How to do a adc conversion every 1us with Nucleo-F303K8?

Question

Im using the STM32 Cube IDE. What I tried now is enable MSM in TIM2 and output_compare_no_output on Channel 1 and select "Reset" as the Trigger Event. Then I went to ADC1 and enabled Regular_Conversion_Mode, set Number_Of_Conversions to 1 and the External_Trigger_Conversion_Source to Timer 2 Trigger Out event. After that I set up a DMA in circular mode that pushes half-words to a RAM buffer. For testing I've set the frequency of the timer a lot lower (10Hz) and send some ADC readings from the buffer via UART in the ConvHalfCoplt and ConvCoplt complete callbacks. But at the moment it does not work. Can you think about any mistakes in my approach ?

#include "main.h"

#include <stdio.h>
#include <string.h>

#define ADC_BUF_LEN 4096
ADC_HandleTypeDef hadc1;
DMA_HandleTypeDef hdma_adc1;

DAC_HandleTypeDef hdac1;
DMA_HandleTypeDef hdma_dac1_ch1;

TIM_HandleTypeDef htim2;

UART_HandleTypeDef huart2;

/* USER CODE BEGIN PV */

uint8_t adc_buf[ADC_BUF_LEN];
char msg[16];

/* 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_USART2_UART_Init(void);
static void MX_ADC1_Init(void);
static void MX_DAC1_Init(void);
static void MX_TIM2_Init(void);

/* Private user code ---------------------------------------------------------*/

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_DMA_Init();
  MX_USART2_UART_Init();
  MX_ADC1_Init();
  MX_DAC1_Init();
  MX_TIM2_Init();
  /* USER CODE BEGIN 2 */

  HAL_TIM_Base_Start(&htim2);
  HAL_ADC_Start_DMA(&hadc1, (uint32_t*) adc_buf, ADC_BUF_LEN);

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL4;
  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_HSI;
  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_0) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC12;
  PeriphClkInit.Adc12ClockSelection = RCC_ADC12PLLCLK_DIV16;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief ADC1 Initialization Function
  * @param None
  * @retval None
  */
static void MX_ADC1_Init(void)
{
  ADC_MultiModeTypeDef multimode = {0};
  ADC_ChannelConfTypeDef sConfig = {0};

  /** Common config
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_RISING;
  hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T2_TRGO;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc1.Init.LowPowerAutoWait = DISABLE;
  hadc1.Init.Overrun = ADC_OVR_DATA_OVERWRITTEN;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure the ADC multi-mode
  */
  multimode.Mode = ADC_MODE_INDEPENDENT;
  if (HAL_ADCEx_MultiModeConfigChannel(&hadc1, &multimode) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_1;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SingleDiff = ADC_SINGLE_ENDED;
  sConfig.SamplingTime = ADC_SAMPLETIME_1CYCLE_5;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 0;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief DAC1 Initialization Function
  * @param None
  * @retval None
  */

/**
  * @brief TIM2 Initialization Function
  * @param None
  * @retval None
  */
static void MX_TIM2_Init(void)
{

  /* USER CODE BEGIN TIM2_Init 0 */

  /* USER CODE END TIM2_Init 0 */

  TIM_MasterConfigTypeDef sMasterConfig = {0};
  TIM_OC_InitTypeDef sConfigOC = {0};

  /* USER CODE BEGIN TIM2_Init 1 */

  /* USER CODE END TIM2_Init 1 */
  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 800 - 1;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 1000 - 1;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_OC_Init(&htim2) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_ENABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sConfigOC.OCMode = TIM_OCMODE_TIMING;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_OC_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM2_Init 2 */

  /* USER CODE END TIM2_Init 2 */

}

/**
  * @brief USART2 Initialization Function
  * @param None
  * @retval None
  */
static void MX_USART2_UART_Init(void)
{

  /* USER CODE BEGIN USART2_Init 0 */

  /* USER CODE END USART2_Init 0 */

  /* USER CODE BEGIN USART2_Init 1 */

  /* USER CODE END USART2_Init 1 */
  huart2.Instance = USART2;
  huart2.Init.BaudRate = 38400;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART2_Init 2 */

  /* USER CODE END USART2_Init 2 */

}

/**
  * Enable DMA controller clock
  */
static void MX_DMA_Init(void)
{

  /* DMA controller clock enable */
  __HAL_RCC_DMA1_CLK_ENABLE();

  /* DMA interrupt init */
  /* DMA1_Channel1_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA1_Channel1_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Channel1_IRQn);
  /* DMA1_Channel3_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA1_Channel3_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Channel3_IRQn);

}

/**
  * @brief GPIO Initialization Function
  * @param None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOF_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_RESET);

  /*Configure GPIO pin : PB3 */
  GPIO_InitStruct.Pin = GPIO_PIN_3;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

}

/* USER CODE BEGIN 4 */

// Called when first half of buffer is filled
void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef* hadc){
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_SET);
  sprintf(msg, "%ho\r\n", adc_buf[0]);
  HAL_UART_Transmit(&huart2, (uint8_t*) msg, strlen(msg), HAL_MAX_DELAY);
}
// Called when buffer is completely filled
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc){
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_RESET);
  sprintf(msg, "%ho\r\n", adc_buf[ADC_BUF_LEN / 2]);
  HAL_UART_Transmit(&huart2, (uint8_t*) msg, strlen(msg), HAL_MAX_DELAY);
}

/* 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 */

  /* 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,
     tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

############################################################################## Old: ##############################################################################

What I tried so far is configuring TIM2 to reset every microsecond and start a conversion in the interupt callback:

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim){
  // Check which timer triggered this callback
  if (htim == &htim2){
    HAL_ADC_Start(&hadc1);
    HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
    adc_val = HAL_ADC_GetValue(&hadc1);
  }
}

But as far as I know PollForConversion can take some time.

Is it better to create a buffer and use DMA to constantly transfer data from the ADC to the buffer and read a value from there every microsecond ? Wouldn't I read "old" data that way ?

Answer 1

Running an ADC conversion every 1us is quite a challenging task, with the STM32F3 MCU core running at max. 72MHz "only". Therefore you should solve this task using hardware functionality only:

1. set up a timer to create a trigger output event every 1us (see description of Master mode selection in TIM control register of Reference Manual). Instead of generating an interrupt your timer can generate a trigger output on an update event:
   • set Master mode selection bits MSM in TIM2_CR2 to 010 (Update).
   • bit MSM in TIM2_SMCR should stay at 0
2. set up the ADC to run a conversion when triggered by the external trigger generated by the timer (see section Conversion on external trigger in ADC chapter of Reference Manual):
   • set EXTEN to 01 (HW trigger on rising edge) in ADC1_CFGR
   • set EXTSEL to 1011 (TIM2_TRGO event) in ADC1_CFGR
3. set up the ADC to generate a DMA request after each conversion (see section Managing conversions using the DMA in ADC chapter of Reference Manual)
4. set up DMA to store data read from ADC into a RAM buffer (see chapter on DMA controller in Reference Manual). I recommend running the DMA channel in circular mode on a large RAM buffer. This avoids any necessity to reconfigure the DMA during runtime.

With this setup, you can use all MCU clock cycles on processing the large amount of data generated by the ADC in this setup (1 MByte / s). You can either poll the DMA controller to check for new data or use the DMA flags Half Transfer Complete and Transfer Complete to be notified by IRQ each time half of the buffer is filled with new data.

You will have to study the documentation of ADC, Timer and DMA quite a lot to get this setup running - but it is worth the effort since it will solve your task neatly!