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蓝桥杯嵌入式快速通关篇之adc

蓝桥杯嵌入式快速通关篇之adc

ADC读取电位器电压值

近些年来，蓝桥杯嵌入式的考察越来越注重逻辑的设计，硬件部分代码量也逐渐增多，这就对如何快速地完成外设部分的程序提出了挑战。
下面，我会带大家利用官方的外设参考例程来快速完成自己的代码。

adc简介

在官方的嵌入式开发板中，adc将电压这一模拟信号转换成可以被量化的数字信号，在电阻R37上的电压范围是0~ 3.3V，转换成数字信号就是0~ 4095变量值。

官方库中的标准例程

意法半导体的标准外设库，在赛点资源包的位置

官方给的例程在如下路径

6-STM32固件库代码V3.5版\stm32f10x_stdperiph_lib\STM32F10x_StdPeriph_Lib_V3.5.0\Project\STM32F10x_StdPeriph_Examples

打开文件夹ADC,因为只使用一个adc通道，我们选择修改第二个文件 ADC1_DMA

由于是在源代码的基础上修改，所以同学们甚至可以不用明白原理，直接修改,原版完整代码如下：


#include "stm32f10x.h"

/** @addtogroup STM32F10x_StdPeriph_Examples
  * @{
  */

/** @addtogroup ADC_ADC1_DMA
  * @{
  */ 


/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define ADC1_DR_Address    ((uint32_t)0x4001244C)

/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
ADC_InitTypeDef ADC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
__IO uint16_t ADCConvertedValue;

/* Private function prototypes -----------------------------------------------*/
void RCC_Configuration(void);
void GPIO_Configuration(void);

/* Private functions ---------------------------------------------------------*/

/**
  * @brief   Main program
  * @param  None
  * @retval None
  */
int main(void)
{
  /*!< At this stage the microcontroller clock setting is already configured, 
       this is done through SystemInit() function which is called from startup
       file (startup_stm32f10x_xx.s) before to branch to application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f10x.c file
     */     
       
  /* System clocks configuration ---------------------------------------------*/
  RCC_Configuration();

  /* GPIO configuration ------------------------------------------------------*/
  GPIO_Configuration();

  /* DMA1 channel1 configuration ----------------------------------------------*/
  DMA_DeInit(DMA1_Channel1);
  DMA_InitStructure.DMA_PeripheralBaseAddr = ADC1_DR_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&ADCConvertedValue;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
  DMA_InitStructure.DMA_BufferSize = 1;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
  DMA_Init(DMA1_Channel1, &DMA_InitStructure);
  
  /* Enable DMA1 channel1 */
  DMA_Cmd(DMA1_Channel1, ENABLE);
  
  /* ADC1 configuration ------------------------------------------------------*/
  ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
  ADC_InitStructure.ADC_ScanConvMode = ENABLE;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfChannel = 1;
  ADC_Init(ADC1, &ADC_InitStructure);

  /* ADC1 regular channel14 configuration */ 
  ADC_RegularChannelConfig(ADC1, ADC_Channel_14, 1, ADC_SampleTime_55Cycles5);

  /* Enable ADC1 DMA */
  ADC_DMACmd(ADC1, ENABLE);
  
  /* Enable ADC1 */
  ADC_Cmd(ADC1, ENABLE);

  /* Enable ADC1 reset calibration register */   
  ADC_ResetCalibration(ADC1);
  /* Check the end of ADC1 reset calibration register */
  while(ADC_GetResetCalibrationStatus(ADC1));

  /* Start ADC1 calibration */
  ADC_StartCalibration(ADC1);
  /* Check the end of ADC1 calibration */
  while(ADC_GetCalibrationStatus(ADC1));
     
  /* Start ADC1 Software Conversion */ 
  ADC_SoftwareStartConvCmd(ADC1, ENABLE);

  while (1)
  {
  }
}

/**
  * @brief  Configures the different system clocks.
  * @param  None
  * @retval None
  */
void RCC_Configuration(void)
{
#if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || defined (STM32F10X_HD_VL)
  /* ADCCLK = PCLK2/2 */
  RCC_ADCCLKConfig(RCC_PCLK2_Div2); 
#else
  /* ADCCLK = PCLK2/4 */
  RCC_ADCCLKConfig(RCC_PCLK2_Div4); 
#endif
  /* Enable peripheral clocks ------------------------------------------------*/
  /* Enable DMA1 clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

  /* Enable ADC1 and GPIOC clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_GPIOC, ENABLE);
}

/**
  * @brief  Configures the different GPIO ports.
  * @param  None
  * @retval None
  */
void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* Configure PC.04 (ADC Channel14) as analog input -------------------------*/
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
}

#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 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) */

  /* Infinite loop */
  while (1)
  {
  }
}

#endif

/**
  * @}
  */ 

/**
  * @}
  */ 

/******************* (C) COPYRIGHT 2011 STMicroelectronics *****END OF FILE****/

大家看过的大多数蓝桥杯adc例程里面估计都没有用dma方法实现的,简单介绍下dma，

DMA，全称Direct Memory Access，即直接存储器访问。

DMA传输将数据从一个地址空间复制到另一个地址空间，提供在外设和存>>储器之间或者存储器和存储器之间的高速数据传输。
即DMA用来提供在外设和存储器之间或者存储器和存储器之间的高速数据传输。无须CPU的干预，通过DMA数据可以快速地移动。这就节省了CPU的资源来做其他操作。

