请教，为什么STM32L452的ADC实际采样率和理论采样率差这么多？

littleshrimp · 发表于2017-10-24 17:17

请教，为什么STM32L452的ADC实际采样率和理论采样率差这么多？ [复制链接]

本帖最后由 littleshrimp 于 2017-10-24 17:19 编辑

数据手册上说STM32L452的ADC最大支持5.33MSPS

为了验证ADC的采样率

使用一个单片机产生10KHz的方波，50%占空比

将输出连接到STM32L542的ADC输入引脚

STM32L542的ADC使用系统时钟不分频，系统时钟为80MHz

使用12位分辨率，开始的时候使用DMA方式，数据长度为4096

使用STM32Cube_FW_L4_V1.9.0中的ADC_DMA_Transfer例程

Sampling time设置为640.5cycles时采样到的波形如下

Sampling time设置为247.5 cycles时采样到的波形如下

可以看到，使用DMA时采到的数据一点规律没有

DMA测试代码

/**
******************************************************************************
* @file ADC/ADC_DMA_Transfer/Src/main.c
* @author MCD Application Team
* [url=home.php?mod=space&uid=159083]@brief[/url] This example describes how to use the DMA to convert continuously data.
******************************************************************************
* @attention
*
* <h2><center>© COPYRIGHT(c) 2017 STMicroelectronics</center></h2>
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of STMicroelectronics nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************
*/
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/** @addtogroup STM32L4xx_HAL_Examples
* @{
*/
/** @addtogroup ADC_DMA_Transfer
* @{
*/
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Definitions of data related to this example */
/* Definition of ADCx conversions data table size */
#define ADC_CONVERTED_DATA_BUFFER_SIZE ((uint32_t) 4096) /* Size of array aADCxConvertedData[] */
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* ADC handle declaration */
ADC_HandleTypeDef AdcHandle;
/* ADC channel configuration structure declaration */
ADC_ChannelConfTypeDef sConfig;
/* Variable containing ADC conversions data */
static uint16_t aADCxConvertedData[ADC_CONVERTED_DATA_BUFFER_SIZE];
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void Error_Handler(void);
/* Private typedef -----------------------------------------------------------*/
#define PERIOD_VALUE (uint32_t)(1600 - 1) /* Period Value */
#define PULSE1_VALUE (uint32_t)(PERIOD_VALUE/2) /* Capture Compare 1 Value */
#define PULSE2_VALUE (uint32_t)(PERIOD_VALUE*37.5/100) /* Capture Compare 2 Value */
#define PULSE3_VALUE (uint32_t)(PERIOD_VALUE/4) /* Capture Compare 3 Value */
#define PULSE4_VALUE (uint32_t)(PERIOD_VALUE*12.5/100) /* Capture Compare 4 Value */
/* Timer handler declaration */
TIM_HandleTypeDef TimHandle;
/* Timer Output Compare Configuration Structure declaration */
TIM_OC_InitTypeDef timConfig;
/* Counter Prescaler value */
uint32_t uhPrescalerValue = 0;
/* Private functions ---------------------------------------------------------*/
void pwm_init(void)
{
/* Compute the prescaler value to have TIM1 counter clock equal to 16000000 Hz */
uhPrescalerValue = (uint32_t)(SystemCoreClock / 16000000) - 1;
/*##-1- Configure the TIM peripheral #######################################*/
/* -----------------------------------------------------------------------
TIM1 Configuration: generate 4 PWM signals with 4 different duty cycles.
In this example TIM1 input clock (TIM1CLK) is set to APB1 clock (PCLK1),
since APB1 prescaler is equal to 1.
TIM1CLK = PCLK1
PCLK1 = HCLK
=> TIM1CLK = HCLK = SystemCoreClock
To get TIM1 counter clock at 16 MHz, the prescaler is computed as follows:
Prescaler = (TIM1CLK / TIM1 counter clock) - 1
Prescaler = ((SystemCoreClock) /16 MHz) - 1
To get TIM1 output clock at 24 KHz, the period (ARR)) is computed as follows:
ARR = (TIM1 counter clock / TIM1 output clock) - 1
= 665
TIM1 Channel1 duty cycle = (TIM1_CCR1/ TIM1_ARR + 1)* 100 = 50%
TIM1 Channel2 duty cycle = (TIM1_CCR2/ TIM1_ARR + 1)* 100 = 37.5%
TIM1 Channel3 duty cycle = (TIM1_CCR3/ TIM1_ARR + 1)* 100 = 25%
TIM1 Channel4 duty cycle = (TIM1_CCR4/ TIM1_ARR + 1)* 100 = 12.5%
Note:
SystemCoreClock variable holds HCLK frequency and is defined in system_stm32l4xx.c file.
