原创 CVAVR生成的典型USART收发的接口程序

 2008-12-15 21:31  5478 30 30 分类: MCU/ 嵌入式

一般教科书上提供的UART收发的程序往往是一段采用轮循（Polling）方式完成收发的简单代码。但对于高速的AVR来讲，采用这种方式大大降低了MUC的效率。在使用AVR时，应根据芯片本身的特点（片内大容量数据存储器RAM，更适合采用高级语言编写系统程序），编写高效可靠的UART收发接口（低层）程序。下面是一个典型的USART的接口程序。(下面是CodeVisionAVR修改成WINAVR后的程序,原来的程序请看底下给出的链界,在<a href="http://www.ouravr.com/">http://www.ouravr.com/</a>的论坛里) /***************************************************** <div style="border-right:.5pt solid;padding-right:5.4pt;border-top:.5pt solid;padding-left:5.4pt;background:#e6e6e6;padding-bottom:4px;border-left:.5pt solid;width:95%;padding-top:4px;border-bottom:.5pt solid;"> <div><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//usart.h <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//常量定义 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define BAUDRATE        9600    //波特率 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//#define F_CPU            4000000  //晶振频率4.0MHz <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RXB8 1 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define TXB8 0 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define PE 2    //M16 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//#define UPE 2    //M128 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define OVR 3 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define FE 4 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define UDRE 5 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RXC 7 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//宏定义 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define FRAMING_ERROR (1<<FE) <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define PARITY_ERROR (1<<PE)    //M16 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//#define PARITY_ERROR (1<<UPE)    //M128 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define DATA_OVERRUN (1<<OVR) <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define DATA_REGISTER_EMPTY (1<<UDRE) <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RX_COMPLETE (1<<RXC) <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// USART Receiver buffer <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// 全局变量,会在中断服务程序中被修改，须加volatile限定，不要就会出错啦 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RX_BUFFER_SIZE 16         // 接收缓冲区大小，可根据需要修改 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />volatile char rx_buffer[RX_BUFFER_SIZE]; // 接收缓冲区，为char型变量组成的数组，该数组构成环形队列，个数为RX_BUFFER_SIZE  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />volatile unsigned char rx_wr_index,rx_rd_index,rx_counter; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// This flag is set on USART Receiver buffer overflow <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />volatile char rx_buffer_overflow;   //接收缓冲区溢出标志 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// USART Transmitter buffer <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define TX_BUFFER_SIZE 16 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />volatile char tx_buffer[TX_BUFFER_SIZE]; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />volatile unsigned char tx_wr_index,tx_rd_index,tx_counter; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// 函数声明 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />char get_c(void); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void put_c(char c); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void put_s(char *ptr); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void init_USART(void);</div></div>   <div style="border-right:.5pt solid;padding-right:5.4pt;border-top:.5pt solid;padding-left:5.4pt;background:#e6e6e6;padding-bottom:4px;border-left:.5pt solid;width:95%;padding-top:4px;border-bottom:.5pt solid;"> <div><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//usart.c <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include <avr/io.h> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include <stdio.h> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include <avr/interrupt.h> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include "usart.h" <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />/**//*接收中断*/ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />ISR(USART_RXC_vect) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    char status,data; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    status=UCSRA;     //读取接收状态标志位，必须先读，当读了UDR后，UCSRA便自动清零了   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    data=UDR;         //读取USART数据寄存器，这句与上句位置不能颠倒的 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    if ((status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN))==0)     //判断本接收到的数据是否有数据帧、校验或数据溢出错误（此处指USART的硬件接收溢出） <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />       ...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           rx_buffer[rx_wr_index]=data;   // 将数据填充到接收缓冲队列中 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           if (++rx_wr_index == RX_BUFFER_SIZE)    //写指针指向下一个单元，并判断是否到了队列的尾部，（不表示接受缓冲区是否满！） <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />               rx_wr_index=0;  //到了尾部，则指向头部（构成环状） <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           if (++rx_counter == RX_BUFFER_SIZE)     //队列中收到字符加1，并判断是否队列已满  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />          ...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />              rx_counter=0;   // 队列满了，队列中收到字符个数为0，表示队列中所有以前的数据作废，因为最后的数据已经把最前边的数据覆盖了 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />              rx_buffer_overflow=1;        //置缓冲区溢出标志。