没有函数信号发生器，做了个简单的delta-sigma正弦波发生器

#define F_CPU 9600000UL // 9.6 MHz

#include <util/delay.h>

#include <avr/io.h>

#include <avr/interrupt.h> 

#include <avr/pgmspace.h>

#define PWM_PRESCALE 110

#define SAMPLE_RATE ((9600000/PWM_PRESCALE))

#define DDS_ACCU_MAX 0x10000



unsigned char DDS_value;

unsigned int dds_diff;

unsigned int cycle_counter;

unsigned char phase;

unsigned int dds_accu;

unsigned char dds_count;

unsigned char PORT_buf;



const unsigned char sin_tbl [] PROGMEM = {

0x7f, 0x82, 0x85, 0x88, 0x8b, 0x8f, 0x92, 0x95,

0x98, 0x9b, 0x9e, 0xa1, 0xa4, 0xa7, 0xaa, 0xad,

0xb0, 0xb2, 0xb5, 0xb8, 0xbb, 0xbe, 0xc0, 0xc3,

0xc6, 0xc8, 0xcb, 0xcd, 0xd0, 0xd2, 0xd4, 0xd7,

0xd9, 0xdb, 0xdd, 0xdf, 0xe1, 0xe3, 0xe5, 0xe7,

0xe9, 0xea, 0xec, 0xee, 0xef, 0xf0, 0xf2, 0xf3,

0xf4, 0xf5, 0xf7, 0xf8, 0xf9, 0xf9, 0xfa, 0xfb,

0xfc, 0xfc, 0xfd, 0xfd, 0xfd, 0xfe, 0xfe, 0xfe,

0xfe, 0xfe, 0xfe, 0xfe, 0xfd, 0xfd, 0xfd, 0xfc,

0xfc, 0xfb, 0xfa, 0xf9, 0xf9, 0xf8, 0xf7, 0xf5,

0xf4, 0xf3, 0xf2, 0xf0, 0xef, 0xee, 0xec, 0xea,

0xe9, 0xe7, 0xe5, 0xe3, 0xe1, 0xdf, 0xdd, 0xdb,

0xd9, 0xd7, 0xd4, 0xd2, 0xd0, 0xcd, 0xcb, 0xc8,

0xc6, 0xc3, 0xc0, 0xbe, 0xbb, 0xb8, 0xb5, 0xb2,

0xb0, 0xad, 0xaa, 0xa7, 0xa4, 0xa1, 0x9e, 0x9b,

0x98, 0x95, 0x92, 0x8f, 0x8b, 0x88, 0x85, 0x82,

0x7f, 0x7c, 0x79, 0x76, 0x73, 0x6f, 0x6c, 0x69,

0x66, 0x63, 0x60, 0x5d, 0x5a, 0x57, 0x54, 0x51,

0x4e, 0x4c, 0x49, 0x46, 0x43, 0x40, 0x3e, 0x3b,

0x38, 0x36, 0x33, 0x31, 0x2e, 0x2c, 0x2a, 0x27,

0x25, 0x23, 0x21, 0x1f, 0x1d, 0x1b, 0x19, 0x17,

0x15, 0x14, 0x12, 0x10, 0x0f, 0x0e, 0x0c, 0x0b,

0x0a, 0x09, 0x07, 0x06, 0x05, 0x05, 0x04, 0x03,

0x02, 0x02, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00,

0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x02,

0x02, 0x03, 0x04, 0x05, 0x05, 0x06, 0x07, 0x09,

0x0a, 0x0b, 0x0c, 0x0e, 0x0f, 0x10, 0x12, 0x14,

0x15, 0x17, 0x19, 0x1b, 0x1d, 0x1f, 0x21, 0x23,

0x25, 0x27, 0x2a, 0x2c, 0x2e, 0x31, 0x33, 0x36,

0x38, 0x3b, 0x3e, 0x40, 0x43, 0x46, 0x49, 0x4c,

0x4e, 0x51, 0x54, 0x57, 0x5a, 0x5d, 0x60, 0x63,

0x66, 0x69, 0x6c, 0x6f, 0x73, 0x76, 0x79, 0x7c

};

unsigned char digital_signal_input=192;

int accumulator,accumulator1,accumulator2;

unsigned char ddc;

unsigned char portb_buff;



ISR(TIM0_COMPA_vect){

        PORTB=portb_buff;



// 1order

        if (accumulator>=0x80){

                portb_buff|=(1<<PB2);

                ddc=0xff;

        }else{

                portb_buff&=~(1<<PB2);

                ddc=0x00;

        }

        accumulator=digital_signal_input-ddc+accumulator;



        phase = dds_accu>> 8; /* phase = DDS accumlator upper byte */

        digital_signal_input = pgm_read_byte (& sin_tbl [phase]); /* output value get from sin table */

        dds_accu += dds_diff;



}



int main(void){

        DDRB|=(1<<PB2);

        

        TCCR0A=(0b10<<WGM00); //CTC mode

        TCCR0B=(0b001<<CS00); //div by 1

        OCR0A=(PWM_PRESCALE-1); //

        TIMSK0=(1<<OCIE0A);

        dds_diff = DDS_ACCU_MAX * 1000 / SAMPLE_RATE; // set phase step in each sample         

        sei();

        portb_buff=PORTB;



        while(1){

        };

}