Each time the core clock (HCLK) changes, user had to update SystemCoreClock
variable value. Otherwise, any configuration based on this variable will be incorrect.
This variable is updated in three ways:
1) by calling CMSIS function SystemCoreClockUpdate()
2) by calling HAL API function HAL_RCC_GetSysClockFreq()
3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency
----------------------------------------------------------------------- */
/* Initialize TIMx peripheral as follows:
+ Prescaler = (SystemCoreClock / 16000000) - 1
+ Period = (666 - 1)
+ ClockDivision = 0
+ Counter direction = Up
*/
TimHandle.Instance = TIMx;
TimHandle.Init.Prescaler = uhPrescalerValue;
TimHandle.Init.Period = PERIOD_VALUE;
TimHandle.Init.ClockDivision = 0;
TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;
TimHandle.Init.RepetitionCounter = 0;
if (HAL_TIM_PWM_Init(&TimHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
/*##-2- Configure the PWM channels #########################################*/
/* Common configuration for all channels */
timConfig.OCMode = TIM_OCMODE_PWM1;
timConfig.OCPolarity = TIM_OCPOLARITY_HIGH;
timConfig.OCFastMode = TIM_OCFAST_DISABLE;
timConfig.OCNPolarity = TIM_OCNPOLARITY_HIGH;
timConfig.OCNIdleState = TIM_OCNIDLESTATE_RESET;
timConfig.OCIdleState = TIM_OCIDLESTATE_RESET;
/* Set the pulse value for channel 1 */
timConfig.Pulse = PULSE1_VALUE;
if (HAL_TIM_PWM_ConfigChannel(&TimHandle, &timConfig, TIM_CHANNEL_1) != HAL_OK)
{
/* Configuration Error */
Error_Handler();
}
/* Set the pulse value for channel 2 */
timConfig.Pulse = PULSE2_VALUE;
if (HAL_TIM_PWM_ConfigChannel(&TimHandle, &timConfig, TIM_CHANNEL_2) != HAL_OK)
{
/* Configuration Error */
Error_Handler();
}
/* Set the pulse value for channel 3 */
timConfig.Pulse = PULSE3_VALUE;
if (HAL_TIM_PWM_ConfigChannel(&TimHandle, &timConfig, TIM_CHANNEL_3) != HAL_OK)
{
/* Configuration Error */
Error_Handler();
}
/* Set the pulse value for channel 4 */
timConfig.Pulse = PULSE4_VALUE;
if (HAL_TIM_PWM_ConfigChannel(&TimHandle, &timConfig, TIM_CHANNEL_4) != HAL_OK)
{
/* Configuration Error */
Error_Handler();
}
/*##-3- Start PWM signals generation #######################################*/
/* Start channel 1 */
if (HAL_TIM_PWM_Start(&TimHandle, TIM_CHANNEL_1) != HAL_OK)
{
/* PWM Generation Error */
Error_Handler();
}
/* Start channel 2 */
if (HAL_TIM_PWM_Start(&TimHandle, TIM_CHANNEL_2) != HAL_OK)
{
/* PWM Generation Error */
Error_Handler();
}
/* Start channel 3 */
if (HAL_TIM_PWM_Start(&TimHandle, TIM_CHANNEL_3) != HAL_OK)
{
/* PWM generation Error */
Error_Handler();
}
/* Start channel 4 */
if (HAL_TIM_PWM_Start(&TimHandle, TIM_CHANNEL_4) != HAL_OK)
{
/* PWM generation Error */
Error_Handler();
}
}
/**
* @brief Main program.
* @param None
* @retval None
*/
int main(void)
{
/* This sample code shows how to convert an analog input and read the converted
data using DMA transfer.
To proceed, 4 steps are required: */
/* STM32L4xx HAL library initialization:
- Configure the Flash prefetch and Buffer caches
- 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 80 MHz */
SystemClock_Config();
/* Configure LED2 */
BSP_LED_Init(LED2);
// pwm_init();
/* ### - 1 - Initialize ADC peripheral #################################### */
AdcHandle.Instance = ADCx;
if (HAL_ADC_DeInit(&AdcHandle) != HAL_OK)
{
/* ADC de-initialization Error */
Error_Handler();
}
AdcHandle.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV1; /* Synchronous clock mode, input ADC clock divided by 2*/
AdcHandle.Init.Resolution = ADC_RESOLUTION_12B; /* 12-bit resolution for converted data */
AdcHandle.Init.DataAlign = ADC_DATAALIGN_RIGHT; /* Right-alignment for converted data */
AdcHandle.Init.ScanConvMode = DISABLE; /* Sequencer disabled (ADC conversion on only 1 channel: channel set on rank 1) */
AdcHandle.Init.EOCSelection = ADC_EOC_SINGLE_CONV; /* EOC flag picked-up to indicate conversion end */
