usart.c

这是利用atmega对usart的设计程序

#include <iom64.h>
#include <intrinsics.h>

#define F_CPU	8		//8MHz时钟频率
#define	delay_us(t_nus)	__delay_cycles(t_nus*F_CPU)
#define delay_ms(t_nms)	__delay_cycles(t_nms*F_CPU*1000)

/*USART1多机模式中断方式接受数据*/
unsigned char me_address;
unsigned char me_data;

void uart1_init(void)	//usart初始化
{
  UBRR1L=0x33;	//波特率为9600bit/s 
  UBRR1H=0x00;	
  //U2X=0时BANDRATE的计算公式
  //UBRRnL=(F_CPU/BAUDRATE/16-1)%256
  //UBRRnH=(F_CPU/BAUDRATE/16-1)/256
  UCSR1B=(1<<RXEN1)|(1<<TXEN1)|(1<<UCSZ12)|(1<<RXCIE1);	//允许发送接收，使能接受中断
  UCSR1C=(1<<UCSZ11)|(1<<UCSZ10);	//九位数据+1位stop
}
unsigned char F_receivechar(void)
{
  while(!(UCSR1A&(1<<RXC1)));
  return UDR1;
}

void F_485mpcm1(void)	//多机模式设定
{
  UCSR1A|=(1<<MPCM1);
  UCSR1B|=(1<<RXCIE1);
}
void F_485mpcm0(void)	//通信状态，清MPCM
{
  UCSR1A&=~(1<<MPCM1);
  UCSR1B&=~(1<<RXCIE1);
}
#pragma vector=USART1_RXC_vect
__interrupt void uart1_RXD(void)
{
  unsigned char receive_address;
  receive_address=UDR0;
  if(receive_address==me_address)
  {
	F_485mpcm0();
	me_data=F_receivechar();
	F_485mpcm1();
  }
}
/*字符处理函数*/
void put_c(unsigned char c)	//字符输出 查询方式发送
{
  while(!(UCSR0A&(1<<UDRE0)));
  UDR0=c;
}
void put_str(char *pstr)
{
  while(*pstr)
  {
	put_c(*pstr);
	pstr++;
  }
  put_c(0x0a);	//换行
  put_c(0x0d);
}  
unsigned char get_c(void)	//字符输入
{
  unsigned int i=0;
  while(!(UCSR0A&(1<<RXC0)))
  {
	if(i>500)	//等待500ms 没有数据返回
	  break;
	delay_ms(1);
	i++;
  }
  return UDR0;
}
/*多机模式，从机中断接收，有地址、命令（接受发送）和应答主机功能*/
unsigned char addr;
void uart10_init(void)	//usart初始化
{
  UBRR1L=0x33;	//波特率为9600bit/s 
  UBRR1H=0x00;	
  //U2X=0时BANDRATE的计算公式
  //UBRRnL=(F_CPU/BAUDRATE/16-1)%256
  //UBRRnH=(F_CPU/BAUDRATE/16-1)/256
  UCSR1B=(1<<RXEN1)|(1<<TXEN1)|(1<<UCSZ12)|(1<<RXCIE1);	//允许发送接收，使能接受中断
  UCSR1C=(1<<UCSZ11)|(1<<UCSZ10);	//九位数据+1位stop
}

void F_mpcm1(void)	//多机模式设定
{
  UCSR1A|=(1<<MPCM1);
  UCSR1B|=(1<<RXCIE1);
}
void F_mpcm0(void)	//通信状态，清MPCM
{
  UCSR1A&=~(1<<MPCM1);
  UCSR1B&=~(1<<RXCIE1);
}
void function1(void)
{
  ;
}
void function2(void)
{
  ;
}
void function3(void)
{
  ;
}
void function4(void)
{
  ;
}

#pragma vector=USART0_RXC_vect
__interrupt void uart0_RXD(void)
{
  unsigned char uc_addr;
  unsigned char uc_cmd;
  unsigned char uc_cleck;
  unsigned char uc_count;
  UCSR0B&=0x7F;	//清RXCIE0中断
  uc_count=0;
  uc_addr=UDR0;
  //接收到本机地址
  if(uc_addr==addr)
  {
	F_mpcm0();
	put_c(addr);	//回送本机地址
	uc_cmd=get_c();		//接受命令
	switch(uc_cmd)
	{
	case 0x01:	//命令1
	  uc_count=0;
	  function1();	//调用命令1函数
	  uc_cleck=get_c();
	  while((uc_cleck!=0x55)&&(uc_count<3))
	  {
		function1();
		uc_cleck=get_c();
		uc_count++;
	  }
	  break;
	case 0x02:
	  uc_count=0;
	  function2();
	  uc_cleck=get_c();
	  while((uc_cleck!=0x55)&&(uc_count<3))
	  {
		function2();
		uc_cleck=get_c();
		uc_count++;
	  }
	  break;
	case 0x03:
	  uc_count=0;
	  function3();
	  uc_cleck=get_c();
	  while((uc_cleck!=0x55)&&(uc_count<3))
	  {
		function3();
		uc_cleck=get_c();
		uc_count++;
	  }
	  break;
	case 0x04:
	  uc_count=0;
	  function4();
	  uc_cleck=get_c();
	  while((uc_cleck!=0x55)&&(uc_count<3))
	  {
		function4();
		uc_cleck=get_c();
		uc_count++;
	  }
	  break;
	default:break;
	}
  }
  else
  {;}
  F_mpcm1();
  UCSR0B|=0x80;
  SREG|=0x80;
}
/*调用的CRC函数*/
const static unsigned int crc_tbl[256]={
  0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
  0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
  0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
  0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
  0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
  0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
  0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
  0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
  0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
  0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
  0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
  0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
  0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
  0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
  0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
  0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
  0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
  0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
  0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
  0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
  0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
  0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
  0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
  0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
  0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
  0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
  0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
  0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
  0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
  0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
  0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
  0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
};
unsigned int getcrc(unsigned char *date,unsigned int len)
{
  unsigned int crc;
  unsigned char temp;
  crc=0;
  while(len!=0)
  {
	temp=(crc/256);	//8位二进制数暂存CRC的高8位
	crc<<=8;	//左移8位
	/*高8位和当前字节相加后再查表求CRC，再加上以前的CRC*/
	crc^=crc_tbl[temp^(*date)];
	date++;
	len--;
  }
  return crc;
}

/*USART0查询发送中断接受*/
void uart0_init(void)	//uart0初始化
{
  UBRR1L=0x33;	//波特率为9600bit/s
  UBRR1H=0x00;
  UCSR0B=UCSR1B=(1<<RXEN1)|(1<<TXEN1)|(0<<UCSZ12)|(1<<RXCIE1);
  UCSR0C=(1<<UCSZ01)|(1<<UCSZ00);//8位数据1位stop
}

  
void main(void)
{
  uart1_init();
  F_485mpcm1();
  SREG|=0x80;
  while(1);
}