Styjun

Using the StdPeriph Library for my STM32F4 Discovery board, I encountered a strange problem with the Debugger/Code. ( using the IAR Workbench )

The variable ADC3ConvertedValue shows 16bit values, whereas the ADC is only 12bit. In fact, they do correlate with the input voltage of the ADC, but I expected a value 2^12 - 1 max.

The problem has to be somewhere in my short code. I am using DMA in circular Mode from the Library-Example (I just changed the main() function)

Trying only a while loop from the example Code works fine, but as soon as I add my few lines, the value is corrupt.

__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);
 

For clarification, this is the example Code that works ( I just changed the main function) :

/* 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)
 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 %drn", file, line) */

 /* Infinite loop */
 while (1)
 
 

#endif

/**
 * @
 */ 

/**
 * @
 */ 

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