AdcHandle.Init.LowPowerAutoWait = DISABLE; /* Auto-delayed conversion feature disabled */
AdcHandle.Init.ContinuousConvMode = ENABLE; /* Continuous mode enabled (automatic conversion restart after each conversion) */
AdcHandle.Init.NbrOfConversion = 1; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.DiscontinuousConvMode = DISABLE; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.NbrOfDiscConversion = 1; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.ExternalTrigConv = ADC_SOFTWARE_START; /* Software start to trig the 1st conversion manually, without external event */
AdcHandle.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE; /* Parameter discarded because software trigger chosen */
AdcHandle.Init.DMAContinuousRequests = ENABLE; /* ADC DMA continuous request to match with DMA circular mode */
AdcHandle.Init.Overrun = ADC_OVR_DATA_OVERWRITTEN; /* DR register is overwritten with the last conversion result in case of overrun */
AdcHandle.Init.OversamplingMode = DISABLE; /* No oversampling */
/* Initialize ADC peripheral according to the passed parameters */
if (HAL_ADC_Init(&AdcHandle) != HAL_OK)
{
Error_Handler();
}
/* ### - 2 - Start calibration ############################################ */
if (HAL_ADCEx_Calibration_Start(&AdcHandle, ADC_SINGLE_ENDED) != HAL_OK)
{
Error_Handler();
}
/* ### - 3 - Channel configuration ######################################## */
sConfig.Channel = ADCx_CHANNEL; /* Sampled channel number */
sConfig.Rank = ADC_REGULAR_RANK_1; /* Rank of sampled channel number ADCx_CHANNEL */
sConfig.SamplingTime = ADC_SAMPLETIME_247CYCLES_5; /* Sampling time (number of clock cycles unit) */
sConfig.SingleDiff = ADC_SINGLE_ENDED; /* Single-ended input channel */
sConfig.OffsetNumber = ADC_OFFSET_NONE; /* No offset subtraction */
sConfig.Offset = 0; /* Parameter discarded because offset correction is disabled */
if (HAL_ADC_ConfigChannel(&AdcHandle, &sConfig) != HAL_OK)
{
Error_Handler();
}
/* ### - 4 - Start conversion in DMA mode ################################# */
if (HAL_ADC_Start_DMA(&AdcHandle,
(uint32_t *)aADCxConvertedData,
ADC_CONVERTED_DATA_BUFFER_SIZE
) != HAL_OK)
{
Error_Handler();
}
/* Infinite Loop */
while (1)
{
}
}
/**
* @brief System Clock Configuration
* The system Clock is configured as follows :
* System Clock source = PLL (MSI)
* SYSCLK(Hz) = 80000000
* HCLK(Hz) = 80000000
* AHB Prescaler = 1
* APB1 Prescaler = 1
* APB2 Prescaler = 1
* MSI Frequency(Hz) = 4000000
* PLL_M = 1
* PLL_N = 40
* PLL_R = 2
* PLL_P = 7
* PLL_Q = 4
* Flash Latency(WS) = 4
* @param None
* @retval None
*/
void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
/* MSI is enabled after System reset, activate PLL with MSI as source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
RCC_OscInitStruct.MSIState = RCC_MSI_ON;
RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
RCC_OscInitStruct.PLL.PLLM = 1;
RCC_OscInitStruct.PLL.PLLN = 40;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLP = 7;
RCC_OscInitStruct.PLL.PLLQ = 4;
if(HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
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_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if(HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
{
/* Initialization Error */
while(1);
}
}
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* AdcHandle)
{
__NOP();
}
/**
* @brief This function is executed in case of error occurrence.
* @param None
* @retval None
*/
static void Error_Handler(void)
{
/* Turn LED2 on*/
BSP_LED_On(LED2);
while (1)
{
}
}
#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(char *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 %d\r\n", file, line) */
/* Infinite loop */
while (1)
{
}
}
#endif
/**
* @}
*/
/**
* @}
*/
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

