;
				  VNBR += 0.50f;
			  }
			  btn = 0;
		  }
		  break;
		  case 3:
		  {
			  if(1 == jm)
			  {
				  if((CNBR - 0.50f)<=EPSINON)  //浮点数不能直接与'0'值比较
					  CNBR = 0.00f;
				  else 
					  CNBR -= 0.50f;
				  
				  if((VNBR - 0.50f)<=EPSINON)
					  VNBR = 0.00f;
				  else 
					  VNBR -= 0.50f;
			  }
			  btn = 0;
		  }
		  break;
		  case 4:
		  {
			  Duty_Flag ^= 1;
			  if(Duty_Flag)
			  {
				  __HAL_TIM_SET_COMPARE(&htim17, TIM_CHANNEL_1, 100);
				  L2 = 1;
			  }
			  else 
			  {
				  __HAL_TIM_SET_COMPARE(&htim17, TIM_CHANNEL_1, 0);
				  L2 = 0;
			  }
			  btn = 0;
		  }
		  break;
	  }
	  if(num<8)
		  L1 = 1;
	  else
		  L1 = 0;
	  
	  LED_Hint();
	  UART_RX();
	  
	  if(0 == jm)
		  Data();
	  else
		  Para();
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Configure the main internal regulator output voltage
  */
  HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1);
  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = RCC_PLLM_DIV3;
  RCC_OscInitStruct.PLL.PLLN = 20;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
  RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
  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_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

main.h

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.h
  * @brief          : Header for main.c file.
  *                   This file contains the common defines of the application.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2023 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.
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __MAIN_H
#define __MAIN_H

#ifdef __cplusplus
extern "C" {
#endif

/* Includes ------------------------------------------------------------------*/
#include "stm32g4xx_hal.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
/* USER CODE END Includes */

/* Exported types ------------------------------------------------------------*/
/* USER CODE BEGIN ET */

/* USER CODE END ET */

/* Exported constants --------------------------------------------------------*/
/* USER CODE BEGIN EC */

/* USER CODE END EC */

/* Exported macro ------------------------------------------------------------*/
/* USER CODE BEGIN EM */

/* USER CODE END EM */

/* Exported functions prototypes ---------------------------------------------*/
void Error_Handler(void);

/* USER CODE BEGIN EFP */

/* USER CODE END EFP */

/* Private defines -----------------------------------------------------------*/
/* USER CODE BEGIN Private defines */
#define uchar unsigned char
#define uint unsigned int 
/* USER CODE END Private defines */

#ifdef __cplusplus
}
#endif

#endif /* __MAIN_H */

main.h中添加了几个头文件和define。其中注意当停车费用不能为负值，但是浮点数不能直接与'0'值相比较。

key.c

#include "key.h"

Btn key[4];
uchar btn = 0;

void KEY_Scan(void)
{
	uchar i = 0;
	key[0].press = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_0);
	key[1].press = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_1);
	key[2].press = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_2);
	key[3].press = HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_0);
	
	for(i=0;i<4;i++)
	{
		switch(key[i].state)
		{
			case 0:
				if(0 == key[i].press)
					key[i].state = 1;
			break;
			
			case 1:
				if(0 == key[i].press)
				{
					key[i].state = 2;
					btn = i+1;
				}
				else 
					key[i].state = 0;
			break;
			
			case 2:
				if(1 == key[i].press)
					key[i].state = 0;
			break;
		}
	}
}

key.h

#ifndef __KEY_H
#define __KEY_H

#include "main.h"

typedef struct{
	bool press;
	uchar state;
}Btn;

void KEY_Scan(void);

#endif

led.c

#include "led.h"

bool L1;
bool L2;
uint32_t LED = 0xFF00;

void LED_SET(void)
{
	GPIOC->ODR = LED;
	HAL_GPIO_WritePin(GPIOD, GPIO_PIN_2, GPIO_PIN_SET);
	HAL_GPIO_WritePin(GPIOD, GPIO_PIN_2, GPIO_PIN_RESET);
}

void LED_Hint(void)
{
	if(1 == L1)
		LED &= ~(0x01FF);
	else
		LED |= 0x0100;
	if(1 == L2)
		LED &= ~(0x02FF);
	else
		LED |= 0x0200;
	LED_SET();
}

led.h

#ifndef __LED_H
#define __LED_H

#include "main.h"

void LED_SET(void);
void LED_Hint(void);

