详解一个非常好的串口程序：Mega128

#i nclude

#i nclude

#i nclude "UART.h"

/* USART Buffer Defines */

#define USART_RX_BUFFER_SIZE 16 /* 1,2,4,8,16,32,64,128 or 256

bytes */

#define USART_RX_BUFFER_MASK ( USART_RX_BUFFER_SIZE - 1 )

#define USART_TX_BUFFER_SIZE 16 /* 1,2,4,8,16,32,64,128 or 256

bytes */

#define USART_TX_BUFFER_MASK ( USART_TX_BUFFER_SIZE - 1 )

#if ( USART_RX_BUFFER_SIZE & USART_RX_BUFFER_MASK )

#error RX buffer size is not a power of 2

#endif

/* StatIC Variables */

static unsigned char USART_RxBuf[USART_RX_BUFFER_SIZE];

static volatile unsigned char USART_RxHead;

static volatile unsigned char USART_RxTail;

static unsigned char USART_TxBuf[USART_TX_BUFFER_SIZE];

static volatile unsigned char USART_TxHead;

static volatile unsigned char USART_TxTail;

/* 串口初始化 */

void InitUSART(INT8U baudrate)

{

INT8U x;

UBRR0L = baudrate;

UCSR0B = ( (1

Interrupt Enable, Receiver Enable and Transmitter Enable*/

x = 0; /* flush receive buffer */

USART_RxTail = x;

USART_RxHead = x;

USART_TxTail = x;

USART_TxHead = x;

}

/* 接收中断 */

void USART_RX_interrupt( void )

{

unsigned char data;

unsigned char tmphead;

data = UDR0; /* read the received data */

tmphead = ( USART_RxHead + 1 ) & USART_RX_BUFFER_MASK;/*

calculate

buffer index */

USART_RxHead = tmphead; /* store new index */

if ( tmphead == USART_RxTail )

{

return;/* ERROR! Receive buffer overflow, you CAN use

flux cortorl */

}

USART_RxBuf[tmphead] = data; /* store received data in buffer

*/

}

/* 发送中断 */

void USART_TX_interrupt( void )

{

unsigned char tmptail;

if ( USART_TxHead != USART_TxTail )/* check if all data is

transmitted */

{

tmptail = ( USART_TxTail + 1 ) & USART_TX_BUFFER_MASK;/*

calculate buffer index */

USART_TxTail = tmptail; /* store new index */

UDR0 = USART_TxBuf[tmptail]; /* start transmition */

}

else

{

UCSR0B &= ~(1

}

}

/* 读取数据函数 */

unsigned char ReceiveByte( void )

{

unsigned char tmptail;

while ( USART_RxHead == USART_RxTail ) /* wait for incomming

data */

;

tmptail = ( USART_RxTail + 1 ) & USART_RX_BUFFER_MASK;/*

calculate

buffer index */

USART_RxTail = tmptail; /* store new index */

return USART_RxBuf[tmptail]; /* return data */

}

/* 发送数据函数 */

void TransmitByte( unsigned char data )

{

unsigned char tmphead;

tmphead = ( USART_TxHead + 1 ) & USART_TX_BUFFER_MASK; /*

calculate

buffer index */

while ( tmphead == USART_TxTail )/* wait for free sPACe in

buffer */

;

USART_TxBuf[tmphead] = data; /* store data in buffer */

USART_TxHead = tmphead; /* store new index */

UCSR0B |= (1<}

/* 查询是否有数据 */

unsigned char DataInReceiveBuffer( void )

{

return ( USART_RxHead != USART_RxTail ); /* return 0 (FALSE)

if the

receive buffer is empty */

}

/* 中断中只做很少的事情，通常我是在接收中断中post一个信号量，触发别的任务读数据

*/