蓝桥杯嵌入式第十二届初赛题目解析
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;elseL1 = 0;LED_Hint();UART_RX();if(0 == jm)Data();elsePara();}/* 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);elseLED |= 0x0100;if(1 == L2)LED &= ~(0x02FF);elseLED |= 0x0200;LED_SET();
}
led.h
#ifndef __LED_H
#define __LED_H#include "main.h"void LED_SET(void);
void LED_Hint(void);#endifled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;elsereturn 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;elsetime += 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;elsereturn Stime;}
}//计算停车费用
double Count_Fare(uint SumTime, uchar temp)
{if(!strcmp(Car[temp].type,"CNBR"))return SumTime*CNBR;elsereturn 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");} elseprintf("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++;}elseprintf("Error\\r\\n");}elseprintf("Error\\r\\n");}}elseprintf("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idchar 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。