在主程序中必要的地方需要判断该标志，以证明读到数据的完整性 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />          }; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />       }; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />} <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />/**//*接收单个字符*/ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />char get_c(void) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    char data; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    while (rx_counter==0);             //接收数据队列中没有数据可以读取，等待......（注2） <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    data=rx_buffer[rx_rd_index];       //读取缓冲队列中的数据 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    if (++rx_rd_index == RX_BUFFER_SIZE) rx_rd_index=0;     //读取指针指向下一个未读的数据，如果指到了队列尾部，则指回到队列头步 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    cli();    // 关中断！非常重要 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    --rx_counter;  //队列中未读数据个数减1。因为该变量在接收中断中要改变的，为了防止冲突，所以改动前临时关闭中断。程序相当可靠了。 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    sei();    // 开中断 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    return data; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />} <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//发送中断 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />ISR(USART_TXC_vect) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    if (tx_counter) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />    ...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           --tx_counter; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           UDR=tx_buffer[tx_rd_index]; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           if (++tx_rd_index == TX_BUFFER_SIZE) tx_rd_index=0; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />    };  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />} <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />/**//*发送单个字符*/ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void put_c(char c) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    while (tx_counter == TX_BUFFER_SIZE);   //发送数据队列中还有数据没有发送完，等待 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    cli(); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    if (tx_counter || ((UCSRA & DATA_REGISTER_EMPTY)==0))    //若发送数据队列有数据或者数据寄存器UDR非空时执行(因为队列先进先出的原因，所以，c要放进非空的发送数据队列里面) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />       ...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           tx_buffer[tx_wr_index]=c; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           if (++tx_wr_index == TX_BUFFER_SIZE) tx_wr_index=0; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           ++tx_counter; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />       } <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    else <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />           UDR=c; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    sei(); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />} <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />/**//*发送字符串*/ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void put_s(char *ptr) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    while (*ptr) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />    ...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        put_c(*ptr++); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />    } <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    put_c(0x0D); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    put_c(0x0A);  //结尾发送回车换行 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />} <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />/**//*USART 初始化*/ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void init_USART(void) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    //USART 9600 8, n,1  PC上位机软件(超级终端等)也要设成同样的设置才能通讯 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    UCSRC = (1<<URSEL) | 0x06; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    UBRRL= (F_CPU/BAUDRATE/16-1)%256; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    UBRRH= (F_CPU/BAUDRATE/16-1)/256; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    UCSRA = 0x00; <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    //接收使能，发送使能，接收中断使能，发送中断使能 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    UCSRB=(1<<RXCIE)|(1<<TXCIE)|(1<<RXEN)|(1<<TXEN); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />} <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /></div></div>   <div style="border-right:.5pt solid;padding-right:5.4pt;border-top:.5pt solid;padding-left:5.4pt;background:#e6e6e6;padding-bottom:4px;border-left:.5pt solid;width:95%;padding-top:4px;border-bottom:.5pt solid;"> <div><img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />/**//*********************************************** <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 名  称：AVR USART（RS232）低层驱动+中间层软件示例         <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />****                                           <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 作  者：zhiyu                        <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 编译器：WINAVR20070525                    <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />****                                          <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 参  