一、功能概述

本示例实现两个滤波器：

中值滤波器（Median Filter）：对短期异常值（如尖峰噪声）有良好的抑制能力；
低通滤波器（Low-Pass Filter）：对数据进行平滑处理，适合去除高频抖动。

适用于如 ADC传感器数据处理、电子秤、电流电压读取等场景。

二、代码结构说明

✅ 头文件 `filter.h`

#ifndef FILTER_H
#define FILTER_H#define WINDOW_SIZE 50typedef struct {int buffer[WINDOW_SIZE]; // 数据缓冲区int index;               // 当前写入索引（环形）int count;               // 当前已存数据个数
} MedianFilter;extern MedianFilter myMedianFilter;void medianInit(MedianFilter* filter);
int  medianFilter(MedianFilter* filter, int new_value);
int  lowPassFilter(int input);#endif

✅ 源文件 `filter.c`

🔹 中值滤波器实现

#include "filter.h"
#include <stdlib.h>// 冒泡排序用于求中值（可替换为更高效算法）
static void sort_array(int* src, int* dst, int size) {for (int i = 0; i < size; i++) dst[i] = src[i];for (int i = 0; i < size - 1; i++) {for (int j = i + 1; j < size; j++) {if (dst[i] > dst[j]) {int temp = dst[i];dst[i] = dst[j];dst[j] = temp;}}}
}// 初始化滤波器状态
void medianInit(MedianFilter* filter) {for (int i = 0; i < WINDOW_SIZE; i++)filter->buffer[i] = 0;filter->index = 0;filter->count = 0;
}// 中值滤波主函数
int medianFilter(MedianFilter* filter, int new_value) {filter->buffer[filter->index] = new_value;filter->index = (filter->index + 1) % WINDOW_SIZE;if (filter->count < WINDOW_SIZE)filter->count++;int sorted[WINDOW_SIZE];sort_array(filter->buffer, sorted, filter->count);if (filter->count % 2 == 1)return sorted[filter->count / 2];elsereturn (sorted[filter->count / 2 - 1] + sorted[filter->count / 2]) / 2;
}

🔹 低通滤波器实现

int lowPassFilter(int input) {static int prev_output = 0;uint8_t alpha_shift = 3;  // α = 1/8，越大越平滑prev_output = prev_output + ((input - prev_output) >> alpha_shift);return prev_output;
}

✅ 主函数测试示例

#include <stdio.h>
#include "filter.h"MedianFilter myMedianFilter;int mainTest() {medianInit(&myMedianFilter);int data[] = {100, 102, 98, 500, 101, 99, 97, 103};int len = sizeof(data) / sizeof(data[0]);for (int i = 0; i < len; i++) {int medFiltered = medianFilter(&myMedianFilter, data[i]);int lpFiltered = lowPassFilter(data[i]);printf("Raw: %d\tMedian: %d\tLowPass: %d\n", data[i], medFiltered, lpFiltered);}return 0;
}