usart串口通讯例子.i

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/*****************************************************
CodeWizardAVR V1.24.8d Professional
Clock frequency     : 7.372800 MHz

波特率9600/8个数据位 /1个停止位 /无校验
实验板硬件设置
1: J5的2个跳线帽短接,使用外部晶振7.3728MHz(需要设置熔丝)
2: R和T分别插上跳线帽,使用MAX232,其他跳线开路
3: DB9接口连接到电脑
请配合串口调试软件SSCOM32或者comdebug进行调试
*/
// CodeVisionAVR C Compiler
// (C) 1998-2004 Pavel Haiduc, HP InfoTech S.R.L.

// I/O registers definitions for the ATmega8


#pragma used+
#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 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;
sfrw ICR1=0x26;   // 16 bit access
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 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 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=0x80
	.EQU __sm_mask=0x70
	.EQU __sm_powerdown=0x20
	.EQU __sm_powersave=0x30
	.EQU __sm_standby=0x60
	.EQU __sm_ext_standby=0x70
	.EQU __sm_adc_noise_red=0x10
	.SET power_ctrl_reg=mcucr
	#endif
#endasm



/*串口初始化函数*/
void Uart_Init(void) {
  UCSRB=0x18;                 //下面是3条语句是串口初始化语句
  UCSRC=0x06;
  UBRRH=0x00; 
  UBRRL=0x2F; 
}

/*数/*数据发送，查询方式*/
void uart_transmit(unsigned char i) {
 //PORTD |= (1 << PD2);      /*设置RS485为输出状态*/
 UDR = i;         /* 发送数据*/
 while (!(UCSRA & (1<<TXC)));    /* 等待发送缓冲器为空*/
 UCSRA |= (1 << TXC);      /*清除发送标志*/
 //PORTD &= ~(1 << PD2);      /*设置RS485为输入状态*/
}
/*数据接收，查询方式*/
unsigned char uart_receive( void ) {
 while (!(UCSRA & (1<<RXC)));    /* 等待接收数据*/
 return UDR;         /* 获取并返回数据*/
}


/*主函数*/
void main(void) {

	unsigned char temp;
	Uart_Init();
	
	while (1) {
		temp = Uart_Receive();		/*等待接收数据*/
		PORTB = ~temp;	   		/*显示低电平有效*/
		Uart_Transmit(temp);		/*发送收到的数据*/
		}
}