考：http://www.ouravr.com/bbs/bbs_content.jsp?mother_form=bbs_content.jsp&bbs_id=1000&bbs_page_no=1&bbs_sn=147242 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />             《高档8位单片机ATmega128原理与开发应用指南（上）》--马潮  P320 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />             《嵌入式C编程与ATMEL AVR》-- 国外计算机经典教材 P141 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 日  期：2007.07.19 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 芯  片：M16L <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 时钟源：外部4M晶振 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 结  果：测试成功 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />**** 问  题：暂无 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />***********************************************/ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//#include <avr/io.h> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//#include <stdio.h> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include <avr/interrupt.h> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include "usart.h" <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />int main(void) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    init_USART(); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    sei();    //总中断允许 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />     <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    put_s("Hello！"); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    put_s("这是一个简单的高速的串口驱动程序"); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    put_s("请你输入任意的字符，单片机将返回你输入的字符"); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    while (1) <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />    ...{ <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        put_c(get_c()); <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />    } <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />}</div></div>   <div style="border-right:.5pt solid;padding-right:5.4pt;border-top:.5pt solid;padding-left:5.4pt;background:#e6e6e6;padding-bottom:4px;border-left:.5pt solid;width:95%;padding-top:4px;border-bottom:.5pt solid;"> <div><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />//Makefile,主要的几项,只是针对我这里的程序,要灵活运用哦 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />MCU = atmega16 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />F_CPU = 4000000 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />TARGET = main <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />SRC = $(TARGET).c usart.c   //多文件编译才会用到这一项，可以参考这个帖子: <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />http://www.mcublog.com/blog/user1/4266/archives/2006/6145.html</div></div> *****************************************************/  这段由CVAVR程序生成器产生的UART接口代码是一个非常好的、高效可靠，并且值得认真学习和体会的。其特点如下：    l.它采用两个8字节的接收和发送缓冲器来提高MCU的效率.当主程序调用getchar()函数时,按顺序执行到while (rx_counter==0)处,接收数据队列里面就没有数据,如果再没有数据输入,那么就只能死在那里等待.如果有数据输入的话,中断很快就响应,数据就会迅速地填充接收数据队列,rx_counter!=0,这个死等待也就给瓦解了,让程序执行接下来的那句data=rx_buffer[rx_rd_index]了.最后return data;,返回输入的值;如当主程序调用Putchar()发送数据时，如果UART口不空闲，就将数据放入发送缓冲器中，MCU不必等待，可以继续执行其它的工作。而UART的硬件发送完一个数据后，产生中断，由中断服务程序负责将发送缓冲器中数据依次自动送出。 C语言书本里有其中一段:       getchar()函数(字符输入函数)的作用是从终端(或系统隐含指定的输入设备)输入一个字符.getchar()函数没有参数.当你输入一个字符时候,比如'a'后,要按'Enter'键,字符才能送到内存!你一旦按了这个'Enter',上面的程序就会执行中断响应了,    2.数据缓冲器结构是一个线性的循环队列，由读、写和队列计数器3个指针控制，用于判断队列是否空、溢出，以及当前数据在队列中的位置。    3.用编译控制命令#pragma savereg-和#pragma savereg+，使得由CVAVR在生成的中断服务程序中不进行中断保护（CVAVR生成中断保护会将比较多的寄存器压入堆栈中），而在中断中嵌入汇编，只将5个在本中断中必须要保护的寄存器压栈。这样提高了UART中断处理的速度，也意味着提高了MCU的效率。    4.由于在接口程序Putchar()、Getchar()和中断服务程序中都要对数据缓冲器的读、写和队列计数器3个指针判断和操作，为了防止冲突，在Putchar()、Getchar()中对3个指针操作时临时将中断关闭，提高了程序的可靠性。     建议读者能逐字逐句地仔细分析该段代码，真正理解和领会每一句语句（包括编译控制命令的作用）的作用，从中体会和学习如何编写效率高，可靠性好，结构优良的系统代码。这段程序使用的方法和技巧，对编写SPI、I2C的串行通信接口程序都是非常好的借鉴。     作为现在的单片机和嵌入式系统的工程师，不仅要深入全面的掌握芯片和各种器件的性能，具备丰富的硬件设计能力；同时也必须提高软件的设计能力。要学习和掌握有关数据结构、操作系统、软件工程、网络协议等方面的知识，具有设计编写大的复杂系统程序的能力。 /*================================================= 链接: <a href="http://www.ouravr.com/bbs/bbs_content.jsp?bbs_sn=147242&bbs_page_no=1&sub_kind_id=1430&bbs_id=1000">http://www.ouravr.com/bbs/bbs_content.jsp?bbs_sn=147242&bbs_page_no=1&sub_kind_id=1430&bbs_id=1000</a> <a href="http://www2.ouravr.com/bbs/bbs_content.jsp?%20mother_form=bbs_content.jsp&amp;bbs_id=1000&amp;bbs_page_no=1&amp;bbs_sn=528742">http://www2.ouravr.com/bbs/bbs_content.jsp? mother_form=bbs_content.jsp&amp;bbs_id=1000&amp;bbs_page_no=1&amp;bbs_sn=528742</a> <a href="http://bbs.avrvi.com/simple/index.php?t3193.html">http://bbs.avrvi.com/simple/index.php?t3193.html</a> 书籍: 高档8位单片机ATmega128原理与开发应用指南(上) P320          嵌入式C编程与Atmel AVR P141 第三章 标准I/O和预处理函数 (网上有这本电子书的下载) 下面是马潮老师的说法: 在CVAVR系统提供的标准库函数stdio.h中，提供了getchar()函数，该函数是采用轮询方式从USART接收数据的，轮询方式不仅效率低，而且会丢失数据，不能实现多任务的并行处理。 CVAVR程序向导中给出的采用中断+缓冲的方式接受数据，同PC的串口接收数据的方法一样，充分利用了AVR的高速和RAM多的优点，体现出了如何才能充分发挥AVR的特点的程序设计思想，这种思路在32位系统中也是这样的。 使用AVR的话，对软件的设计能力要求更高了，否则根本不能发挥和体现AVR的特点。许多人有了一点C的基础，就认为采用C编写单片机程序没问题，很快就会掌握AVR了，对此我只能一笑了之。看看本站上众多的代码，再看看本贴的遭遇，能说什么呢？ 还有,你可以参考一下这里的链接:<a href="http://www.iccavr.com/forum/dispbbs.asp?boardID=2&ID=2249&page=1">http://www.iccavr.com/forum/dispbbs.asp?boardID=2&ID=2249&page=1</a>这人朋友些得不错,主要是因为: <div style="border-right:.5pt solid;padding-right:5.4pt;border-top:.5pt solid;padding-left:5.4pt;background:#e6e6e6;padding-bottom:4px;border-left:.5pt solid;width:95%;padding-top:4px;border-bottom:.5pt solid;"> <div><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RX_BUFFER_SIZE0 8 //收件箱的长度 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />unsigned char rx_buffer0[RX_BUFFER_SIZE0];   //收信箱 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />unsigned char rx_wr_index0;   //收信箱写指针 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />unsigned char rx_rd_index0;   //收信箱读指针 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />unsigned char rx_counter0;    //收信箱存量 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />unsigned char rx_buffer_overflow0;  //收信箱满标志位 <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /></div></div>   这样的比喻不是很好理解了吗,你要是脑子发散一点,会不会想到操作系统里面的"管道"的概念呢,其实现在我也没具体去看这东西,不过也会有些相通的地方吧. 