demo_8_6.i

基于比较匹配输出的脉冲宽度调制PWM,利用ATMEGA16的T/C0匹配输出脚OC0上的PWM波通过RC积分电路,滤掉高频进行平滑后,得到模拟的正弦波信号.

/*********************************************
File name			: demo_8_6.c
Chip type           : ATmega16
Program type        : Application
Clock frequency     : 4.000000 MHz
Memory model        : Small
External SRAM size  : 0
Data Stack size     : 256
*********************************************/

// CodeVisionAVR C Compiler
// (C) 1998-2001 Pavel Haiduc, HP InfoTech S.R.L.

// I/O registers definitions for the ATmega16


#pragma used+
sfrb TWBR=0;
sfrb TWSR=1;
sfrb TWAR=2;
sfrb TWDR=3;
sfrb ADCL=4;
sfrb ADCH=5;
sfrw ADCW=4;      // 16 bit access
sfrb ADCSRA=6;
sfrb ADMUX=7;
sfrb ACSR=8;
sfrb UBRRL=9;
sfrb UCSRB=0xa;
sfrb UCSRA=0xb;
sfrb UDR=0xc;
sfrb SPCR=0xd;
sfrb SPSR=0xe;
sfrb SPDR=0xf;
sfrb PIND=0x10;
sfrb DDRD=0x11;
sfrb PORTD=0x12;
sfrb PINC=0x13;
sfrb DDRC=0x14;
sfrb PORTC=0x15;
sfrb PINB=0x16;
sfrb DDRB=0x17;
sfrb PORTB=0x18;
sfrb PINA=0x19;
sfrb DDRA=0x1a;
sfrb PORTA=0x1b;
sfrb EECR=0x1c;
sfrb EEDR=0x1d;
sfrb EEARL=0x1e;
sfrb EEARH=0x1f;
sfrw EEAR=0x1e;   // 16 bit access
sfrb UBRRH=0x20;
sfrb UCSRC=0X20;
sfrb WDTCR=0x21;
sfrb ASSR=0x22;
sfrb OCR2=0x23;
sfrb TCNT2=0x24;
sfrb TCCR2=0x25;
sfrb ICR1L=0x26;
sfrb ICR1H=0x27;
sfrb OCR1BL=0x28;
sfrb OCR1BH=0x29;
sfrw OCR1B=0x28;  // 16 bit access
sfrb OCR1AL=0x2a;
sfrb OCR1AH=0x2b;
sfrw OCR1A=0x2a;  // 16 bit access
sfrb TCNT1L=0x2c;
sfrb TCNT1H=0x2d;
sfrw TCNT1=0x2c;  // 16 bit access
sfrb TCCR1B=0x2e;
sfrb TCCR1A=0x2f;
sfrb SFIOR=0x30;
sfrb OSCCAL=0x31;
sfrb OCDR=0x31;
sfrb TCNT0=0x32;
sfrb TCCR0=0x33;
sfrb MCUCSR=0x34;
sfrb MCUCR=0x35;
sfrb TWCR=0x36;
sfrb SPMCR=0x37;
sfrb TIFR=0x38;
sfrb TIMSK=0x39;
sfrb GIFR=0x3a;
sfrb GICR=0x3b;
sfrb OCR0=0X3c;
sfrb SPL=0x3d;
sfrb SPH=0x3e;
sfrb SREG=0x3f;
#pragma used-

// Interrupt vectors definitions


// Needed by the power management functions (sleep.h)
#asm
	#ifndef __SLEEP_DEFINED__
	#define __SLEEP_DEFINED__
	.EQU __se_bit=0x40
	.EQU __sm_mask=0xB0
	.EQU __sm_powerdown=0x20
	.EQU __sm_powersave=0x30
	.EQU __sm_standby=0xA0
	.EQU __sm_ext_standby=0xB0
	.EQU __sm_adc_noise_red=0x10
	.SET power_ctrl_reg=mcucr
	#endif
#endasm



flash unsigned char auc_SinParam[128] = {
128,134,140,147,153,159,165,171,177,182,188,193,198,204,208,213,
218,222,226,230,233,237,240,242,245,247,249,251,252,253,254,254,
254,254,253,252,251,250,248,246,244,241,238,235,232,228,224,220,
215,211,206,201,196,191,185,179,174,168,162,156,150,144,137,131,
125,119,112,106,100,94,88,82,77,71,65,60,55,50,45,41,
36,32,28,24,21,18,15,12,10,8,6,5,4,3,2,2,
2,2,3,4,5,7,9,11,14,16,19,23,26,30,34,38,
43,48,52,57,63,68,74,79,85,91,97,103,109,116,122,128}; 	// 128点正弦波样本值

unsigned char x_SW = 8,X_LUT = 0;

// T/C0 溢出中断服务
interrupt [10] void timer0_ovf_isr(void)
{
    X_LUT += x_SW;  				// 新样点指针
	if (X_LUT > 127) X_LUT -= 128;	// 样点指针调整
	OCR0 = auc_SinParam[X_LUT];		// 取样点指针到比较匹配寄存器
	//OCR0+=1;
}

void main(void)
{
	DDRB=0x08;					// PB3输出方式，作为OC0输出PWM波
	// Timer/Counter 0 initialization
	// Clock source: System Clock
	// Clock value: 4000.000 kHz
	// Mode: Fast PWM top=FFh
	// OC0 output: Non-Inverted PWM
	TCCR0=0x69;
	OCR0=128;

	TIMSK=0x01;					// 允许T/C0溢出中断
	#asm("sei")					// 开放全局中断

	while (1)
    {};
}