请教定时中断问题

只看该作者 · 2013-4-9 22:12

新手我想要个三相正弦信号，就用了查表法，400Hz，512个数据，也就是接近5us发送一次给DAC。用CTC模式。程序如下：
#include<avr/io.h>
#include<avr/interrupt.h>
long int i;
int a,b,c;
int s[]={0x80,0x82,0x83,0x85,0x86,0x88,0x89,0x8B,0x8D,0x8E,
0x90,0x91,0x93,0x94,0x96,0x97,0x99,0x9B,0x9C,0x9E,
0x9F,0xA1,0xA2,0xA4,0xA5,0xA7,0xA8,0xAA,0xAB,0xAD,
0xAE,0xB0,0xB1,0xB2,0xB4,0xB5,0xB7,0xB8,0xBA,0xBB,
0xBC,0xBE,0xBF,0xC0,0xC2,0xC3,0xC4,0xC6,0xC7,0xC8,
0xCA,0xCB,0xCC,0xCE,0xCF,0xD0,0xD1,0xD2,0xD4,0xD5,
0xD6,0xD7,0xD8,0xD9,0xDB,0xDC,0xDD,0xDE,0xDF,0xE0,
0xE1,0xE2,0xE3,0xE4,0xE5,0xE6,0xE7,0xE8,0xE9,0xEA,
0xEA,0xEB,0xEC,0xED,0xEE,0xEF,0xEF,0xF0,0xF1,0xF2,
0xF2,0xF3,0xF4,0xF4,0xF5,0xF6,0xF6,0xF7,0xF7,0xF8,
0xF9,0xF9,0xFA,0xFA,0xFA,0xFB,0xFB,0xFC,0xFC,0xFD,
0xFD,0xFD,0xFE,0xFE,0xFE,0xFE,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFE,0xFE,0xFE,0xFE,0xFD,0xFD,0xFD,0xFC,0xFC,
0xFB,0xFB,0xFA,0xFA,0xFA,0xF9,0xF9,0xF8,0xF7,0xF7,
0xF6,0xF6,0xF5,0xF4,0xF4,0xF3,0xF2,0xF2,0xF1,0xF0,
0xEF,0xEF,0xEE,0xED,0xEC,0xEB,0xEA,0xEA,0xE9,0xE8,
0xE7,0xE6,0xE5,0xE4,0xE3,0xE2,0xE1,0xE0,0xDF,0xDE,
0xDD,0xDC,0xDB,0xD9,0xD8,0xD7,0xD6,0xD5,0xD4,0xD2,
0xD1,0xD0,0xCF,0xCE,0xCC,0xCB,0xCA,0xC8,0xC7,0xC6,
0xC4,0xC3,0xC2,0xC0,0xBF,0xBE,0xBC,0xBB,0xBA,0xB8,
0xB7,0xB5,0xB4,0xB2,0xB1,0xB0,0xAE,0xAD,0xAB,0xAA,
0xA8,0xA7,0xA5,0xA4,0xA2,0xA1,0x9F,0x9E,0x9C,0x9B,
0x99,0x97,0x96,0x94,0x93,0x91,0x90,0x8E,0x8D,0x8B,
0x89,0x88,0x86,0x85,0x83,0x82,0x80,0x7E,0x7D,0x7B,
0x7A,0x78,0x77,0x75,0x73,0x72,0x70,0x6F,0x6D,0x6C,
0x6A,0x69,0x67,0x66,0x64,0x62,0x61,0x5F,0x5E,0x5C,
0x5B,0x59,0x58,0x56,0x55,0x53,0x52,0x50,0x4F,0x4E,
0x4C,0x4B,0x49,0x48,0x46,0x45,0x44,0x42,0x41,0x40,
0x3E,0x3D,0x3C,0x3A,0x39,0x38,0x36,0x35,0x34,0x33,
0x31,0x30,0x2F,0x2E,0x2C,0x2B,0x2A,0x29,0x28,0x27,
0x26,0x24,0x23,0x22,0x21,0x20,0x1F,0x1E,0x1D,0x1C,
0x1B,0x1A,0x19,0x18,0x17,0x16,0x16,0x15,0x14,0x13,
0x12,0x11,0x11,0x10,0x0F,0x0E,0x0E,0x0D,0x0C,0x0C,
0x0B,0x0A,0x0A,0x09,0x09,0x08,0x07,0x07,0x06,0x06,
0x06,0x05,0x05,0x04,0x04,0x03,0x03,0x03,0x02,0x02,
0x02,0x02,0x01,0x01,0x01,0x01,0x01,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x01,0x01,0x01,0x01,0x01,0x02,0x02,0x02,
0x02,0x03,0x03,0x03,0x04,0x04,0x05,0x05,0x06,0x06,
0x06,0x07,0x07,0x08,0x09,0x09,0x0A,0x0A,0x0B,0x0c,
0x0C,0x0D,0x0E,0x0E,0x0F,0x10,0x11,0x11,0x12,0x13,
0x14,0x15,0x16,0x16,0x17,0x18,0x19,0x1A,0x1B,0x1C,
0x1D,0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x27,
0x28,0x29,0x2A,0x2B,0x2C,0x2E,0x2F,0x30,0x31,0x32,
0x34,0x35,0x36,0x38,0x39,0x3A,0x3C,0x3D,0x3E,0x40,
0x41,0x42,0x44,0x45,0x46,0x48,0x49,0x4B,0x4C,0x4E,
0x4F,0x50,0x52,0x53,0x55,0x56,0x58,0x59,0x5B,0x5C,
0x5E,0x5F,0x61,0x62,0x64,0x65,0x67,0x69,0x6A,0x6C,
0x6D,0x6F,0x70,0x72,0x73,0x75,0x77,0x78,0x7A,0x7B,
0x7D,0x7E
};
void main()
{initdevices();
/*a=0;
b=0;
c=0;
i=0;*/
while(1)
{/*a=s[i];
b=s[(i+170)%512];
c=s[(i+340)%512];
if(i==512) i=0*/;}
}
void initport()
{DDRA=0xff;
DDRB=0xff;
DDRC=0xff;
DDRD=0xFF;
PORTD=0xff;
PORTA=0xFF;
PORTB=0xFF;
PORTC=0xFF;
}
void inittime0()
{TCCR0=0x00;
TCNT0=0x00;
OCR0=39;
TIMSK=0x02;
TCCR0=0x09;
}
void initdevices()
{//CLI();
initport();
inittime0();
sei();
}
ISR(TIMER0_COMP_vect)
{PORTB=s[i];
PORTA=s[(i+170)%512];
PORTC=s[(i+340)%512];
i++;
if(i==512) i=0;
}
问题：
正弦信号是有了，但是频率不对。分析的时候觉着应该是进出中断包括子程序时间都太长了，5us的时间根本应付不过来，输出的频率天壤之别啊。是不是这种方法只适合很少的查表数据。