什么是ADC?

Analog to Digital Converter,将模拟信号转换成数字的模数转换器,后面可能还会接触到DAC,恰恰相反,是将数字信号转换成模拟信号。具体的原理可以自行找搜索引擎,可以得到更好的答案。

STM32 ADC的特性

参考手册给出ADC的功能十分丰富,具体如下:

  • 12 bit分辨率,量化到0-4096的范围;
  • 转换结束、注入转换结束和发生模拟看门狗事件时产生中断
  • 单次和连续转换模式
  • 从通道0到通道n的自动扫描模式
  • 自校准
  • 带内嵌数据一致性的数据对齐
  • 采样间隔可以按通道分别编程
  • 规则转换和注入转换均有外部触发选项
  • 间断模式 本文只讨论规则采样和注入采样,并给出具体的代码实现,更多细节还需要参考《STM32参考手册》

采样模式

  • 规则采样:相当于软件触发采样,可以在程序里主动调用规则采样去读取具体的ADC值;
  • 注入采样:相当于中断,所以需要具体的触发源,比如外部的信号可以触发注入采样,ADC转换成功之后,便会触发ADC中断,在中断服务子程序中,就可以读取ADC值;

触发源可以是外部信号,也可以是定时器的触发信号;标准库中注入模式的触发信号如下所示;

#define ADC_ExternalTrigConv_T1_CC1                ((uint32_t)0x00000000) /*!< For ADC1 and ADC2 */
#define ADC_ExternalTrigConv_T1_CC2                ((uint32_t)0x00020000) /*!< For ADC1 and ADC2 */
#define ADC_ExternalTrigConv_T2_CC2                ((uint32_t)0x00060000) /*!< For ADC1 and ADC2 */
#define ADC_ExternalTrigConv_T3_TRGO               ((uint32_t)0x00080000) /*!< For ADC1 and ADC2 */
#define ADC_ExternalTrigConv_T4_CC4                ((uint32_t)0x000A0000) /*!< For ADC1 and ADC2 */
#define ADC_ExternalTrigConv_Ext_IT11_TIM8_TRGO    ((uint32_t)0x000C0000) /*!< For ADC1 and ADC2 */

#define ADC_ExternalTrigConv_T1_CC3                ((uint32_t)0x00040000) /*!< For ADC1, ADC2 and ADC3 */
#define ADC_ExternalTrigConv_None                  ((uint32_t)0x000E0000) /*!< For ADC1, ADC2 and ADC3 */

#define ADC_ExternalTrigConv_T3_CC1                ((uint32_t)0x00000000) /*!< For ADC3 only */
#define ADC_ExternalTrigConv_T2_CC3                ((uint32_t)0x00020000) /*!< For ADC3 only */
#define ADC_ExternalTrigConv_T8_CC1                ((uint32_t)0x00060000) /*!< For ADC3 only */
#define ADC_ExternalTrigConv_T8_TRGO               ((uint32_t)0x00080000) /*!< For ADC3 only */
#define ADC_ExternalTrigConv_T5_CC1                ((uint32_t)0x000A0000) /*!< For ADC3 only */
#define ADC_ExternalTrigConv_T5_CC3                ((uint32_t)0x000C0000) /*!< For ADC3 only */

代码实现

基于ST标准库V3.5,实现了ADC规则采样和注入采样两种模式;

current.h

#ifndef CURRENT_H
#define CURRENT_H
#include <stdint.h>

#define RES_IA	1024	//采样电阻A
#define RES_IB	1024	//采样电阻B

/**
 * Ia--->PA0/ADC0
 *	|------------>PA2/ADC2
 * Ib--->PA1/ADC1
 *	|------------>PA3/ADC3
 */

void cur_fbk_init(void);

uint16_t cur_fbk_get_Ia(void);
uint16_t cur_fbk_get_Ia_avl(uint8_t sample_times);
uint16_t cur_fbk_get_Ib(void);
uint16_t cur_fbk_get_Ib_avl(uint8_t sample_times);

uint16_t get_inject_ia(void);
uint16_t get_inject_ib(void);


int16_t cur_fbk_get_theta(void);

#endif

current.c

#include "current.h"
#include "stm32f10x.h"
#include "stm32f10x_gpio.h"
#include "stm32f10x_adc.h"
#include "stm32f10x_rcc.h"
#include <stdint.h>

#if 1
#define IA_CHANNEL_DRI ADC_Channel_0
#define IB_CHANNEL_DRI ADC_Channel_1
#else
#define IA_CHANNEL_DRI ADC_Channel_2
#define IB_CHANNEL_DRI ADC_Channel_3
#endif

volatile uint16_t Ia_val = 0;
volatile uint16_t Ib_val = 0;

static void cur_fbk_irq_init(void){

	NVIC_InitTypeDef NVIC_InitStructure;

	/* Configure and enable ADC interrupt */
	NVIC_InitStructure.NVIC_IRQChannel = ADC1_2_IRQn;

	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);

}

static void cur_fbk_adc_init(void){
	
	ADC_DeInit(ADC1);
	ADC_InitTypeDef ADC_InitStructure;
	/* ADC1 configuration ------------------------------------------------------*/
	ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
	ADC_InitStructure.ADC_ScanConvMode = ENABLE;
	ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
	ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
	ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
	ADC_InitStructure.ADC_NbrOfChannel = 2;

