DDS

-- DDS処理メモ --
割り込みのオーバヘッド割合が大きいため、サンプリング周波数を高くできない・・・

■仕様
MPU: ATtiny2313@24.576MHz
出力: 2CH PWM (MAX 4CH)
サンプリング周波数: 約125kHz
垂直分解能: 8bit
波形テーブル: 正弦波256サンプル

出力波形例

配線（ん）

以下参考ソース

/*
 * softwareDDS.c
 *
 * Created: 2016/03/05 18:59:42
 * Author : kingyoZAL1
 */ 

#include <avr/io.h>
#define F_CPU 24.576E6
#include <util/delay.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>

/* Global val */
volatile uint32_t acc1 = 0, acc2 = 0;
volatile uint32_t adder1, adder2;

/* (1 / 2^32) / (7.97526 * 10^-6) */
#define DDS_RES 0.0002919411

/* MPU初期化 */
static void InitMPU (void)
{
 DDRD = 0x01;
 PORTD = 0;
 
 /* デバッグ用 */
 DDRD |= 1 << 4;
}

/* PWM設定 */
static void InitPWM (void)
{
 /* Duty = 50% */
 OCR0A = 0x80;
 OCR0B = 0x80;
 
 /* OC0A, OC0B */
 DDRB |= 1 << 2;
 DDRD |= 1 << 5;
 TCCR0A = 0b10100011;
         // ||||||++--- WGM01, WGM00
         // ||||++----- Reserved(0)
         // ||++------- COM0B1, COM0B0
         // ++--------- COM0A1, COM0A0
 TCCR0B = 0b10000001;
         // |||||+++--- CS02, CS01, CS00
         // ||||+------ WGM02
         // ||++------- Reserved(0)
         // ++--------- FOC0A, FOC0B
#if 0
 /* OC1A, OC1B */
 DDRB |= 1 << 3;
 DDRB |= 1 << 4;
 TCCR1A = 0b10100001;
         // ||||||++--- WGM11, WGM10
         // ||||++----- Reserved(0)
         // ||++------- COM1B1, COM1B0
         // ++--------- COM1A1, COM1A0
 TCCR1B = 0b10001001;
         // |||||+++--- CS02, CS01, CS00
         // ||||+------ WGM12
         // |||+------- WGM13
         // ||+-------- Reserved(0)
         // ++--------- ICNC1, ICES1
#endif
}

/* 正弦波波形テーブル */
const uint8_t sinewave[] PROGMEM =
{
 0x80,0x83,0x86,0x89,0x8c,0x8f,0x92,0x95,0x98,0x9c,0x9f,0xa2,0xa5,0xa8,0xab,0xae,
 0xb0,0xb3,0xb6,0xb9,0xbc,0xbf,0xc1,0xc4,0xc7,0xc9,0xcc,0xce,0xd1,0xd3,0xd5,0xd8,
 0xda,0xdc,0xde,0xe0,0xe2,0xe4,0xe6,0xe8,0xea,0xec,0xed,0xef,0xf0,0xf2,0xf3,0xf5,
 0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfc,0xfc,0xfd,0xfe,0xfe,0xff,0xff,0xff,0xff,0xff,
 0xff,0xff,0xff,0xff,0xff,0xff,0xfe,0xfe,0xfd,0xfc,0xfc,0xfb,0xfa,0xf9,0xf8,0xf7,
 0xf6,0xf5,0xf3,0xf2,0xf0,0xef,0xed,0xec,0xea,0xe8,0xe6,0xe4,0xe2,0xe0,0xde,0xdc,
 0xda,0xd8,0xd5,0xd3,0xd1,0xce,0xcc,0xc9,0xc7,0xc4,0xc1,0xbf,0xbc,0xb9,0xb6,0xb3,
 0xb0,0xae,0xab,0xa8,0xa5,0xa2,0x9f,0x9c,0x98,0x95,0x92,0x8f,0x8c,0x89,0x86,0x83,
 0x80,0x7c,0x79,0x76,0x73,0x70,0x6d,0x6a,0x67,0x63,0x60,0x5d,0x5a,0x57,0x54,0x51,
 0x4f,0x4c,0x49,0x46,0x43,0x40,0x3e,0x3b,0x38,0x36,0x33,0x31,0x2e,0x2c,0x2a,0x27,
 0x25,0x23,0x21,0x1f,0x1d,0x1b,0x19,0x17,0x15,0x13,0x12,0x10,0x0f,0x0d,0x0c,0x0a,
 0x09,0x08,0x07,0x06,0x05,0x04,0x03,0x03,0x02,0x01,0x01,0x00,0x00,0x00,0x00,0x00,
 0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x01,0x02,0x03,0x03,0x04,0x05,0x06,0x07,0x08,
 0x09,0x0a,0x0c,0x0d,0x0f,0x10,0x12,0x13,0x15,0x17,0x19,0x1b,0x1d,0x1f,0x21,0x23,
 0x25,0x27,0x2a,0x2c,0x2e,0x31,0x33,0x36,0x38,0x3b,0x3e,0x40,0x43,0x46,0x49,0x4c,
 0x4f,0x51,0x54,0x57,0x5a,0x5d,0x60,0x63,0x67,0x6a,0x6d,0x70,0x73,0x76,0x79,0x7c,
};

/* DDS処理 */
ISR (TIMER1_COMPA_vect)
{
 acc1 += adder1;
 OCR0A = pgm_read_byte(&sinewave[acc1 >> 24]);
 acc2 += adder2;
 OCR0B = pgm_read_byte(&sinewave[acc2 >> 24]);
}

/* 周波数設定 */
static void setFrq (uint16_t af1, uint16_t af2)
{
 adder1 = af1 / DDS_RES;
 adder2 = af2 / DDS_RES;
}

/* MAIN */
int main (void)
{
 uint16_t f1, f2;

 InitMPU();
 InitPWM();
 
 /* 定周期DDS処理用タイマ1設定 */
 TCCR1A = 0b00000000;
 TCCR1B = 0b00001001;
 TIMSK = 0b01000000;
 OCR1A = 196 - 1; // 196 -> About 7.97526us
 
 sei ();
 
 f1 = 10000;
 f2 = 2000;
 setFrq(f1, f2);
 
 while (1) 
 {
  /* 波形観測用トリガ信号 */
  PORTD |= 1 << 4;
  PORTD &= ~(1 << 4);
  
  /* 周波数切替てすと */
  setFrq(2000, 5000);
  _delay_ms(2);
  
  setFrq(10000, 2000);
  _delay_ms(2);
 }
}

Let's キモい波形生成！

～　おわり　～