/*-------------------------------------------------------------*-
File name: rhythmeheart.c
Author:Yorkchang   Version:1.00   Date:3.20,06
Description:本模塊為心率計算模塊。
Function List:
1.unsigned char rhythmcount(unsigned char *fifo) 心率計算函數
History:
 <author>      <time>       <version >     <desc>
 Yorkchang     3.20          1.0                 參照網上資料提供的算法編程

-----------------------------------------------------------------
心率計算模塊
-*--------------------------------------------------------------*/
#include "main.h"
#include "rhythmeheart.h"

/*************************************************
  Function:   rhythmcount
  Description:計算心率值
  Calls:      --
  Called By:  real_sample()
  函數入口：數據區首地址
  Return:     rhythm 心率值
*************************************************/

unsigned char rhythmcount(unsigned char *fifo)
{
	signed char i;
	signed char diff[max_data];             //求導數數據區
	signed char dif_max=0;                  //導數最大值
	signed char thr_max;                    //閾值最大值
	unsigned char j=0;
	signed char k[8];                       //最大值數組
	unsigned char rhythm;
	float DR_R;                             //R-R間距
	
	*diff=0;                                //數據區首兩個數據導數置0
	*(diff+1)=0;
	for(i=2;i<max_data-2;i++)               //按DIFF(i)=f(i+1)-f(i-1)+2*f(i+2)-2*f(i-2)公式計算導數
	{
		*(diff+i)=(signed char)(*(fifo+i+1))+2*(signed char)(*(fifo+i+2))-(signed char)(*(fifo+i-1))-2*(signed char)(*(fifo+i-2));
	}
	*(diff+max_data-1)=0;                   //數據區末兩個數據導數置0
	*(diff+max_data)=0;
	for(i=0;i<max_data;i++)                 //求導數最大值
	{
		if((dif_max)>*(diff+i))
		dif_max=*(diff+i);
	} 
	thr_max=(dif_max>>1)-(dif_max>>3);       //設定閾值，為導數最大值的0.375倍
	for(i=1;i<max_data-1;i++)                //將滿足f(i)>thr_max和f(i)*f(i+1)<0這兩個條件的值找到,即為R波最高點
	{
		if((*(diff+i)>thr_max)&&(((*(diff+i))^(*(diff+i+1)))>>7))
		k[j++]=i;
	}
	DR_R=(k[j-1]-k[0])/(j-1);                //計算R-R間距
	rhythm=(unsigned char)(12000/DR_R);      //通過公式200*60/DR-R求得心率值
	return rhythm;
}
	
/*-----------------------------------------------------------------*-
  --------------------END OF FILE------------------------------------
 -*-----------------------------------------------------------------*/