@par Example Description
How to use the ADC3 and DMA to transfer continuously converted data from ADC3 to memory.
The ADC3 is configured to convert continuously ADC_CHANNEL_8.
Each time an end of conversion occurs the DMA transfers, in circular mode, the converted data from ADC3 DR register to the uhADCxConvertedValue variable.
The uhADCxConvertedValue read value is coded on 12 bits, the Vref+ reference voltage is connected on the board to VDD (+3.3V), the Vref- reference voltage is connected on the board to the ground.
To convert the read value in volts, here is the equation to apply :
Voltage = uhADCxConvertedValue * (Vref+ - Vref-) / (2^12) = uhADCxConvertedValue * 3.3 / 4096
In this example, the system clock is 216MHz, APB2 = 108MHz and ADC clock = APB2/4.
Since ADC3 clock is 27 MHz and sampling time is set to 3 cycles, the conversion
time to 12bit data is 12 cycles so the total conversion time is (12+3)/27 = 0.56us(1.57Msps).
User can vary the ADC_CHANNEL_8 voltage by applying an input voltage on pin PF10 connected to Arduino CN5 pin A1.
STM32 Eval board's LEDs can be used to monitor the transfer status:
- LED1 is ON when the conversion is complete.
- LED1 blinks when error occurs in initialization.
@par Keywords
Analog, ADC, Analog to Digital Converter, Regular Conversion, DMA, Continuous Conversion
@Note If the user code size exceeds the DTCM-RAM size or starts from internal cacheable memories (SRAM1 and SRAM2),that is shared between several processors,
then it is highly recommended to enable the CPU cache and maintain its coherence at application level.
The address and the size of cacheable buffers (shared between CPU and other masters) must be properly updated to be aligned to cache line size (32 bytes).
@Note It is recommended to enable the cache and maintain its coherence, but depending on the use case
It is also possible to configure the MPU as "Write through", to guarantee the write access coherence.
In that case, the MPU must be configured as Cacheable/Bufferable/Not Shareable.
Even though the user must manage the cache coherence for read accesses.
Please refer to the AN4838 “Managing memory protection unit (MPU) in STM32 MCUs”
Please refer to the AN4839 “Level 1 cache on STM32F7 Series”
@par Directory contents
- ADC/ADC_RegularConversion_DMA/Inc/stm32f7xx_hal_conf.h HAL configuration file
- ADC/ADC_RegularConversion_DMA/Inc/stm32f7xx_it.h DMA interrupt handlers header file
- ADC/ADC_RegularConversion_DMA/Inc/main.h Header for main.c module
- ADC/ADC_RegularConversion_DMA/Src/stm32f7xx_it.c DMA interrupt handlers
- ADC/ADC_RegularConversion_DMA/Src/main.c Main program
- ADC/ADC_RegularConversion_DMA/Src/stm32f7xx_hal_msp.c HAL MSP file
- ADC/ADC_RegularConversion_DMA/Src/system_stm32f7xx.c STM32F7xx system source file
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/** @addtogroup STM32F7xx_HAL_Examples
* @{
*/
/** @addtogroup ADC_RegularConversion_DMA
* @{
*/
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* ADC handler declaration */
ADC_HandleTypeDef AdcHandle;
/* Variable used to get converted value */
__IO uint16_t uhADCxConvertedValue = 0;
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void Error_Handler(void);
static void CPU_CACHE_Enable(void);
/* Private functions ---------------------------------------------------------*/
/**
* @brief Main program.
* @param None
* @retval None
*/
int main(void)
{
ADC_ChannelConfTypeDef sConfig;
/* Enable the CPU Cache */
CPU_CACHE_Enable();
/* STM32F7xx HAL library initialization:
- Configure the Flash prefetch
- Systick timer is configured by default as source of time base, but user
can eventually implement his proper time base source (a general purpose
timer for example or other time source), keeping in mind that Time base
duration should be kept 1ms since PPP_TIMEOUT_VALUEs are defined and
handled in milliseconds basis.
