1、在工作中經常將平臺的串口和PC機連接，通過串口打印信息進行程序調試。LPC1788共有5個串口Uart0-Uart4,跟具開發板的資源，將使用Uart2進行簡單的串口輸出和輸入中斷的操作。開發板上使用74HC4052多路開關對UART2的RXD和TXD進行選擇，使用SP3243E進彳f3.0V到5.5V的RS-232電平轉換。查看手冊配置好相關的跳線帽，保證DB口上的串口輸出采用的是Uart2。下面介紹Uart相關系統配置和Uart模塊的配置。Uart的時鐘采用PCLK,我們配置系統的CCLK為120M,PCLK為60M,后面設置串口的波特率就采用PLCK進行計算要使用串口2的功能需要使能系統

2、時鐘控制PCONP,以及配置GPIO管腳為Uart2的RXD和TXD功能。要實現通信，我們需要設置數據的格式，包括傳輸的波特率，數據長度，停止位，以及校驗等，這些數據在線性控制寄存器UnLCR中控制。波特率的產生需要經過分數波特率分頻器UnFDR和主分頻器DLL,DLM。計數公式如下圖。PCLKWWW/心茂(25axCir)LM十CmLi根據計算，當PLCK=60M,波特率為115200,數據位為8,停止位為1,無校驗，則DLL=22,DLM=0,DivAddVal=1,MulVal=2,線性控制寄存器中的值為0x3要通過串口發送數據時，只需要把要發送的數據寫入發送保持寄存器UnTHR,系統就

3、會通過移位寄存器將數據通過串口發送。為了了解系統的發送狀態，還需要線性狀態寄存器UnLSR,例如程序中使用I該寄存器的第5位判斷發慫保持寄存器是否為空，防止數據溢出。如果需要進行串口的中斷操作，還需要對串口中斷進行配置，如串口中斷使能寄存器UnIER和串口中斷標識寄存器UnIIR。程序中使用到了串口2的接收中斷，為此在中斷使能設置寄存器ISER中使能UART2中斷，在串口中斷使能寄存器UnIER中使能串口的接收中斷，該中斷同時使能了字符接收超時中斷。UART2的RXD管腳接收到數據將存放在FIFO中，程序中配置接收FIFO的觸發條件為1個字節，即有接收到數據就觸發。中斷觸發后，我們可以根據中斷

4、標識寄存器UnIIR判斷到底是串口的接收中斷，超時中斷，發送中斷等。進入中斷以后，接收中斷和超時中斷，都可以通過讀取接收緩存寄存器UnRBR進行中斷復位，使下次中斷可以發生。下面的程序例子，程序開始打印菜單，PC用口軟件發送一個字節數據給開發板，開發板接收到數據后將讀取UnRBR前后的中斷標識寄存器IIR的值，以及接收到的值發送回給PC。如果是0x5a或者0xa5還可以打開或者關閉LED指示燈。#defineCCLK120000000#definePCLK60000000#definerFIOIDIR(*(volatileunsigned*)(0x20098020)#definerFIO1MA

5、SK(*(volatileunsigned*)(0x20098030)#definerFIO1PIN(*(volatileunsigned*)(0x20098034)#definerFIO1SET(*(volatileunsigned*)(0x20098038)#definerFIO1CLR(*(volatileunsigned*)(0x2009803c)#definerISER0(*(volatileunsigned*)(0xE000E100)#definerCLKSRCSEL(*(volatileunsigned*)(0x400FC10C)/時鐘源選擇寄存器#definerPLL0CON(

6、*(volatileunsigned*)(0x400FC080)/PLL0控制寄存器#definerPLL0CFG(*(volatileunsigned*)(0x400FC084)/PLL0配置寄存器#definerPLL0STAT(*(volatileunsigned*)(0x400FC088)/PLL0狀態寄存器#definerPLL0FEED(*(volatileunsigned*)(0x400FC08C)/PLL0饋送寄存器#definerPLL1CON(*(volatileunsigned*)(0x400FC0A0)#definerPLL1CFG(*(volatileunsigned