复制代码

后来使用ADC_RegularConversion_Interrupt例程

采样时间设置为640.5时，高低电平各为6个样本左右，一个周期12个样本

实际采样率为10KHz*12 = 120KSPS

理论采样率为80MHz/(640.9+12.5) = 122.5KSPS

理论和实际基本一致

采样时间设置为247.5时

采集到的数据，高电平15个样本低电平15个样本，一个周期共采集30个样本

实际采样率为10KHz*30=300KSPS

理论采样率为80MHz/(247.5+12.5) = 307.6KSPS

理论和实际基本一致

将SamplingTime改为92.5时高低电平各26个，一个周期为52个样本

实际采样率为10KHz * 52 = 520KSPS

理论采样率为80MHz / (92.5+12.5) = 761.9KSPS

实际采样率比理论低很多，是理论采样率的68.2%

将SamplingTime改为47.5时高低电平各31个，一个周期为62个样本

实际采样率为10KHz * 62= 620KSPS

理论采样率为80MHz / (47.5+12.5) = 1333.3KSPS

实际采样率比理论低很多，是理论采样率的46.5%

ADC_RegularConversion_Interrupt测试代码

/**
******************************************************************************
* @file ADC/ADC_RegularConversion_Interrupt/Src/main.c
* @author MCD Application Team
* @brief This example describes how to use an Interrupt to convert
* continuously data
******************************************************************************
* @attention
*
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of STMicroelectronics nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************
*/
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/** @addtogroup STM32L4xx_HAL_Examples
* @{
*/
/** @addtogroup ADC_RegularConversion_Interrupt
* @{
*/
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* ADC handler declaration */
ADC_HandleTypeDef AdcHandle;
/* Variable used to get converted value */
__IO uint16_t uhADCxConvertedValue[4096];
uint16_t uhADCxConvertedValueIndex = 0;
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void Error_Handler(void);
/* Private functions ---------------------------------------------------------*/
/**
* @brief Main program.
* @param None
* @retval None
*/
int main(void)
{
ADC_ChannelConfTypeDef sConfig;
/* STM32L4xx HAL library initialization:
- Configure the Flash prefetch and Buffer caches
- 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 LED2 */
BSP_LED_Init(LED2);
/* Configure the system clock to 80 MHz */
SystemClock_Config();
/*##-1- Configure the ADC peripheral #######################################*/
AdcHandle.Instance = ADCx;
if (HAL_ADC_DeInit(&AdcHandle) != HAL_OK)
{
/* ADC de-initialization Error */
Error_Handler();
}
AdcHandle.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1; /* Asynchronous clock mode, input ADC clock not divided */
AdcHandle.Init.Resolution = ADC_RESOLUTION_12B; /* 12-bit resolution for converted data */
AdcHandle.Init.DataAlign = ADC_DATAALIGN_RIGHT; /* Right-alignment for converted data */
AdcHandle.Init.ScanConvMode = DISABLE; /* Sequencer disabled (ADC conversion on only 1 channel: channel set on rank 1) */
AdcHandle.Init.EOCSelection = ADC_EOC_SINGLE_CONV; /* EOC flag picked-up to indicate conversion end */
AdcHandle.Init.LowPowerAutoWait = DISABLE; /* Auto-delayed conversion feature disabled */
AdcHandle.Init.ContinuousConvMode = ENABLE; /* Continuous mode disabled to have only 1 conversion at each conversion trig */
AdcHandle.Init.NbrOfConversion = 1; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.DiscontinuousConvMode = DISABLE; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.NbrOfDiscConversion = 1; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.ExternalTrigConv = ADC_SOFTWARE_START; /* Software start to trig the 1st conversion manually, without external event */
