stm32adc测频率

在STM32中，可以使用定时器模块来测量频率。首先，使用ADC模块采集输入信号，然后将采样值送入定时器模块进行计数，最后利用计数值和采样时间计算频率。下面是一个简单的测量频率的代码示例：

#include "stm32f4xx.h"
#include <stdio.h>

float frequency = 0.0f;
uint32_t counter = 0;

void TIM3_IRQHandler(void)
{
    if(TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET) {
        TIM_ClearITPendingBit(TIM3, TIM_IT_Update);
        frequency = (float)counter / 0.001f;  // 采样时间为1ms
        counter = 0;  // 计数器清零
    }
}

void ADC_IRQHandler(void)
{
    if(ADC_GetITStatus(ADC1, ADC_IT_EOC) != RESET) {
        ADC_ClearITPendingBit(ADC1, ADC_IT_EOC);
        counter++;
    }
}

int main(void)
{
    // 初始化ADC模块
    ADC_InitTypeDef ADC_InitStructure;
    ADC_CommonInitTypeDef ADC_CommonInitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
    ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
    ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
    ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
    ADC_Init(ADC1, &ADC_InitStructure);
    ADC_CommonInit(&ADC_CommonInitStructure);
    ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
    ADC_InitStructure.ADC_ScanConvMode = DISABLE;
    ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
    ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_InitStructure.ADC_NbrOfConversion = 1;
    ADC_Init(ADC1, &ADC_InitStructure);
    ADC_ITConfig(ADC1, ADC_IT_EOC, ENABLE);
    ADC_Cmd(ADC1, ENABLE);

    // 初始化定时器模块
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
    TIM_TimeBaseStructure.TIM_Period = 999;
    TIM_TimeBaseStructure.TIM_Prescaler = 83;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
    TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);
    TIM_Cmd(TIM3, ENABLE);

    // 中断优先级配置
    NVIC_InitTypeDef NVIC_InitStructure;
    NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    NVIC_InitStructure.NVIC_IRQChannel = ADC_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    while(1) {
        // 等待频率计算完成
        if(frequency != 0.0f) {
            printf("Frequency: %.2f Hz\n", frequency);
            frequency = 0.0f;
        }
    }
}

在这个例子中，我们使用TIM3定时器模块和ADC1模块来测量频率。首先，我们初始化ADC模块，并将采样引脚PA1配置为模拟输入模式。然后，我们初始化TIM3定时器模块，并将计数时间设置为1ms。在定时器中断服务函数中，我们清除定时器中断标志，并计算频率值。在ADC中断服务函数中，我们每次采样到一个值就将计数器加1。最后，在主循环中等待计算完成，并将计算结果输出到串口。