给我一个stm32的同步滤波器的keil代码

抱歉，我是一名AI语言模型，无法直接为您提供代码。但是，以下是一个基本的STM32同步滤波器的代码框架，您可以根据您的需求进行修改和优化：

#include "stm32f4xx.h"

#define SAMPLE_RATE 20000 //采样率
#define CUTOFF_FREQ 5000 //截止频率

volatile uint16_t adc_value; //ADC采样值
volatile float filter_output; //滤波器输出

float coeff_a[2], coeff_b[2]; //滤波器系数

void init_adc(void)
{
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
  
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    ADC_InitTypeDef ADC_InitStructure;
    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_Cmd(ADC1, ENABLE);
}

void init_filter(void)
{
    float RC = 1.0/(2*M_PI*CUTOFF_FREQ);
    float dt = 1.0/SAMPLE_RATE;

    coeff_b[0] = RC/(RC+dt);
    coeff_b[1] = coeff_b[0];
    coeff_a[0] = (RC-dt)/(RC+dt);
    coeff_a[1] = -1*coeff_a[0];
}

float filter(float input)
{
    static float prev_input[2], prev_output[2];

    prev_input[1] = prev_input[0];
    prev_input[0] = input;
    prev_output[1] = prev_output[0];

    float output = coeff_b[0]*prev_input[0] + coeff_b[1]*prev_input[1] - coeff_a[0]*prev_output[0] - coeff_a[1]*prev_output[1];

    prev_output[0] = output;

    return output;
}

int main(void)
{
    init_adc();
    init_filter();

    while(1)
    {
        ADC_SoftwareStartConv(ADC1);
        while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
        adc_value = ADC_GetConversionValue(ADC1);

        float input = (float)adc_value/4095*3.3; //将ADC采样值转换为电压值
        filter_output = filter(input);
    }
}