AdcHandle.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE; /* Parameter discarded because software trigger chosen */
AdcHandle.Init.DMAContinuousRequests = DISABLE; /* DMA one-shot mode selected (not applied to this example) */
AdcHandle.Init.Overrun = ADC_OVR_DATA_OVERWRITTEN; /* DR register is overwritten with the last conversion result in case of overrun */
AdcHandle.Init.OversamplingMode = DISABLE; /* No oversampling */
if (HAL_ADC_Init(&AdcHandle) != HAL_OK)
{
/* ADC initialization Error */
Error_Handler();
}
/*##-2- Configure ADC regular channel ######################################*/
sConfig.Channel = ADCx_CHANNEL; /* Sampled channel number */
sConfig.Rank = ADC_REGULAR_RANK_1; /* Rank of sampled channel number ADCx_CHANNEL */
sConfig.SamplingTime = ADC_SAMPLETIME_47CYCLES_5; /* Sampling time (number of clock cycles unit) */
sConfig.SingleDiff = ADC_SINGLE_ENDED; /* Single-ended input channel */
sConfig.OffsetNumber = ADC_OFFSET_NONE; /* No offset subtraction */
sConfig.Offset = 0; /* Parameter discarded because offset correction is disabled */
if (HAL_ADC_ConfigChannel(&AdcHandle, &sConfig) != HAL_OK)
{
/* Channel Configuration Error */
Error_Handler();
}
/* Run the ADC calibration in single-ended mode */
if (HAL_ADCEx_Calibration_Start(&AdcHandle, ADC_SINGLE_ENDED) != HAL_OK)
{
/* Calibration Error */
Error_Handler();
}
/*##-3- Start the conversion process #######################################*/
if (HAL_ADC_Start_IT(&AdcHandle) != HAL_OK)
{
/* Start Conversation Error */
Error_Handler();
}
/* Infinite loop */
while (1)
{
}
}
/**
* @brief System Clock Configuration
* The system Clock is configured as follows :
* System Clock source = PLL (MSI)
* SYSCLK(Hz) = 80000000
* HCLK(Hz) = 80000000
* AHB Prescaler = 1
* APB1 Prescaler = 1
* APB2 Prescaler = 1
* MSI Frequency(Hz) = 4000000
* PLL_M = 1
* PLL_N = 40
* PLL_R = 2
* PLL_P = 7
* PLL_Q = 4
* Flash Latency(WS) = 4
* @param None
* @retval None
*/
void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
/* MSI is enabled after System reset, activate PLL with MSI as source */
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
RCC_OscInitStruct.MSIState = RCC_MSI_ON;
RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
RCC_OscInitStruct.PLL.PLLM = 1;
RCC_OscInitStruct.PLL.PLLN = 40;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLP = 7;
RCC_OscInitStruct.PLL.PLLQ = 4;
if(HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
/* Initialization Error */
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_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if(HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
{
/* Initialization Error */
while(1);
}
}
/**
* @brief This function is executed in case of error occurrence.
* @param None
* @retval None
*/
static void Error_Handler(void)
{
/* Turn LED2 on */
BSP_LED_On(LED2);
while (1)
{
}
}
/**
* @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)
{
/* Get the converted value of regular channel */
uhADCxConvertedValue[uhADCxConvertedValueIndex++] = HAL_ADC_GetValue(AdcHandle);
if(uhADCxConvertedValueIndex >= 4096)
{
uhADCxConvertedValueIndex = 0;
__NOP();
}
}
#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(char *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 %d\r\n", file, line) */
/* Infinite loop */
while (1)
{
}
}
#endif
/**
* @}
*/
/**
* @}
*/
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

