UART收發(fā)的程序

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1、一般教科書上提供的UART收發(fā)的程序往往是一段采用輪循（Polling）方式完成收發(fā)的簡單代碼。但對于高速的AVR來講，采用這種方式大大降低了MUC的效率。在使用AVR時(shí)，應(yīng)根據(jù)芯片本身的特點(diǎn)（片內(nèi)大容量數(shù)據(jù)存儲器RAM，更適合采用高級語言編寫系統(tǒng)程序），編寫高效可靠的UART收發(fā)接口（低層）程序。下面是一個(gè)典型的ATmega128的軟件USART的接口程序。#include#defineRXB81#defineTXB80#defineUPE2#defineOVR3#defineFE4#defineUDRE5#defineRXC7#def

2、ineFRAMING_ERROR(1<

3、SART0Receiverbufferoverflowbitrx_buffer_overflow0;//USART0Receiverinterruptserviceroutine#pragmasavereg-interrupt[USART0_RXC]voiduart0_rx_isr(void){charstatus,data;#asm?????????pushr26????????????pushr27????????????pushr30????????????pushr31????????????in???r26,sreg????????????pushr

4、26#endasmstatus=UCSR0A;data=UDR0;if((status&(FRAMING_ERROR

5、PARITY_ERROR

6、DATA_OVERRUN))==0)???{???????rx_buffer0[rx_wr_index0]=data;???????if(++rx_wr_index0==RX_BUFFER_SIZE0)rx_wr_index0=0;???????if(++rx_counter0==RX_BUFFER_SIZE0)??????????{??????????????rx_counter0=0;??????????????r

7、x_buffer_overflow0=1;??????????};???};#asm???????pop??r26???????out??sreg,r26???????pop??r31???????pop??r30???????pop??r27???????pop??r26#endasm}#pragmasavereg+#ifndef_DEBUG_TERMINAL_IO_//GetacharacterfromtheUSART0Receiverbuffer#define_ALTERNATE_GETCHAR_#pragmaused+chargetchar(void)

8、{??chardata;??while(rx_counter0==0);??data=rx_buffer0[rx_rd_index0];??if(++rx_rd_index0==RX_BUFFER_SIZE0)rx_rd_index0=0;??#asm("cli")????--rx_counter0;??#asm("sei")??returndata;}#pragmaused-#endif//USART0Transmitterbuffer#defineTX_BUFFER_SIZE08chartx_buffer0[TX_BUFFER_SIZE0];unsigne

9、dchartx_wr_index0,tx_rd_index0,tx_counter0;//USART0Transmitterinterruptserviceroutine#pragmasavereg-interrupt[USART0_TXC]voiduart0_tx_isr(void){??#asm??????pushr26??????pushr27??????pushr30??????pushr31??????in???r26,sreg??????pushr26??#edasm??if(tx_counter0)??{?????????--tx_counter

10、0;???????UDR0=tx_bu