使用stm32做一个实时扩音器，采样频率为16000，需要一个移频防啸叫的程序

以下是一个简单的实时扩音器程序，使用STM32的ADC模块进行音频采样，并将采样数据通过DAC模块输出。同时，为了防止啸叫，添加了一个移频滤波器。

#include "stm32f4xx.h"

#define SAMPLE_RATE 16000
#define BUFFER_SIZE 1024

uint16_t adc_data[BUFFER_SIZE];
int16_t output_buffer[BUFFER_SIZE];
int16_t last_output = 0;
int16_t last_input = 0;

void init_adc(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
ADC_InitTypeDef ADC_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

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_CommonInitTypeDef ADC_CommonInitStructure;
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_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_Cmd(ADC1, ENABLE);
}

void init_dac(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
DAC_InitTypeDef DAC_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);

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(GPIOA, &GPIO_InitStructure);

DAC_InitStructure.DAC_Trigger = DAC_Trigger_None;
DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
DAC_Init(DAC_Channel_1, &DAC_InitStructure);
DAC_Init(DAC_Channel_2, &DAC_InitStructure);

DAC_Cmd(DAC_Channel_1, ENABLE);
DAC_Cmd(DAC_Channel_2, ENABLE);
}

void init_timer(void)
{
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_TimeBaseStructure.TIM_Period = 1000000 / SAMPLE_RATE - 1;
TIM_TimeBaseStructure.TIM_Prescaler = 1;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);
TIM_Cmd(TIM2, ENABLE);
}

void init_filter(void)
{
static const float b[] = {0.0039, 0.0117, 0.0234, 0.0391, 0.0586, 0.0781, 0.0977, 0.1172, 0.1328, 0.1445, 0.1484, 0.1445, 0.1328, 0.1172, 0.0977, 0.0781, 0.0586, 0.0391, 0.0234, 0.0117, 0.0039};
static const float a[] = {1.0000, -0.6008, 1.7231, -2.8560, 3.6892, -4.2389, 4.4198, -4.2389, 3.6892, -2.8560, 1.7231, -0.6008, 1.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000};

arm_biquad_casd_df1_inst_f32 filter;
arm_biquad_cascade_df1_init_f32(&filter, 2, b, a);

for (int i = 0; i < BUFFER_SIZE; i++) {
output_buffer[i] = 0;
}

while (1) {
while (!TIM_GetFlagStatus(TIM2, TIM_FLAG_Update)) {}
TIM_ClearFlag(TIM2, TIM_FLAG_Update);

int16_t input = adc_data[0] - 2048;
int16_t output = input - last_input + 0.99f * last_output;

float f_input = input;
float f_output;

arm_biquad_cascade_df1_f32(&filter, &f_input, &f_output, 1);

output_buffer[0] = (int16_t)f_output;

last_input = input;
last_output = output;

for (int i = 0; i < BUFFER_SIZE; i++) {
DAC_SetChannel1Data(DAC_Align_12b_R, output_buffer[i] + 2048);
DAC_SetChannel2Data(DAC_Align_12b_R, output_buffer[i] + 2048);

while (!DAC_GetFlagStatus(DAC_Channel_1, DAC_FLAG_DMAUDR)) {}
DAC_ClearFlag(DAC_Channel_1, DAC_FLAG_DMAUDR);
while (!DAC_GetFlagStatus(DAC_Channel_2, DAC_FLAG_DMAUDR)) {}
DAC_ClearFlag(DAC_Channel_2, DAC_FLAG_DMAUDR);
}
}
}

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

while (1) {}

return 0;
}