关于STM32F4中ADC多通道连续采样的配置
2017-03-18 17:41
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理论基础
=========================STM32F4XX中文手册中关于ADC的介绍:
有 16 条复用通道。可以将转换分为两组:规则转换和注入转换。每个组包含一个转换序列,该序列可按任意顺序在任意通道上完成。例如,可按以下顺序对序列进行转换:ADC_IN3、ADC_IN8、ADC_IN2、ADC_IN2、ADC_IN0、ADC_IN2、ADC_IN2、ADC_IN15。
一个规则转换组最多由 16 个转换构成。必须在 ADC_SQRx 寄存器中选择转换序列的规则通道及其顺序。规则转换组中的转换总数必须写入 ADC_SQR1 寄存器中的 L[3:0] 位。
STM32F4可以实现6个通道ADC的连续转换。而问题在于采用扫描模式时,每个ADC只有一个存储寄存器ADC_DR,所以如果在下个数据来之前没有把这个数据读走就会丢失,好在有DMA传送数据。
程序配置方法
====我使用的六路ADC如下:
PA2---------ADC123 IN2 PA3---------ADC123 IN3 PA6---------ADC12 IN6 PA7---------ADC12 IN7 PC4---------ADC12 IN14 PC5---------ADC12 IN15
在STM32F4xx_adc.c文件中有如下介绍
================================================================================ How to use this driver ================================================================================
(#) Enable the ADC interface clock using RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADCx, ENABLE); //使能ADC时钟 (#) ADC pins configuration (++) Enable the clock for the ADC GPIOs using the following function: RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOx, ENABLE); (++) Configure these ADC pins in analog mode using GPIO_Init(); //使能ADC使用的引脚 (#) Configure the ADC Prescaler, conversion resolution and data alignment using the ADC_Init() function. //配置ADC分频等~~ (#) Activate the ADC peripheral using ADC_Cmd() function.
根据我需要的硬件资源,选用ADC1配置6路规则通道,使用按照过程配置函数如下:
void adc_configure(void) { GPIO_InitTypeDef GPIO_InitStructure; ADC_CommonInitTypeDef ADC_CommonInitStructure; ADC_InitTypeDef ADC_InitStructure; DMA_InitTypeDef DMA_InitStructure; RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE); //使能ADC1时钟 RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA | RCC_AHB1Periph_GPIOC | RCC_AHB1Periph_DMA2, ENABLE);//使能引脚及DMA时钟 //引脚初始化 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2|GPIO_Pin_3|GPIO_Pin_6|GPIO_Pin_7; //PA2/3/6/7 初始化 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;//模拟输入 GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;//不上下拉 GPIO_Init(GPIOA, &GPIO_InitStructure);//初始化 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4|GPIO_Pin_5; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ; GPIO_Init(GPIOC, &GPIO_InitStructure); ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;//独立模式 ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;//两采样间延迟五个时钟 ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_1; //使能 ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div4;//预分频为4分频;ADCCLK=PCLK2/4=84/4=21Mhz,最好不要超过36Mhz ADC_CommonInit(&ADC_CommonInitStructure);//初始化 ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b; ADC_InitStructure.ADC_ScanConvMode = ENABLE; ADC_InitStructure.ADC_ContinuousConvMode = ENABLE; ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None; ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right; ADC_InitStructure.ADC_NbrOfConversion = 6; ADC_Init(ADC1, &ADC_InitStructure); ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 1, ADC_SampleTime_480Cycles ); ADC_RegularChannelConfig(ADC1, ADC_Channel_3, 2, ADC_SampleTime_480Cycles ); ADC_RegularChannelConfig(ADC1, ADC_Channel_6, 3, ADC_SampleTime_480Cycles ); ADC_RegularChannelConfig(ADC1, ADC_Channel_7, 4, ADC_SampleTime_480Cycles ); ADC_RegularChannelConfig(ADC1, ADC_Channel_14, 5, ADC_SampleTime_480Cycles ); ADC_RegularChannelConfig(ADC1, ADC_Channel_15, 6, ADC_SampleTime_480Cycles ); DMA_DeInit(DMA2_Stream0); DMA_InitStructure.DMA_Channel = DMA_Channel_0; //ͨµÀÑ¡Ôñ DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&ADC1->DR;//DMAÍâÉèµØÖ· DMA_InitStructure.DMA_Memory0BaseAddr = (u32)&Adc_Value;//DMA ´æ´¢Æ÷0µØÖ· DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;//ÍâÉèµ½´æ´¢Æ÷ģʽ DMA_InitStructure.DMA_BufferSize = 0X1E;//Êý¾Ý´«ÊäÁ¿ DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;//ÍâÉè·ÇÔöÁ¿Ä£Ê½ DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;//´æ´¢Æ÷ÔöÁ¿Ä£Ê½ DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;//ÍâÉèÊý¾Ý³¤¶È:8λ DMA_InitStructure.DMA_MemoryDataSize = DMA_PeripheralDataSize_HalfWord;//´æ´¢Æ÷Êý¾Ý³¤¶È:8λ DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;// ʹÓÃÑ»·Ä£Ê½ DMA_InitStructure.DMA_Priority = DMA_Priority_High;//¸ßµÈÓÅÏȼ¶ DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable; DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; DMA_Init(DMA2_Stream0, &DMA_InitStructure);//³õʼ»¯DMA Stream //DMA_ITConfig(DMA2_Stream0,DMA_IT_TC,ENABLE); DMA_Cmd(DMA2_Stream0, ENABLE); ADC_DMARequestAfterLastTransferCmd(ADC1,ENABLE); ADC_DMACmd(ADC1, ENABLE); } }
这里关于ADC_CommonInitStructure的配置有如下说明
*** Multi mode ADCs Regular channels configuration *** ====================================================== [..] (+) Refer to "Regular channels group configuration" description to configure the ADC1, ADC2 and ADC3 regular channels. (+) Select the Multi mode ADC regular channels features (dual or triple mode) using ADC_CommonInit() function and configure the DMA mode using ADC_MultiModeDMARequestAfterLastTransferCmd() functions. (+) Read the ADCs converted values using the ADC_GetMultiModeConversionValue() function. typedef struct { uint32_t ADC_Mode; /*!< Configures the ADC to operate in independent or multi mode. This parameter can be a value of @ref ADC_Common_mode */ uint32_t ADC_Prescaler; /*!< Select the frequency of the clock to the ADC. The clock is common for all the ADCs. This parameter can be a value of @ref ADC_Prescaler */ uint32_t ADC_DMAAccessMode; /*!< Configures the Direct memory access mode for multi ADC mode. This parameter can be a value of @ref ADC_Direct_memory_access_mode_for_multi_mode */ uint32_t ADC_TwoSamplingDelay; /*!< Configures the Delay between 2 sampling phases. This parameter can be a value of @ref ADC_delay_between_2_sampling_phases */ }ADC_CommonInitTypeDef;
配置多通道时,这里ADC_CommonInitTypeDef初始化结构体中第一个参数ADC_Mode有如下选项:
#define ADC_Mode_Independent ((uint32_t)0x00000000) #define ADC_DualMode_RegSimult_InjecSimult ((uint32_t)0x00000001) #define ADC_DualMode_RegSimult_AlterTrig ((uint32_t)0x00000002) #define ADC_DualMode_InjecSimult ((uint32_t)0x00000005) #define ADC_DualMode_RegSimult ((uint32_t)0x00000006) #define ADC_DualMode_Interl ((uint32_t)0x00000007) #define ADC_DualMode_AlterTrig ((uint32_t)0x00000009) #define ADC_TripleMode_RegSimult_InjecSimult ((uint32_t)0x00000011) #define ADC_TripleMode_RegSimult_AlterTrig ((uint32_t)0x00000012) #define ADC_TripleMode_InjecSimult ((uint32_t)0x00000015) #define ADC_TripleMode_RegSimult ((uint32_t)0x00000016) #define ADC_TripleMode_Interl ((uint32_t)0x00000017) #define ADC_TripleMode_AlterTrig ((uint32_t)0x00000019)