#endif

led使用寄存器，目的是单独控制一个LED灯时不干扰其他LED灯，使用HAL库函数，改变一个灯的值，会干扰到其他灯的显示，有没有好心人在评论区告知一下怎么使用HAL库才不会有这种情况，感谢。 

show.c

#include "show.h"

const uchar mon_table[12]={31,28,31,30,31,30,31,31,30,31,30,31};

char text[21];
uchar C = 0,V = 0;  //CNBR类型的车已入库多少辆，VNBR类型的车已入库多少辆
CarData Car[NUM] = {0};
uchar num = 0;      //有多少辆车进入车库

extern float CNBR,VNBR;
extern uchar arrow;
extern char rxarr[23];

void LCD_Print(uchar line, char *text)
{
	LCD_DisplayStringLine(line*24, (u8 *)text);
}

//检查车辆是否入库
uchar Check_Car(const char *temp_id)
{
	uchar i = 0;
	for(i=0;i<NUM;i++)
	{
		if(!(strcmp(temp_id,Car[i].id)))
			return i;
	}
	return NUM;
}

//判断是否是闰年
uchar IsLeapYear(int year)
{
	if((year%4 == 0 && year%100 == 0) || (year%400 == 0))
		return 1;
	else
		return 0;
}

//把日期换算成秒
uint32_t Time(int year,int month,int day,int hour,int minute,int second)
{
	uint32_t time;
	uchar i;
	for(i=20;i<year;i++)
	{
		if(IsLeapYear(2000+year))
			time += 366*24*60*60;
		else
			time += 365*24*60*60;
	}
	month -= 1;
	for(i=0;i<month;i++)
	{
		time += (uint32_t) mon_table[i]*24*60*60;
		if(IsLeapYear(2000+year)&&i==1)
			time += 24*60*60;
	}
	time += (uint32_t) (day-1)*24*60*60;
	time += (uint32_t) hour*60*60;
	time += (uint32_t) minute*60;
	time += (uint32_t) second;
	
	return time;
} 

//计算停车时间
uint Count_Time(const char *temp_time, uchar temp)
{
	Date tempdate,date;
	uint32_t Ptime,Ctime;
	uint Stime;
	
	sscanf(temp_time, "%2d%2d%2d%2d%2d%2d",\
	&tempdate.year,&tempdate.month,&tempdate.day,&tempdate.hour,&tempdate.minute,&tempdate.second);
	
	sscanf(Car[temp].time, "%2d%2d%2d%2d%2d%2d",\
	&date.year,&date.month,&date.day,&date.hour,&date.minute,&date.second);
	
	Ctime = Time(tempdate.year,tempdate.month,tempdate.day,tempdate.hour,tempdate.minute,tempdate.second);
	Ptime = Time(date.year,date.month,date.day,date.hour,date.minute,date.second);
	
	if(Ctime<=Ptime)
		return 0;
	else
	{
		Stime = (Ctime-Ptime)/3600;
		if((Ctime-Ptime)%3600)
			return Stime+1;
		else
			return Stime;
	}
}

//计算停车费用
double Count_Fare(uint SumTime, uchar temp)
{
	if(!strcmp(Car[temp].type,"CNBR"))
		return SumTime*CNBR;
	else
		return SumTime*VNBR;
}

//寻找停车位置
uchar Find_Location(void)
{
	uchar i;
	for(i=0;i<NUM;i++)
	{
		if(!Car[i].flag)
			break;
	}
	return i;
}

