I am using stm32 nucleo-L552ZE-Q. The ADC reading with the DMA doesn't work

[MSadf.1]

I am trying to read an analog signal from a sensor with the ADC of my board. I set the pins correctly I think ( DMA_continuous_requests enable, circular mode, etc. ) and I started the DMA with HAL_ADC_Start_DMA outside the while(1) loop and I put a break point inside the loop to follow the updates in my buffer. BUt when I start debugging and I go inside the loop, my program block ( task constantly runing ) and my buffer doesn't get updated. How can I read the data from the sensor with the ADC ? I also have 2 call back so that I can put breakpoints when the buffer is half full and full. but nothing works I dont understand why.

[RBENF.1]

Hello @MSadf.1​,

Please provide the rest of the code using the code snippet function.

Regards,

Ryan

[MSadf.1]

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#define ADC_BUFFER_Size 4096
/* USER CODE END PD */
 
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
 
/* USER CODE END PM */
 
/* Private variables ---------------------------------------------------------*/
ADC_HandleTypeDef hadc1;
DMA_HandleTypeDef hdma_adc1;
 
UART_HandleTypeDef hlpuart1;
 
RTC_HandleTypeDef hrtc;
 
PCD_HandleTypeDef hpcd_USB_FS;
 
/* USER CODE BEGIN PV */
uint16_t adc_buffer[ADC_BUFFER_Size];
uint16_t value;
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_DMA_Init(void);
static void MX_LPUART1_UART_Init(void);
static void MX_RTC_Init(void);
static void MX_UCPD1_Init(void);
static void MX_ADC1_Init(void);
static void MX_USB_PCD_Init(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_DMA_Init();
  MX_LPUART1_UART_Init();
  MX_RTC_Init();
  MX_UCPD1_Init();
  MX_ADC1_Init();
  MX_USB_PCD_Init();
  /* USER CODE BEGIN 2 */
  HAL_ADC_Start_DMA(&hadc1, (uint32_t*)adc_buffer, ADC_BUFFER_Size);
  //HAL_ADC_Start(&hadc1);
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */
	  HAL_ADC_Start(&hadc1);
    //HAL_GPIO_WritePin(GPIOC, GPIO_PIN_7, GPIO_PIN_SET);
	  //value = HAL_ADC_GetValue(&hadc1);
	  /*if (HAL_ADC_PollForConversion(&hadc1, 1000000) == HAL_OK)
	          {
	              value = HAL_ADC_GetValue(&hadc1);
 
	          }*/
    //AL_ADC_Start(&hadc1);
    //HAL_GPIO_WritePin(GPIOC, GPIO_PIN_7, GPIO_PIN_RESET);
    //HAL_Delay(100);
    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}
/*.......*/
void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef* hadc)
{
	__NOP();
}
 
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
	__NOP();
}

I connected my sensor to the A5 pin and activated the ADC on that one. The sensor is a doppler radar sensor. When there is no movement, it send nothing, and when it detect a movement, it sends a sinus signal representing the frequency shift of the movement compared to the frequency of the signal the sensor sends. I have already an evaluation PCB that transforms this sinus into a squared signal. When there is nothing coming from the sensor, the PCB send a high analog signal ( ~3.5 V). So I would like for my board to detect each falling edge and count the time between 2 falling or rising edges.

When I debug and Look at my variables, I get the errors for adc_buffer : -var-create- unable to create variable object and target Not available and my debugger crashes after SystemClock_Config

thank you

[RBENF.1]

Hello @MSadf.1​ 

Step into the SystemClock_Config function to determine exactly where the issue is. If you can, provide your .ioc file. Also, make sure you are using the latest versions of STM32CubeMX/STM32CubeIDE.

Regards,

Ryan

[MSadf.1]

I attached the IOC file. I checked the SystemClock_Config and the problem there seemed to be solved, but my adc_buffer still won't update

Thank you for your help

[RBENF.1]

Hello @MSadf.1​,

I have reviewed your application and here's my input.

• ADC Configuration
  • you have 2 channels enabled for ADC1 but scan mode disabled. My understanding of your application is that you only need one channel.
  • Your ADC clock prescaler is too low. Your ADC clock is configured as SYSCLK which is 110MHz, while STM32L552 datasheet states it should not be over 80MHz in range 0.

 

• Even with a slightly higher prescaler, you may find that continuous ADC + DMA operation leads to an overrun error, which will stop conversion. I suggest you finetune ADC speed to suit your application needs and you should probably set Overrun data behavior to Overwritten if your application can afford it.
  • Your sampling time is quite low. Depending on your signal it could lead to inaccuracy.
• Code :
  • You can remove HAL_ADC_Start(&hadc1); from your while loop since you already started ADC_DMA in continuous mode.
  • You should launch ADC calibration beforehand.
• Application wise:
  • My understanding is that you need to measure your wave's period. A simpler method would be to use comparators and timers. You can configure a timer in capture mode to have a comparator threshold as input, then the period is the difference between two successive captured values.

Regards,

Ryan