回到本题： 注1： 如果在程序的开头部分加上语句 #define _DEBUG_TERMINAL_IO_ 那么程序在编译时仍使用系统自己的getchar()函数，这样在软件模拟仿真时，可以从模拟的终端读取数据，便于在软件模拟环境中调试整个系统，而需要正式运行时，则把该句注释掉。 注2： 此处在正式应用中应根据实际情况做适当的修改。否则当主程序调用getchar()时，如果缓冲队列中没有数据，同时对方也没有发数据的情况时，程序会在此死循环。 比较简单的办法是将这句删掉，而在调用getchar()函数前先判断rx_counter的值，为0的话就不调用了。 或改为： <div style="border-right:.5pt solid;padding-right:5.4pt;border-top:.5pt solid;padding-left:5.4pt;background:#e6e6e6;padding-bottom:4px;border-left:.5pt solid;width:95%;padding-top:4px;border-bottom:.5pt solid;"> <div><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />  signed int getchar(void)   <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />  ...{   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    signed int data;   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    if (rx_counter == 0)  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />    ...{  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        data = -1;      <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />    }  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    else  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />    ...{  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        data=rx_buffer[rx_rd_index];   //读取缓冲队列中的数据   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        if (++rx_rd_index == RX_BUFFER_SIZE) rx_rd_index=0;  //读取指针指向下一个未读的数据，如果指到了队列尾部，则指回到队列头步   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        #asm("cli")      // 关中断！非常重要                                                <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        --rx_counter;    //队列中未读数据个数减1。因为该变量在接收中断中要改变的，为了防止冲突，所以改动前临时关闭中断。程序相当可靠了。   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />        #asm("sei")      // 开中断  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />    }  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />    return data;   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />} </div></div>   注3： 有兴趣希望深入实在学习的网友，可将CVAVR生成的USART发送代码仔细分析以下。它的发送代码非常完美，可以马上使用。 思考分析： <div style="border-right:.5pt solid;padding-right:5.4pt;border-top:.5pt solid;padding-left:5.4pt;background:#e6e6e6;padding-bottom:4px;border-left:.5pt solid;width:95%;padding-top:4px;border-bottom:.5pt solid;"> <div><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include <mega16.h>  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RXB8 1  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define TXB8 0  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define UPE 2  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define OVR 3  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define FE 4  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define UDRE 5  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RXC 7  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define FRAMING_ERROR (1<<FE)  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define PARITY_ERROR (1<<UPE)  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define DATA_OVERRUN (1<<OVR)  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define DATA_REGISTER_EMPTY (1<<UDRE)  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define RX_COMPLETE (1<<RXC)  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// USART Transmitter buffer  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define TX_BUFFER_SIZE 8  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />char tx_buffer[TX_BUFFER_SIZE];  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#if TX_BUFFER_SIZE<256  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />unsigned char tx_wr_index,tx_rd_index,tx_counter;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#else  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />unsigned int tx_wr_index,tx_rd_index,tx_counter;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#endif  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// USART Transmitter interrupt service routine  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />interrupt [USART_TXC] void usart_tx_isr(void)  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />if (tx_counter)  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />   ...{  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />   --tx_counter;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />   UDR=tx_buffer[tx_rd_index];  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />   if (++tx_rd_index == TX_BUFFER_SIZE) tx_rd_index=0;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />   };  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />}  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#ifndef _DEBUG_TERMINAL_IO_  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// Write a character to the USART Transmitter buffer  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#define _ALTERNATE_PUTCHAR_  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#pragma used+  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void putchar(char c)  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />while (tx_counter == TX_BUFFER_SIZE);  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />#asm("cli")  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />if (tx_counter || ((UCSRA & DATA_REGISTER_EMPTY)==0))  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockStart.gif" align="top" alt="ExpandedSubBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedSubBlock.gif" align="top" />   ...