	/* Set injected sequencer length */
	ADC_InjectedSequencerLengthConfig(ADC1, 2);
	/* ADC1 injected channel Configuration */ 
	ADC_InjectedChannelConfig(ADC1, ADC_Channel_0, 1, ADC_SampleTime_71Cycles5);
	ADC_InjectedChannelConfig(ADC1, ADC_Channel_1, 2, ADC_SampleTime_71Cycles5);
	//ADC_InjectedChannelConfig(ADC1, ADC_Channel_2, 1, ADC_SampleTime_71Cycles5);
	//ADC_InjectedChannelConfig(ADC1, ADC_Channel_3, 1, ADC_SampleTime_71Cycles5);	
	/* ADC1 injected external trigger configuration */
	//ADC_ExternalTrigInjectedConvConfig(ADC1, ADC_ExternalTrigInjecConv_T1_CC4);
	ADC_ExternalTrigInjectedConvConfig(ADC1, ADC_ExternalTrigInjecConv_None);

	//ADC_SetInjectedOffset(ADC1, ADC_InjectedChannel_1,2048);
	//ADC_SetInjectedOffset(ADC1, ADC_InjectedChannel_2,2048);
	
	/* Enable automatic injected conversion start after regular one */
	ADC_AutoInjectedConvCmd(ADC1, ENABLE);
	
	/* Enable ADC1 DMA */
	ADC_DMACmd(ADC1, ENABLE);
	
	/* Enable ADC1 external trigger */ 
	ADC_ExternalTrigConvCmd(ADC1, ENABLE);

	
	ADC_Init(ADC1, &ADC_InitStructure);
	ADC_Cmd(ADC1, ENABLE);
	
	ADC_ResetCalibration(ADC1);
	while(ADC_GetResetCalibrationStatus(ADC1)){
		/**
			TODO
            timeout_detect
		*/
		
	}
	ADC_StartCalibration(ADC1);
	while(ADC_GetCalibrationStatus(ADC1)){
		/**
			TODO
            timeout_detect
		*/
	}

	ADC_ITConfig(ADC1, ADC_IT_JEOC, ENABLE);
}

static void cur_fbk_rcc_init(void){

	/* ADCCLK = PCLK2/6 */
	RCC_ADCCLKConfig(RCC_PCLK2_Div6); 
	  
	/* Enable peripheral clocks ------------------------------------------------*/
	/* Enable DMA1 and DMA2 clocks */
	//RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1 | RCC_AHBPeriph_DMA2, ENABLE);

	/* Enable ADC1 and GPIOA clocks */
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_GPIOA, ENABLE);
}

static void cur_fbk_pin_init(void){

	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
	GPIO_Init(GPIOA, &GPIO_InitStructure);		
  
}

static uint16_t cur_fbk_get_ad_val(uint8_t channel){
	ADC_RegularChannelConfig(ADC1, channel, 1, ADC_SampleTime_239Cycles5 );
	ADC_SoftwareStartConvCmd(ADC1, ENABLE); //使能软件转换功能
	//等待转换结束
	/*
 		EOC:转换结束位 (End of conversion)
		该位由硬件在(规则或注入)通道组转换结束时设置,由软件清除或由读取ADC_DR时清除
		0:转换未完成;
		1:转换完成。 		
	 */
	while((ADC1->SR & ADC_FLAG_EOC) != ADC_FLAG_EOC){}
	//while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC )){}
	
	return ADC_GetConversionValue(ADC1); //返回最近一次 ADC1 规则组的转换结果
}
	
void cur_fbk_init(void){
	cur_fbk_rcc_init();
	cur_fbk_pin_init();
	cur_fbk_irq_init();
	cur_fbk_adc_init();
}

uint16_t cur_fbk_get_Ia_avl(uint8_t sample_times){
	uint32_t Ia_sum = 0;
	int8_t i;
	for(; i < sample_times; i++){
		Ia_sum+=cur_fbk_get_Ia();
	}
	return (uint16_t)(Ia_sum/sample_times);
}

uint16_t cur_fbk_get_Ib_avl(uint8_t sample_times){
	uint32_t Ib_sum = 0;
	int8_t i = 0;
	for(;i < sample_times; i++){
		Ib_sum+=cur_fbk_get_Ib();
	}
	return (uint16_t)(Ib_sum/sample_times);
}


uint16_t cur_fbk_get_Ia(void){
	return cur_fbk_get_ad_val(IA_CHANNEL_DRI);
}

uint16_t cur_fbk_get_Ib(void){
	return cur_fbk_get_ad_val(IB_CHANNEL_DRI);
}

int16_t cur_fbk_get_theta(void){
	return 0;
}

/******************************************************************************/
/*            STM32F10x Peripherals Interrupt Handlers                        */
/******************************************************************************/

/**
  * @brief  This function handles ADC1 and ADC2 global interrupts requests.
  * @param  None
  * @retval None
  */
void ADC1_2_IRQHandler(void)
{

	Ia_val = ADC_GetInjectedConversionValue(ADC1, ADC_InjectedChannel_1);
	Ib_val = ADC_GetInjectedConversionValue(ADC1, ADC_InjectedChannel_2);
	/* Clear ADC1 JEOC pending interrupt bit */
	ADC_ClearITPendingBit(ADC1, ADC_IT_JEOC);
}


uint16_t get_inject_ia(void){
	return Ia_val;
}

uint16_t get_inject_ib(void){
	return Ib_val;
}