如下程序是我从网上找来的一个例子，是否用如下公式算出来的？其中π这个数是取PI吗？
200个点的正弦表就是峰值为400的标准正弦表，其数组内的spwm[x]的计算公式是400-sin(π*x/200)*400。
#include<iom8v.h>
#include<macros.h>
#define uchar unsigned char
unsigned short spwm[200]={ 400,399,399,398,397,396,394,393,391,389,
387,385,382,380,377,374,371,367,364,360,
356,352,348,344,339,335,330,325,320,315,
310,304,299,294,291,285,279,274,268,262,
256,250,247,241,231,228,222,216,209,203,
201,200,199,199,198,198,197,196,194,193,
191,189,187,185,182,180,177,174,170,167,
164,160,156,152,148,144,139,135,130,125,
120,115,110,104, 99, 94, 88, 82, 76, 71,
65, 59, 53, 47, 41, 34, 28, 22, 16, 9,
3, 1, 6, 13, 19, 25, 31, 37, 44, 50,
56, 62, 68, 74, 79, 85, 91, 96,102,107,
112,118,123,127,132,137,141,146,150,154,
158,162,165,169,172,175,178,181,184,186,
188,190,192,194,195,196,197,198,199,199,
200,200,206,213,219,225,231,237,244,250,
256,262,268,274,279,285,291,296,302,307,
312,318,323,328,332,337,341,346,350,354,
358,362,365,369,372,375,378,381,384,386,
388,390,392,394,395,396,397,398,399,400};
/*{201,212,225,237,250,262,274,285,296,307,318,327,337,346,354,//带直流分量的正弦波
362,369,375,381,386,390,394,396,398,400,398,396,
394,390,386,381,375,369,362,354,346,337,327,318,307,296,285,
274,262,250,237,225,212,201,187,175,163,150,138,126,115,104,
93,82,73,63,54,46,38,31,25,19,14,10,6,4,2,0,0,0,0,0,2,4,6,10,
14,19,25,31,38,46,54,63,73,82,93,104,115,126,138,150,163,175,187};*/
unsigned int k=0;
//****************系统初始化***************************
void timer1_init(void)
{
TCCR1B=0x00; //清零
TCNT1=0x0000; //计数器赋初值
OCR1A=0xc8; //A路比较值（***OCR1A/OCR1B中的值不得超过ICR1的值***）
ICR1=0x0190; //400,即8khz
//改变频率-ICR1(反比)
TCCR1A=0xA2;
TCCR1B=0x13 ; //无预分频 8分频
}
//---------------------------------------------------
//*****************主程序*********************************
//---------------------------------------------------------
#pragma interrupt_handler timer1_ovf_isr:7
#pragma interrupt_handler timer1_ovf_isr:8
/*---------------------------------------------------------*/
//***********定时器T1中断程序***************************
/*---------------------------------------------------------*/
uchar i=0;
void timer1_ovf_isr(void)
{
OCR1A=spwm[i++]; //重新赋初值
if(i>=200)
{
i=0;
}
}
void main(void)
{
unsigned int top=0x0190;//////0x258;0x002c;0x0050;
DDRB=0xFF;
PORTB=0xff;
timer1_init(); //初始化定时器T1
TIMSK=0x18; //开比较中断
SEI(); //开全局中断
OCR1A=0;
while (1)
{
}
} |
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