因为只使用了一个ADC,所以选择ADC_Mode_Independent;
第二个参数ADC_Prescaler时钟分频,APB时钟为84MHz,选择4分频,则实际ADC时钟为21MHz。
第三个参数ADC_DMAAccessMode有如下定义
#define ADC_DMAAccessMode_Disabled ((uint32_t)0x00000000) /* DMA mode disabled */ #define ADC_DMAAccessMode_1 ((uint32_t)0x00004000) /* DMA mode 1 enabled (2 / 3 half-words one by one - 1 then 2 then 3)*/ #define ADC_DMAAccessMode_2 ((uint32_t)0x00008000) /* DMA mode 2 enabled (2 / 3 half-words by pairs - 2&1 then 1&3 then 3&2)*/ #define ADC_DMAAccessMode_3 ((uint32_t)0x0000C000) /* DMA mode 3 enabled (2 / 3 bytes by pairs - 2&1 then 1&3 then 3&2) */
这里ADC_DMAAccessMode_1用于12位精度,一个接一个获取;ADC_DMAAccessMode_2用于两个adc同时工作以提高ADC转换效率,ADC_DMAAccessMode_3与2大抵相同,但是精度取6位,这样速度更快。
这里我选用ADC_DMAAccessMode_1模式。
第四个参数ADC_TwoSamplingDelay用于配置两次采样间隔时间。
接下来ADC_InitStructure配置
typedef struct { uint32_t ADC_Resolution; /*!< Configures the ADC resolution dual mode. This parameter can be a value of @ref ADC_resolution */ FunctionalState ADC_ScanConvMode; /*!< Specifies whether the conversion is performed in Scan (multichannels) or Single (one channel) mode. This parameter can be set to ENABLE or DISABLE */ FunctionalState ADC_ContinuousConvMode; /*!< Specifies whether the conversion is performed in Continuous or Single mode. This parameter can be set to ENABLE or DISABLE. */ uint32_t ADC_ExternalTrigConvEdge; /*!< Select the external trigger edge and enable the trigger of a regular group. This parameter can be a value of @ref ADC_external_trigger_edge_for_regular_channels_conversion */ uint32_t ADC_ExternalTrigConv; /*!< Select the external event used to trigger the start of conversion of a regular group. This parameter can be a value of @ref ADC_extrenal_trigger_sources_for_regular_channels_conversion */ uint32_t ADC_DataAlign; /*!< Specifies whether the ADC data alignment is left or right. This parameter can be a value of @ref ADC_data_align */ uint8_t ADC_NbrOfConversion; /*!< Specifies the number of ADC conversions that will be done using the sequencer for regular channel group. This parameter must range from 1 to 16. */ }ADC_InitTypeDef;
其中第一个参数ADC_Resolution选择ADC采样精度,有如下选项:
#define ADC_Resolution_12b ((uint32_t)0x00000000) #define ADC_Resolution_10b ((uint32_t)0x01000000) #define ADC_Resolution_8b ((uint32_t)0x02000000) #define ADC_Resolution_6b ((uint32_t)0x03000000)
采样精度取最高为12位。
第二个参数ADC_ScanConvMode配置扫描模式是否开启,此处多通道当然开启
第三个参数ADC_ContinuousConvMode配置连续转换模式,为使转换完可以进行下一次转换,采用连续转换模式。
第四个参数ADC_ExternalTrigConvEdge配置外部触发源,有如下选项:
#define ADC_ExternalTrigConvEdge_None ((uint32_t)0x00000000) #define ADC_ExternalTrigConvEdge_Rising ((uint32_t)0x10000000) #define ADC_ExternalTrigConvEdge_Falling ((uint32_t)0x20000000) #define ADC_ExternalTrigConvEdge_RisingFalling ((uint32_t)0x30000000)
此处选用ADC_ExternalTrigConvEdge_None采用软件源触发而非外部触发。同样下一个参数ADC_ExternalTrigConv也无需配置
第六个参数ADC_DataAlign配置数据格式,有左对齐与右对齐两种模式,此处选用ADC_DataAlign_Right右对齐。
第七个参数ADC_NbrOfConversion配置规则通道个数。注意注释:
/*!< Specifies the number of ADC conversions that will be done using the sequencer for regular channel group. This parameter must range from 1 to 16. */
故其数据从1开始而非0,我配置六个通道填6
接下来用ADC_RegularChannelConfig()函数配置六个通道优先级。
再后面DMA配置不讲了
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