【炒冷饭】STM32实现IIR滤波器，可用matlab生成的头文件

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reporter发表于 2013-9-4 11:04 | 只看该作者

【炒冷饭】STM32实现IIR滤波器，可用matlab生成的头文件

matlab, 滤波器

本帖最后由 monkeynav 于 2013-8-21 18:09 编辑

原帖刊载于ourdev：http://www.amobbs.com/thread-4165021-1-1.html
原帖代码搞错，也无法编辑，很多人又找不到后面的更正，为了不误导更多人，就在这里重新发一遍。

这里提供用于AVR和STM32的IIR滤波器代码下载，保证可用，不需要额外修改：

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放假实在无聊，即将到来的高三非常恐怖，先偷闲一把。

matlab的fdatool是好东西，不过很多人不知道该怎么使用它生成的C头文件。

该程序已经用于心电采集实验

不多说，切入正题

这里有个fdatool设计的IIR高通滤波器，采样率400Hz时截止频率1Hz。
设计定型之后，要做些调整。

以下说明中的英文名词有些可能对不上fdatool界面上的原文，请大家意会吧

第一步：
点击菜单中的Edit-&gt;Convert Structure 选择Direct Form I ，SOS，（必须是Direct Form I，&nbsp;&nbsp;II不行）
一般情况下，按照默认设置，fdatool设计都是由二阶部分串联组成的。
这种结构的滤波器稳定性比一个section的要好很多，其他方面的性能也好些。
如果不是的话，点击Convert to second order sections。
这时，滤波器的结构（structure）应该显示为 Direct Form I，second order sections

第二步：
选择quantize filter，精度选择single precision floating point （单精度浮点）
之所以不用定点是因为噪声太大，也不容易稳定。
点击菜单中的Targets -&gt; generate c header ，选择export as：single precision floating point （单精度浮点）
填写变量名称时，把NUM改成IIR_B，DEN改成IIR_A,其他不用动，保存为iir_coefs.h

保存好的文件如下：
//一大堆注释
//然后：
/* General type conversion for MATLAB generated C-code&nbsp;&nbsp;*/
#include &quot;tmwtypes.h&quot;
/*
* Expected path to tmwtypes.h
* C:\Program Files\MATLAB\R2010a\extern\include\tmwtypes.h
*/
/*
* Warning - Filter coefficients were truncated to fit specified data type.&nbsp;&nbsp;
*&nbsp; &nbsp;The resulting response may not match generated theoretical response.
*&nbsp; &nbsp;Use the Filter Design &amp; Analysis Tool to design accurate
*&nbsp; &nbsp;single-precision filter coefficients.
*/
#define MWSPT_NSEC 9
const int NL[MWSPT_NSEC] = { 1,3,1,3,1,3,1,3,1 };
const real32_T IIR_B[MWSPT_NSEC][3] = {
{
&nbsp; &nbsp;&nbsp;&nbsp;0.8641357422,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; -2,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp;&nbsp;0.9949035645,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;-1.999938965,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp;&nbsp;0.9985351563,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp; -1.99987793,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
{
&nbsp; &nbsp;&nbsp;&nbsp;0.9996337891,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;1,&nbsp; &nbsp; -1.99987793,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;}
};
const int DL[MWSPT_NSEC] = { 1,3,1,3,1,3,1,3,1 };
const real32_T IIR_A[MWSPT_NSEC][3] = {
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;-1.938049316,&nbsp; &nbsp;0.9401855469
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;-1.989501953,&nbsp; &nbsp;0.9900512695
&nbsp;&nbsp;},
{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;-1.996887207,&nbsp; &nbsp;0.9971923828
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;-1.999084473,&nbsp; &nbsp;0.9993286133
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;}
};

第三步：
打开iir_coefs.h把MWSPT_NSEC替换成IIR_NSEC,
NL、DL数组删除掉，real32_T改成float ，
其中有一个#include &quot;twmtypes.h&quot;,不要它了，删掉
改完的文件如下：

#define IIR_NSEC 9
&nbsp;&nbsp;//原来叫做MWSPT_NSEC

const float IIR_B[IIR_NSEC][3] = {
&nbsp;&nbsp;//为什么改为float很明显了吧
&nbsp;&nbsp;{
&nbsp; &nbsp; 0.8641357422,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;-2,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp; 0.9949035645,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp;&nbsp;-1.999938965,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
{
&nbsp; &nbsp; 0.9985351563,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp; -1.99987793,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;0.9996337891,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp; -1.99987793,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;1
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;}
};
const float IIR_A[IIR_NSEC][3] = {
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp;&nbsp;-1.938049316,&nbsp;&nbsp;0.9401855469
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp;&nbsp;-1.989501953,&nbsp;&nbsp;0.9900512695
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp;&nbsp;-1.996887207,&nbsp;&nbsp;0.9971923828
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp;&nbsp;-1.999084473,&nbsp;&nbsp;0.9993286133
&nbsp;&nbsp;},
&nbsp;&nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 1,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;0
&nbsp;&nbsp;}
};