- Set NVIC Group Priority to 4
- Low Level Initialization
*/
HAL_Init();
/* Configure the system clock to 216 MHz */
SystemClock_Config();
/* Configure LED1 */
BSP_LED_Init(LED1);
/*##-1- Configure the ADC peripheral #######################################*/
AdcHandle.Instance = ADCx;
AdcHandle.Init.ClockPrescaler = ADC_CLOCKPRESCALER_PCLK_DIV4;
AdcHandle.Init.Resolution = ADC_RESOLUTION_12B;
AdcHandle.Init.ScanConvMode = DISABLE; /* Sequencer disabled (ADC conversion on only 1 channel: channel set on rank 1) */
AdcHandle.Init.ContinuousConvMode = ENABLE; /* Continuous mode enabled to have continuous conversion */
AdcHandle.Init.DiscontinuousConvMode = DISABLE; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.NbrOfDiscConversion = 0;
AdcHandle.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE; /* Conversion start trigged at each external event */
AdcHandle.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T1_CC1;
AdcHandle.Init.DataAlign = ADC_DATAALIGN_RIGHT;
AdcHandle.Init.NbrOfConversion = 1;
AdcHandle.Init.DMAContinuousRequests = ENABLE;
AdcHandle.Init.EOCSelection = DISABLE;
if (HAL_ADC_Init(&AdcHandle) != HAL_OK)
{
/* ADC initialization Error */
Error_Handler();
}
/*##-2- Configure ADC regular channel ######################################*/
sConfig.Channel = ADC_CHANNEL_8;
sConfig.Rank = 1;
sConfig.SamplingTime = ADC_SAMPLETIME_3CYCLES;
sConfig.Offset = 0;
if (HAL_ADC_ConfigChannel(&AdcHandle, &sConfig) != HAL_OK)
{
/* Channel Configuration Error */
Error_Handler();
}
/*##-3- Start the conversion process #######################################*/
if(HAL_ADC_Start_DMA(&AdcHandle, (uint32_t*)&uhADCxConvertedValue, 1) != HAL_OK)
{
/* Start Conversation Error */
Error_Handler();
}
/* Infinite loop */
while (1)
{
}
}
/**
* @brief System Clock Configuration
* The system Clock is configured as follow :
* System Clock source = PLL (HSE)
* SYSCLK(Hz) = 216000000
* HCLK(Hz) = 216000000
* AHB Prescaler = 1
* APB1 Prescaler = 4
* APB2 Prescaler = 2
* HSE Frequency(Hz) = 25000000
* PLL_M = 25
* PLL_N = 432
* PLL_P = 2
* PLL_Q = 9
* VDD(V) = 3.3
* Main regulator output voltage = Scale1 mode
* Flash Latency(WS) = 7
* @param None
* @retval None
*/
void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_OscInitTypeDef RCC_OscInitStruct;
HAL_StatusTypeDef ret = HAL_OK;
/* Enable HSE Oscillator and activate PLL with HSE as source */
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 = 25;
RCC_OscInitStruct.PLL.PLLN = 432;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 9;
ret = HAL_RCC_OscConfig(&RCC_OscInitStruct);
if(ret != HAL_OK)
{
while(1) { ; }
}
/* Activate the OverDrive to reach the 216 MHz Frequency */
ret = HAL_PWREx_EnableOverDrive();
if(ret != HAL_OK)
{
while(1) { ; }
}
/* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers */
RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | 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_DIV2;
ret = HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_7);
if(ret != HAL_OK)
{
while(1) { ; }
}
}
/**
* @brief This function is executed in case of error occurrence.
* @param None
* @retval None
*/
static void Error_Handler(void)
{
while (1)
{
/* LED1 blinks */
BSP_LED_Toggle(LED1);
HAL_Delay(20);
}
}
/**
* @brief Conversion complete callback in non blocking mode
* @param AdcHandle : AdcHandle handle
* @note This example shows a simple way to report end of conversion, and
* you can add your own implementation.
* @retval None
*/
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* AdcHandle)
{
/* Turn LED1 on: Transfer process is correct */
BSP_LED_On(LED1);
}
/**
* @brief CPU L1-Cache enable.
* @param None
* @retval None
*/
static void CPU_CACHE_Enable(void)
{
/* Enable I-Cache */
SCB_EnableICache();
/* Enable D-Cache */
SCB_EnableDCache();
}
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