//处理串口发送的数据
void StringHandle(void)
{
	if(arrow>0)
	{
		if(22 == arrow)
		{
			uchar temp = 0;
			CarData TempCar;
			sscanf(rxarr, "%4s:%4s:%12s",TempCar.type,TempCar.id,TempCar.time);
			temp = Check_Car(TempCar.id);
			if(temp<NUM)  //车已入库
			{
				int SumTime;
				if(!(strcmp(TempCar.type,Car[temp].type)))   //检查入库车辆与出库车辆的类型是否相同
				{
					SumTime = Count_Time(TempCar.time, temp);  //计算时间是否正确
					if(SumTime)
					{						
						printf("%4s:%4s:%d:%.2lf\r\n",Car[temp].type, Car[temp].id, SumTime, Count_Fare(SumTime, temp));
						memset(&Car[temp],0,sizeof(Car[0])); //车辆出库，清除数据
						num--;
						if(!strcmp(TempCar.type,"CNBR"))
							C--;
						else if(!strcmp(TempCar.type,"VNBR"))
							V--;
					}
					else 
						printf("Error\r\n");
				}					
				else
					printf("Error\r\n");
			}
			else     //车没入库
			{
				if(num<NUM)   //车库没满
				{
					uchar L;
					L = Find_Location();   //寻找车位
					if(!strcmp(TempCar.type,"CNBR"))
					{
						TempCar.flag = 1;
						Car[L] = TempCar;
						C++;
						num++;
					}
					else if(!strcmp(TempCar.type,"VNBR"))
					{
						TempCar.flag = 1;
						Car[L] = TempCar;
						V++;
						num++;
					}
					else
						printf("Error\r\n");
				}
				else
					printf("Error\r\n");
			}
		}
		else
			printf("Error\r\n");
	}
	arrow = 0;
	memset(rxarr, 0, sizeof(rxarr));
}

void Data(void)
{
	sprintf(text, "       Data         ");
	LCD_Print(1, text);
	
	sprintf(text, "    CNBR:%d          ",C);
	LCD_Print(3, text);
	
	sprintf(text, "    VNBR:%d          ",V);
	LCD_Print(5, text);
	
	sprintf(text, "    IDLE:%d          ",NUM-C-V);
	LCD_Print(7, text);
}

void Para(void)
{
	sprintf(text, "       Para         ");
	LCD_Print(1, text);
	
	sprintf(text, "    CNBR:%.2f        ",CNBR);
	LCD_Print(3, text);
	
	sprintf(text, "    VNBR:%.2f        ",VNBR);
	LCD_Print(5, text);
}

show.h

#ifndef __SHOW_H
#define __SHOW_H

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

#define NUM 8 

typedef struct{
	char type[5];  //车类型
	char id[5];    //车id
	char time[13]; //入库时间
	bool flag;     //入库标志
}CarData;

typedef struct{
	int year;
	int month;
	int day;
	int hour;
	int minute;
	int second;
}Date;

void LCD_Print(uchar line, char *text);
uchar IsLeapYear(int year);
uint32_t Time(int year,int month,int day,int hour,int minute,int second);
uint Count_Time(const char *temp_time, uchar temp);
double Count_Fare(uint SumTime, uchar temp);
uchar Find_Location(void);
void StringHandle(void);
void Data(void);
void Para(void);

#endif

把停车时间都转化成秒钟，在判断是否合理，然后相减计算时间，不足一小时按一小时算。

timer.c

#include "timer.h"

uint8_t rxdata;  
uchar arrow = 0;
char rxarr[23];

//中断回调函数
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
	if(TIM3 == htim->Instance)
	{
		KEY_Scan();
	}
}

//串口中断回调函数
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
	if(USART1 == huart->Instance)
	{
		rxarr[arrow++] = rxdata;
		HAL_UART_Receive_IT(&huart1, &rxdata, 1);
	}
}

//判断串口有没有接受完数据
void UART_RX(void)
{
	uchar temp = 0;
	if(arrow != 0)
	{
		temp = arrow;
		HAL_Delay(1);
		if(temp == arrow)
			StringHandle();
	}
}

//重定义printf函数
int fputc(int ch, FILE *f)
{
	HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xFFFF);
	return ch;
}

timer.h

#ifndef __TIMER_H
#define __TIMER_H

#include "main.h"
#include "usart.h"
#include "key.h"
#include "show.h"

void UART_RX(void);

#endif

以上就是我修改过的文件和新添加的文件。还有lcd模块，不过不需要我们自己写，官方有提供，直接复制过来就行，注意有三个文件，别只复制lcd.c和lcd.h。

 好了，以上就是蓝桥杯嵌入式第十二届省赛的题目解析了，如果有什么问题和建议都欢迎在评论区提出来喔。