保存文件，然后使用以下代码进行滤波
这段代码是根据Direct Form I 2阶IIR滤波的差分方程编写的
a0*y[n] = b0*x[n] + b1*x[n-1] + b2*x[n-2] - a1*y[n-1] -a2*y[n-2];

#include &quot;../platform.h&quot;
//#include &quot;iir_coefs.float.flat.h&quot;
//#include &quot;iir_coefs.float.sharp.h&quot;
#include &quot;iir_coefs_pass@2Hz_stop@0.8Hz.h&quot;
#include &quot;iir_filter.h&quot;
static float y[IIR_NSEC][3];
static float x[IIR_NSEC+1][3];
//IIR_NSEC阶直接型II IIR滤波器
//IIR_NSEC个二阶biquad串联
int16 iir_filter(int16 in)
{
&nbsp; &nbsp;&nbsp; &nbsp;uint16 i;
&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;x[0][0] = in;
&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;for(i=0;i&lt;IIR_NSEC;i++)
&nbsp; &nbsp;&nbsp; &nbsp;{
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;y[0] = x[0]*IIR_B[0] +x[1]*IIR_B[1] +x[2]*IIR_B[2]-y[1]*IIR_A[1]-y[2]*IIR_A[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; y[0] = 0;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; if(IIR_B[0] == 1) y[0]+=x[0];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[0] == -1) y[0]-=x[0];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[0] == -2) y[0]=y[0]-x[0]-x[0];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[0] == 0);&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else y[0] += x[0]*IIR_B[0];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; if(IIR_B[1] == 1) y[0]+=x[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[1] == -1) y[0]-=x[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[1] == -2) y[0]=y[0]-x[1]-x[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[1] == 0);&nbsp;&nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else y[0] += x[1]*IIR_B[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; if(IIR_B[2] == 1) y[0]+=x[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[2] == -1) y[0]-=x[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[2] == -2) y[0]=y[0]-x[2]-x[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_B[2] == 0);
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else y[0] += x[2]*IIR_B[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; if(IIR_A[1] == 1) y[0]-=y[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_A[1] == -1) y[0]+=y[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_A[1] == -2) y[0]=y[0]+y[1]+y[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_A[1] == 0);
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else y[0] -= y[1]*IIR_A[1];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; if(IIR_A[2] == 1) y[0]-=y[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_A[2] == -1) y[0]+=y[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_A[2] == -2) y[0]=y[0]+y[2]+y[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else if(IIR_A[2] == 0);
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; else y[0] -= y[2]*IIR_A[2];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; if(IIR_A[0] != 1) y[0] /= IIR_A[0];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; y[2]=y[1];y[1]=y[0];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; x[2]=x[1];x[1]=x[0];
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; x[i+1][0] = y[0];
&nbsp; &nbsp;&nbsp; &nbsp;}
&nbsp; &nbsp;&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;if( x[IIR_NSEC][0]&gt;32767)&nbsp;&nbsp;x[IIR_NSEC][0]=32767;
&nbsp; &nbsp;&nbsp; &nbsp;if( x[IIR_NSEC][0]&lt;-32768) x[IIR_NSEC][0]=-32768;
&nbsp; &nbsp;&nbsp; &nbsp;return&nbsp;&nbsp;((int16)x[IIR_NSEC][0]);&nbsp; &nbsp;
&nbsp; &nbsp;&nbsp; &nbsp;
}
//复位滤波器
void iir_reset(void)
{
&nbsp; &nbsp; uint16 i,j;
&nbsp; &nbsp;
&nbsp; &nbsp; for(i=0;i&lt;IIR_NSEC+1;i++)
&nbsp; &nbsp; {
&nbsp; &nbsp;&nbsp; &nbsp; for(j=0;j&lt;3;j++)
&nbsp; &nbsp;&nbsp; &nbsp; {
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; x[j]=0;
&nbsp; &nbsp;&nbsp; &nbsp; }
&nbsp; &nbsp; }
&nbsp; &nbsp;
&nbsp; &nbsp; for(i=0;i&lt;IIR_NSEC;i++)
&nbsp; &nbsp; {
&nbsp; &nbsp;&nbsp; &nbsp; for(j=0;j&lt;3;j++)
&nbsp; &nbsp;&nbsp; &nbsp; {
&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; y[j]=0;
&nbsp; &nbsp;&nbsp; &nbsp; }
&nbsp; &nbsp; }
}

//iir_filter.h
#ifndef _IIR_FILTER_H__
#define _IIR_FILTER_H__
int16 iir_filter(int16 x);
void iir_reset(void);
#endif

使用方法:
首先写好iir_coefs.h，然后调用iir_filter.c对数据流进行滤波
一个伪代码例子：
while(运行中)
{
保存到SD卡(iir_filter(读取ADC采样值()));
}

这个函数比STM32 DSP库中的函数要好很多，DSP库中的2个IIR滤波函数都不能连续处理数据流。
记得在开始滤波之前重置滤波器
iir_reset();

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