uart.c

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#include <intrins.h>
#include <REGX52.h>
#include "uart.h"


static unsigned char idata uartbuf;
static unsigned char idata bufwptr, bufrptr;
unsigned char idata uartbuff[UARTBUFFLEN];

static unsigned char code BAUD[] = {0xB8, 0xDC, 0xEE, 0xF7, 0xFA, 0xFD};


void UartInit(unsigned char baudrate)
{
	ES = 0;
	TR2 = 0;

	bufwptr = 0;					// 写指针
	bufrptr = 0;					// 读指针

	PCON = 0x00;					// 设置串口波特率, 时钟频率30MHZ
	T2CON = 0x30;					// 定时器2作为波特率发生器
	SCON = 0x50;					// 模式1
									// n = 65536 - [fosc/baud*32]
									// n = 65536 - 22118400/(57600*32) = 65536 - 12 = 65524 = 0xfff4
	RCAP2H = 0xff;					
	RCAP2L = BAUD[baudrate];		// baud rate 57600			
	TH2 = 0xff;
	TL2 = BAUD[baudrate];

	IP = 0x10;						// 串口中断优先级高
	REN = 1;
	TI = 0;
	RI = 0;
	TR2 = 1;						// 启动定时器2
	ES = 1;							// 使能串口中断
}

/*
 *  发送一个字节数据 
 */ 
void SendChar(unsigned char ch)
{
	SBUF = ch;
	while(TI == 0);
	TI = 0;
}

/*
 * 发送字符串
*/
void SendString(char *str)
{
	while(*str)
	{
		SendChar(*str);
		str++;
	}
}

/*
 *	判断是否接收到数据，如果没有返回0，如果有，返回数据长度
 */
unsigned char IsUartReceived(void)
{
	unsigned char num;
	
	EA = 0;							// 关中断
	if(bufwptr == bufrptr)
		num = 0;
	else if(bufwptr > bufrptr)
		num = (bufwptr-bufrptr);
	else // if(bufwptr < bufrptr) 
		num = (UARTBUFFLEN-bufwptr+bufrptr);
	EA = 1;
	return num;
}

/*
 *	从缓冲区中读一个字节数据
 *	返回剩下的字节数
 */
unsigned char ReadChar(unsigned char idata *buf)
{
	unsigned char ch, num;

	EA = 0;
	if(bufwptr == bufrptr)
	{
		*buf = 0;
		num = 0;
	}
	else if(bufwptr > bufrptr)
	{
		ch = uartbuff[bufrptr];
		*buf = ch;
		bufrptr++;
		num = (bufwptr-bufrptr);
	}
	else	// if(bufwptr < bufrptr) 
	{
		ch = uartbuff[bufrptr];
		*buf = ch;
		bufrptr++;
		if(bufrptr == UARTBUFFLEN)
			bufrptr = 0;
		num = (UARTBUFFLEN-bufrptr+bufwptr);
	}

	EA = 1;
	return num;
}


/*
 *	串口中断接受 
 */
void UartInt(void) interrupt 4 using 1
{
	if(RI)
	{
		ES = 0;
		uartbuf = SBUF;
		RI = 0;							 // 清中断标志
		
		uartbuff[bufwptr] = uartbuf;	// 数据写入缓冲区
		if(bufwptr >= UARTBUFFLEN-1)	// 循环缓冲指针
			bufwptr = 0;
		else
			bufwptr++;
		if(bufwptr == bufrptr)			// 未读数据被覆盖，读指针更新到写指针的上一个单元
			bufrptr = bufwptr + 1;

		ES = 1;
	}
}