形象地说，不需要cpu的参与，信息从一块地方传输到另一块地方，在adc这里，不需要你调用读取函数，其值也会在某个变量里被自动更新。

所以要重点关注的代码有

__IO uint16_t ADCConvertedValue;

找到__IO的定义，发现他实际是volatile,说明ADCConvertedValue这个变量可以自己变更值。实际上其储存的值就是0-4095的adc读取值

然后关注到时钟和IO口的设置，在官方开发板里，分压电阻R37连接的io口是PB0,所以时钟和引脚要有相应的修改，如下：

void RCC_Configuration(void)
{
#if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || defined (STM32F10X_HD_VL)
  /* ADCCLK = PCLK2/2 */
  RCC_ADCCLKConfig(RCC_PCLK2_Div2); 
#else
  /* ADCCLK = PCLK2/4 */
  RCC_ADCCLKConfig(RCC_PCLK2_Div4); 
#endif
  /* Enable peripheral clocks ------------------------------------------------*/
  /* Enable DMA1 clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

  /* Enable ADC1 and GPIOC clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_GPIOB, ENABLE);
}

/**
  * @brief  Configures the different GPIO ports.
  * @param  None
  * @retval None
  */
void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* Configure PC.04 (ADC Channel14) as analog input -------------------------*/
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOB, &GPIO_InitStructure);
}

RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_GPIOB, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
GPIO_Init(GPIOB, &GPIO_InitStructure);

对应代码修改这两处即可

调用（关键部分）

将ADC1_DMA文件夹中的mian.c文件复制到工程中，改名成adc.c。

将函数头 int mian()改为int adc_init(),同时将函数中的while（1）空循环删去。adc通道改成第八通道，ADC_Channel_8。

修改时钟和GPIO部分，主要是函数void RCC_Configuration(void)和void GPIO_Configuration(void)。

将变量ADCConvertedValue，用extern修饰放到自己工程的main.c中，意思是在adc.c中定义，在mian.c中调用。

完整代码如下

修改后的adc.c

#include "stm32f10x.h"

/** @addtogroup STM32F10x_StdPeriph_Examples
  * @{
  */

/** @addtogroup ADC_ADC1_DMA
  * @{
  */ 


/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define ADC1_DR_Address    ((uint32_t)0x4001244C)

/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
ADC_InitTypeDef ADC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
__IO uint16_t ADCConvertedValue;

/* Private function prototypes -----------------------------------------------*/
void RCC_Configuration(void);
void GPIO_Configuration(void);

/* Private functions ---------------------------------------------------------*/

/**
  * @brief   Main program
  * @param  None
  * @retval None
  */
void adc_init()
{
  /*!< At this stage the microcontroller clock setting is already configured, 
       this is done through SystemInit() function which is called from startup
       file (startup_stm32f10x_xx.s) before to branch to application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f10x.c file
     */     
       
  /* System clocks configuration ---------------------------------------------*/
  RCC_Configuration();

  /* GPIO configuration ------------------------------------------------------*/
  GPIO_Configuration();

  /* DMA1 channel1 configuration ----------------------------------------------*/
  DMA_DeInit(DMA1_Channel1);
  DMA_InitStructure.DMA_PeripheralBaseAddr = ADC1_DR_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&ADCConvertedValue;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
  DMA_InitStructure.DMA_BufferSize = 1;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
  DMA_Init(DMA1_Channel1, &DMA_InitStructure);
  
  /* Enable DMA1 channel1 */
  DMA_Cmd(DMA1_Channel1, ENABLE);
  
  /* ADC1 configuration ------------------------------------------------------*/
  ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
  ADC_InitStructure.ADC_ScanConvMode = ENABLE;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfChannel = 1;
  ADC_Init(ADC1, &ADC_InitStructure);

  /* ADC1 regular channel14 configuration */ 
  ADC_RegularChannelConfig(ADC1, ADC_Channel_8, 1, ADC_SampleTime_55Cycles5);
  //此处注意要将通道改为PB0对应的通道，即ADC_Channel_8

  /* Enable ADC1 DMA */
  ADC_DMACmd(ADC1, ENABLE);
  
  /* Enable ADC1 */
  ADC_Cmd(ADC1, ENABLE);

  /* Enable ADC1 reset calibration register */   
  ADC_ResetCalibration(ADC1);
  /* Check the end of ADC1 reset calibration register */
  while(ADC_GetResetCalibrationStatus(ADC1));

  /* Start ADC1 calibration */
  ADC_StartCalibration(ADC1);
  /* Check the end of ADC1 calibration */
  while(ADC_GetCalibrationStatus(ADC1));
     
  /* Start ADC1 Software Conversion */ 
  ADC_SoftwareStartConvCmd(ADC1, ENABLE);

}

/**
  * @brief  Configures the different system clocks.
  * @param  None
  * @retval None
  */
void RCC_Configuration(void)
{
#if defined (STM32F10X_LD_VL) || defined (STM32F10X_MD_VL) || defined (STM32F10X_HD_VL)
  /* ADCCLK = PCLK2/2 */
  RCC_ADCCLKConfig(RCC_PCLK2_Div2); 
#else
  /* ADCCLK = PCLK2/4 */
  RCC_ADCCLKConfig(RCC_PCLK2_Div4); 
#endif
  /* Enable peripheral clocks ------------------------------------------------*/
  /* Enable DMA1 clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

  /* Enable ADC1 and GPIOC clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_GPIOB, ENABLE);
}

/**
  * @brief  Configures the different GPIO ports.
  * @param  None
  * @retval None
  */
void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* Configure PC.04 (ADC Channel14) as analog input -------------------------*/
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOB, &GPIO_InitStructure);
}

main.c中加入的内容

调用举例,注意要使用（float）进行强制类型转换，不然输出的结果为零。

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原文链接：https://blog.csdn.net/bzd1331/article/details/122516773