Electrical – How to reconstruct input signal by using DAC

adcdacdmastm32f4

I am working on a project in which –

  1. I have to continuously monitor the the ADC input on a microcontroller(STM32F407) and
    check if the value crosses a certain threshold.
  2. If the value crosses the threshold, start a timer for 100ms.
  3. Within this period,use DMA to tranfer ADC samples to a buffer.After the period
    elapses,a periodelapsed callback will be called where I stop the timer and the ADC DMA transfer process.

I am giving an ADC input from a piezoelectric sensor and I want to send these samples onto a the output of a DAC and check on my oscilloscope if it matches with my input. But I am not sure how to do that. Can anyone guide me here?
I have configured my ADC sampling rate to about 50 microseconds and timer period to 100 milliseconds.
Here is my code – 

#include "main.h"
#include "stm32f4xx_hal.h"
#include "usb_host.h"
ADC_HandleTypeDef hadc1;
DMA_HandleTypeDef hdma_adc1;
DAC_HandleTypeDef hdac;
DMA_HandleTypeDef hdma_dac1;
I2C_HandleTypeDef hi2c1;
TIM_HandleTypeDef htim3;


/* Private variables ---------------------------------------------------------*/
int do_once;
int entry_count=0;
int interrupt_counter=0;
uint16_t raw_value = 0;
uint16_t buffer[2000]={0};
float VDDAmillivolts=0;

/* 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_I2C1_Init(void);
static void MX_ADC1_Init(void);
static void MX_DAC_Init(void);
static void MX_TIM3_Init(void);
void MX_USB_HOST_Process(void);
void errorhandle();


/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
    if(htim->Instance==TIM3)
    {
        HAL_ADC_Stop_DMA(&hadc1);
        HAL_TIM_Base_Stop_IT(&htim3);
        do_once=1;
        interrupt_counter++;

    }
}

/* USER CODE END PFP */


  * @brief  The application entry point.
  *
  * @retval None
  */
int main(void)
{


  /* 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_I2C1_Init();
  MX_USB_HOST_Init();
  MX_ADC1_Init();
  MX_DAC_Init();
  MX_TIM3_Init();


  /* Infinite loop */
  /* USER CODE BEGIN WHILE */

  while (1)
  {
        do_once =0;
        for(int index=0;index<2000;index++)
        {
            buffer[index]=0;
        }
        HAL_ADC_Start(&hadc1);
        while (!(__HAL_ADC_GET_FLAG(&hadc1,ADC_FLAG_EOC)));
        raw_value=HAL_ADC_GetValue(&hadc1);

        VDDAmillivolts=(raw_value*3000)/(0xFFF);
        if(VDDAmillivolts1>200)
        {
            entry_count++;
            HAL_TIM_Base_Start_IT(&htim3);
            while(do_once==0)
            {   

            if(HAL_ADC_Start_DMA(&hadc1,(uint32_t*)buffer,2000)!= HAL_OK)
                    errorhandle(); 
          }
      }

    }   

  /* USER CODE END WHILE */

  /**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{

  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;

    /**Configure the main internal regulator output voltage 
    */
  __HAL_RCC_PWR_CLK_ENABLE();

  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

    /**Initializes the CPU, AHB and APB busses clocks 
    */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 8;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 7;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Initializes the CPU, AHB and APB busses clocks 
    */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV4;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure the Systick interrupt time 
    */
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

    /**Configure the Systick 
    */
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

  /* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}

/* ADC1 init function */
static void MX_ADC1_Init(void)
{

  ADC_ChannelConfTypeDef sConfig;

    /**Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion) 
    */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV2;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = ENABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time. 
    */
  sConfig.Channel = ADC_CHANNEL_1;
  sConfig.Rank = 1;
  sConfig.SamplingTime = ADC_SAMPLETIME_480CYCLES;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

/* DAC init function */
static void MX_DAC_Init(void)
{

  DAC_ChannelConfTypeDef sConfig;

    /**DAC Initialization 
    */
  hdac.Instance = DAC;
  if (HAL_DAC_Init(&hdac) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**DAC channel OUT1 config 
    */
  sConfig.DAC_Trigger = DAC_TRIGGER_SOFTWARE;
  sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
  if (HAL_DAC_ConfigChannel(&hdac, &sConfig, DAC_CHANNEL_1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

    /**DAC channel OUT2 config 
    */
  if (HAL_DAC_ConfigChannel(&hdac, &sConfig, DAC_CHANNEL_2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

/* I2C1 init function */
static void MX_I2C1_Init(void)
{

  hi2c1.Instance = I2C1;
  hi2c1.Init.ClockSpeed = 100000;
  hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c1.Init.OwnAddress1 = 0;
  hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c1.Init.OwnAddress2 = 0;
  hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

/* TIM3 init function */
static void MX_TIM3_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 8399;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 999;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

/** 
  * Enable DMA controller clock
  */
static void MX_DMA_Init(void) 
{
  /* DMA controller clock enable */
  __HAL_RCC_DMA2_CLK_ENABLE();
  __HAL_RCC_DMA1_CLK_ENABLE();