{  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />   tx_buffer[tx_wr_index]=c;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />   if (++tx_wr_index == TX_BUFFER_SIZE) tx_wr_index=0;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />   ++tx_counter;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedSubBlockEnd.gif" align="top" />   }  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />else  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />   UDR=c;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />#asm("sei")  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockEnd.gif" align="top" />}  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#pragma used-  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#endif  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// Standard Input/Output functions  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />#include <stdio.h>  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />// Declare your global variables here  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/None.gif" align="top" />void main(void)  <img src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ExpandedBlockStart.gif" align="top" alt="ExpandedBlockStart.gif" /><img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/ContractedBlock.gif" align="top" />...{  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Declare your local variables here  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Input/Output Ports initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Port A initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />PORTA=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />DDRA=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Port B initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />PORTB=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />DDRB=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Port C initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />PORTC=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />DDRC=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Port D initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T   <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />PORTD=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />DDRD=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Timer/Counter 0 initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Clock source: System Clock  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Clock value: Timer 0 Stopped  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Mode: Normal top=FFh  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// OC0 output: Disconnected  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />TCCR0=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />TCNT0=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />OCR0=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Timer/Counter 1 initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Clock source: System Clock  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Clock value: Timer 1 Stopped  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Mode: Normal top=FFFFh  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// OC1A output: Discon.  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// OC1B output: Discon.  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Noise Canceler: Off  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Input Capture on Falling Edge  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Timer 1 Overflow Interrupt: Off  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Input Capture Interrupt: Off  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Compare A Match Interrupt: Off  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Compare B Match Interrupt: Off  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />TCCR1A=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />TCCR1B=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />TCNT1H=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />TCNT1L=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />ICR1H=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />ICR1L=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />OCR1AH=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />OCR1AL=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />OCR1BH=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />OCR1BL=0x00;  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" /> <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Timer/Counter 2 initialization  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Clock source: System Clock  <img alt="" src="http://images.csdn.net/syntaxhighlighting/OutliningIndicators/InBlock.gif" align="top" />// Clock value: Timer 2 S</div></div>     <a href="http://blog.csdn.net/zhiyu520/archive/2007/09/21/1795332.aspx">http://blog.csdn.net/zhiyu520/archive/2007/09/21/1795332.aspx</a>原帖地址（一个大师）

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