在我的STM32F4 Discovery板上使用StdPeriph库时，我在调试器/代码中遇到了一个奇怪的问题。 （使用IAR工作台）
变量ADC3ConvertedValue显示16位值，而ADC仅12位。实际上，它们确实与ADC的输入电压相关，但我希望该值最大为2 ^ 12-1。
问题必须出在我的短代码中。我从库示例中以循环模式使用DMA（我刚刚更改了main（）函数）
仅尝试使用示例代码的while循环可以正常工作，但是一旦添加几行，该值就会损坏。
__IO uint16_t ADC3ConvertedValue = 0;
__IO uint16_t ADC3ConvertedVoltage = 0;
uint32_t sum = 0;
uint16_t count = 0;
uint16_t average = 0;
float voltageSignal = 0;
void ADC3_CH12_DMA_Config(void);
int main(void)
{
ADC3_CH12_DMA_Config();
ADC_SoftwareStartConv(ADC3);
// ADC3ConvertedVoltage = ADC3ConvertedValue *3300/0xFFF;
for(count = 0; count < 5000; count++)
{
sum += ADC3ConvertedValue;
}
average = sum / count;
while(1)
{
voltageSignal = ((ADC3ConvertedValue - average) * VOLT_PER_BIT);
}
}
为澄清起见，这是有效的示例代码（我刚刚更改了主要功能）：
/* Includes ------------------------------------------------------------------*/
#include "stm32f4_discovery.h"
#include <stdio.h>
/** @addtogroup STM32F4_Discovery_Peripheral_Examples
* @{
*/
/** @addtogroup ADC_ADC3_DMA
* @{
*/
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define ADC3_DR_ADDRESS ((uint32_t)0x4001224C)
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* You can monitor the converted value by adding the variable "ADC3ConvertedValue"
to the debugger watch window */
__IO uint16_t ADC3ConvertedValue = 0;
__IO uint32_t ADC3ConvertedVoltage = 0;
/* Private function prototypes -----------------------------------------------*/
/* Private functions ---------------------------------------------------------*/
void ADC3_CH12_DMA_Config(void);
/**
* @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_stm32f4xx.s) before to branch to application main.
To reconfigure the default setting of SystemInit() function, refer to
system_stm32f4xx.c file
*/
/* ADC3 configuration *******************************************************/
/* - Enable peripheral clocks */
/* - DMA2_Stream0 channel2 configuration */
/* - Configure ADC Channel12 pin as analog input */
/* - Configure ADC3 Channel12 */
ADC3_CH12_DMA_Config();
/* Start ADC3 Software Conversion */
ADC_SoftwareStartConv(ADC3);
while (1)
{
/* convert the ADC value (from 0 to 0xFFF) to a voltage value (from 0V to 3.3V)*/
ADC3ConvertedVoltage = ADC3ConvertedValue *3300/0xFFF;
}
}
/**
* @brief ADC3 channel12 with DMA configuration
* @param None
* @retval None
*/
void ADC3_CH12_DMA_Config(void)
{
ADC_InitTypeDef ADC_InitStructure;
ADC_CommonInitTypeDef ADC_CommonInitStructure;
DMA_InitTypeDef DMA_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
/* Enable ADC3, DMA2 and GPIO clocks ****************************************/
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2 | RCC_AHB1Periph_GPIOC, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC3, ENABLE);
/* DMA2 Stream0 channel0 configuration **************************************/
DMA_InitStructure.DMA_Channel = DMA_Channel_2;
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADC3_DR_ADDRESS;
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&ADC3ConvertedValue;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
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_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
DMA_Init(DMA2_Stream0, &DMA_InitStructure);
DMA_Cmd(DMA2_Stream0, ENABLE);
/* Configure ADC3 Channel12 pin as analog input ******************************/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
GPIO_Init(GPIOC, &GPIO_InitStructure);
/* ADC Common Init **********************************************************/
ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
ADC_CommonInit(&ADC_CommonInitStructure);
/* ADC3 Init ****************************************************************/
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStructure.ADC_ScanConvMode = DISABLE;
ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_NbrOfConversion = 1;
ADC_Init(ADC3, &ADC_InitStructure);
/* ADC3 regular channel12 configuration *************************************/
ADC_RegularChannelConfig(ADC3, ADC_Channel_12, 1, ADC_SampleTime_3Cycles);
/* Enable DMA request after last transfer (Single-ADC mode) */
ADC_DMARequestAfterLastTransferCmd(ADC3, ENABLE);
/* Enable ADC3 DMA */
ADC_DMACmd(ADC3, ENABLE);
/* Enable ADC3 */
ADC_Cmd(ADC3, ENABLE);
}
#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****/