  /* DMA interrupt init */
  /* DMA1_Stream5_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA1_Stream5_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Stream5_IRQn);
  /* DMA2_Stream0_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA2_Stream0_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA2_Stream0_IRQn);

}

/** Configure pins as 
        * Analog 
        * Input 
        * Output
        * EVENT_OUT
        * EXTI
     PC3   ------> I2S2_SD
     PA6   ------> SPI1_MISO
     PA7   ------> SPI1_MOSI
     PB10   ------> I2S2_CK
     PC7   ------> I2S3_MCK
     PC10   ------> I2S3_CK
     PC12   ------> I2S3_SD
*/
static void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct;

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOE_CLK_ENABLE();
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOH_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(CS_I2C_SPI_GPIO_Port, CS_I2C_SPI_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(OTG_FS_PowerSwitchOn_GPIO_Port, OTG_FS_PowerSwitchOn_Pin, GPIO_PIN_SET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOD, LD4_Pin|LD3_Pin|LD5_Pin|LD6_Pin 
                          |Audio_RST_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : CS_I2C_SPI_Pin */
  GPIO_InitStruct.Pin = CS_I2C_SPI_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(CS_I2C_SPI_GPIO_Port, &GPIO_InitStruct);

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

  /*Configure GPIO pin : PDM_OUT_Pin */
  GPIO_InitStruct.Pin = PDM_OUT_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF5_SPI2;
  HAL_GPIO_Init(PDM_OUT_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : B1_Pin */
  GPIO_InitStruct.Pin = B1_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_EVT_RISING;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(B1_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pins : SPI1_MISO_Pin SPI1_MOSI_Pin */
  GPIO_InitStruct.Pin = SPI1_MISO_Pin|SPI1_MOSI_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF5_SPI1;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  /*Configure GPIO pin : BOOT1_Pin */
  GPIO_InitStruct.Pin = BOOT1_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(BOOT1_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : CLK_IN_Pin */
  GPIO_InitStruct.Pin = CLK_IN_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF5_SPI2;
  HAL_GPIO_Init(CLK_IN_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pins : LD4_Pin LD3_Pin LD5_Pin LD6_Pin 
                           Audio_RST_Pin */
  GPIO_InitStruct.Pin = LD4_Pin|LD3_Pin|LD5_Pin|LD6_Pin 
                          |Audio_RST_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

  /*Configure GPIO pins : I2S3_MCK_Pin I2S3_SCK_Pin I2S3_SD_Pin */
  GPIO_InitStruct.Pin = I2S3_MCK_Pin|I2S3_SCK_Pin|I2S3_SD_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF6_SPI3;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  /*Configure GPIO pin : OTG_FS_OverCurrent_Pin */
  GPIO_InitStruct.Pin = OTG_FS_OverCurrent_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(OTG_FS_OverCurrent_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : MEMS_INT2_Pin */
  GPIO_InitStruct.Pin = MEMS_INT2_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_EVT_RISING;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(MEMS_INT2_GPIO_Port, &GPIO_InitStruct);

}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @param  file: The file name as string.
  * @param  line: The line in file as a number.
  * @retval None
  */
void errorhandle()
{
    while(1)
    {
    }
}
void _Error_Handler(char *file, int line)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  while(1)
  {
  }
  /* 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 */

/**
  * @}
  */

/**
  * @}
  */

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

EDIT – Should I send the data to the DAC after each conversion of the ADC samples or after all the samples have been converted?

EDIT – In order to test it out, I have given an input of a sine wave from a signal generator and used the following piece of code. 

uint16_t buffer[3000]={0};
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
    HAL_DAC_Start_DMA(&hdac,DAC_CHANNEL_1,(uint32_t*)buffer,3000,DAC_ALIGN_12B_R);
    //HAL_Delay(1000);
}
int main(void)
{
 while (1)
  {
/* USER CODE END WHILE */
  if(HAL_ADC_Start_DMA(&hadc1,(uint32_t*)buffer,3000)!= HAL_OK)
                {
                    Error_Handler();
                }
  }
}

But the ADC_DMA_START is executed only once and the code is always in the callback function. It does not return to while again. Any help would be appreciated. I at least want to be able to send a sine wave from my ADC to DAC for a start.

Best Answer

Sadly the STM32F407 does not support direct peripheral to peripheral DMA transfers (at least as per reference manual).

Luckily the ADC and the DAC are both 12 bit, so no conversion has to be done.

So the way to go is transfer the ADC samples to a memory location and transfer the samples then into the DAC, which can be done by another DMA stream.

For that to work you need a timer to trigger the DAC update as the DAC is a consuming peripheral without an internal sample clock and will not generate DMA transfer requests on its own. There are several timers available which can be used as trigger.

If you want, you can also synchronize the ADC sampling and the DAC output by using the same timer as a trigger source for the ADC and the DAC. That would probably also work in place, that is only using one memory address as the DMA would transfer the value to the DAC first (no wait time) and then the value of the ADC sample would be transferred there. The DAC value will lag behind one sample.

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