复制代码

dontium · 发表于2017-10-24 17:43

我也遇到这个问题。

楼主别使用库，使用直接寄存器操作试试！
特别是那些中断函数、CALL BACK，害人得很！

我用746，真的把我“气死了”，开始以为程序哪儿有问题，进入不了主循环，最后跟踪发现，一直在处理ADC中断！

littleshrimp · 发表于2017-10-24 20:03

dontium 发表于 2017-10-24 17:43
我也遇到这个问题。

楼主别使用库，使用直接寄存器操作试试！
特别是那些中断函数、CALL BACK，害人得 ...

ADC_RegularConversion_Interrupt例程应该和HAL_ADC_IRQHandler中断有关
每执行一次ADC_RegularConversion_Interrupt都要做很多判断还要清中断标志

现在只能考虑DMA，为什么使用DMA例程读到的数据会是乱的应该和使用库没有关系
估计还有哪些地方我还没弄明白，再试试看

柠檬酸钠 · 发表于2017-10-25 08:42

之前碰到过用库函数，io口刷屏，速度会比直接操作IO口要慢一点

freebsder · 发表于2017-10-25 09:26

本帖最后由 freebsder 于 2017-10-25 09:30 编辑

SAR的保持时间与外部输入电容，内部采样电容，内外阻抗等因素有关。输出处理虽然会有消耗，DMA记录本身的顺序记录不是主要影响因素。
为了印证上面的话，虽然我不用ST，特意去官网翻了一下STM32L452的DS，其中顺眼看去有2幅图应该可以说明一些问题：

最大采样需要满足，1快速通道，2外部阻抗不能超过100欧。。。
因此不谈实际电路强怼不行就往库身上推就是耍流氓。

littleshrimp · 发表于2017-10-25 11:01

freebsder 发表于 2017-10-25 09:26
SAR的保持时间与外部输入电容，内部采样电容，内外阻抗等因素有关。输出处理虽然会有消耗，DMA记录本身的顺 ...

现在来看应该不是这部分的问题
使用中断方式读到的数据虽然比理论慢很多，但最少还能达到1Msp以上
而使用DMA无论怎么设置读取到的数据都是乱的
使用DMA方式读取10KHz方波基本都是2~3个低电平2~3个高电平样本
修改采样时间和ADC时钟分频数居然不会对采集到的数据产生太大影响
甚至昨天晚上我把输入频率改成100Hz时使用DMA采样到的数据还是这样

如果把ADC引脚接在3.3V基本上是4095接在GND基本是0，这又说明ADC的输入是正常的
我还尝试过使用STM32F469I Discovery使用官方的ADC DMA例程遇到的问题和STM32L452是一样的

现在来看有可能是在DMA状态下的采样触发没有设置正确，或者还有其它地方和不使用DMA的配置有区别

huaiqiao · 发表于2017-10-26 18:15

hal的库，读起来真的很晦涩，我也不太想碰他。。。。。。
我基本都用的是标准外设库。

请教，为什么STM32L452的ADC实际采样率和理论采样率差这么多？ [复制链接]

最新回复

点评

点评

测评达人