7、*)(0x400FC0A4)#definerPLL1STAT(*(volatileunsigned*)(0x400FC0A8)#definerPLL1FEED(*(volatileunsigned*)(0x400FC0AC)#definerCCLKSEL(*(volatileunsigned*)(0x400FC104)/CPU時鐘選擇寄存器#definerUSBCLKSEL(*(volatileunsigned*)(0x400FC108)/USB時鐘選擇寄存器#definerPCLKSEL(*(volatileunsigned*)(0x400FC1A8)/外設時鐘寄存器#definerPCON

8、(*(volatileunsigned*)(0x400FC0C0)#definerPXCONP(*(volatileunsigned*)(0x400FC0C4)#definerSCS(*(volatileunsigned*)(0x400FC1A0)/系統控制和狀態寄存器#definerCLKOUTCFG(*(volatileunsigned*)(0x400FC1C8)#definerIOCON_P0_10(*(volatileunsigned*)(0x4002C028)#definerIOCONP011(*(volatileunsigned*)(0x4002C02C)#definerPCONP

9、(*(volatileunsigned*)(0x400FC0C4)#definerU2LCR(*(volatileunsigned*)(0x4009800C)#definerU2FDR#definerU2DLL#definerU2DLM#definerU2TER#definerU2THR#definerU2RBR#definerU2FCR#definerU2IIR#definerU2LSR#definerU2IER#definerU2ACR(*(volatileunsigned*)(0x40098028)(*(volatileunsigned*)(0x40098000)(*(volatileu

10、nsigned*)(0x40098004)(*(volatileunsigned*)(0x40098030)(*(volatileunsigned*)(0x40098000)(*(volatileunsigned*)(0x40098000)(*(volatileunsigned*)(0x40098008)(*(volatileunsigned*)(0x40098008)(*(volatileunsigned*)(0x40098014)(*(volatileunsigned*)(0x40098004)(*(volatileunsigned*)(0x40098020)voidUART2_IRQHa

11、ndler()unsignedintintId;chartmp_char;intId=rU2IIR&0xf;rU2THR=intId;/RDA或者CTI中斷if(intId=0xc|intId=0x4)/DLAB=0rU2LCR&=(0x1<<7);tmp_char=rU2RBR&0xff;rU2THR=tmp_char;intId=rU2IIR&0xf;rU2THR=intId;if(tmp_char=0xa5)rFIOIPIN|=(1<<18);elseif(tmp_char=0x5a)rFIO1PIN&=(1<<

12、18);voidSystemInit()rSCS&=(0x1<<4);/頻率12MrSCS|=(0x1<<5);/使能主振蕩器while(0=(rSCS&(0x1<<6);/等待主振蕩器穩定rCLKSRCSEL=0x1;rPLL0CFG=0x9;/配置CCLK=120MrPLL0CON=0x01;rPLL0FEED=0xAA;rPLL0FEED=0x55;while(0=(rPLL0STAT&(0x1<<10);rCCLKSEL=(0x1|(0x1<<8);rPCLKSEL=0x2;/配置PCLK=60MrCL

13、KOUTCFG=0x0|(0xb<<4)|(0x1<<8);voidInit_Uart2()rPCONP|=0x1<<24;/使能UART2功率控制rIOCON_P0_10=(rIOCON_P0_10&(0x7)|0x1;/P0.10P0.11做UART2的發送和接收管腳rIOCON_P0_11=(rIOCON_P0_11&(0x7)|0x1;rU2LCR|=0x1<<7;/DLAB=1rU2FDR=1|2<<4;/波特率設置115200/等待rU2THR中的數據發送完成，防止rU2DLM=0;rU2DLL=22;rU

14、2LCR&=(0x1<<7);rU2LCR|=0x3;rU2TER|=0x1<<7;rU2IER|=0x1;rU2FCR|=0x1;rU2FCR|=0x1<<1|0x1<<2;rISER0|=0x1<<7;voidUart2SendC(charc)rU2THR=c&0xff;while(!(rU2LSR&(0x1<<5);數據溢出/DLAB=0/8位數據位，無校驗，1個停止位/使能串口2的發送/使能串口2的接收中斷/復位FIFO,設置接收1個字符觸發中斷/使能串口2中斷voidUart2SendS(char*s)(while(*s)(Uart2SendC(*s);s+；intmain(void)(charstr="nr1,DisplaytheU2IIR3:0+Data+U2IIR3:0nr2,Send0x5a->TurnontheLEDnr3,Send0xa5->TurnofftheLEDnr"rFI