Cortex-M3学习日志（四）-- UART0实验

LPC1768含有4 个符合16C550工业标准的异步串口UATR0-UART3，其中UART1具有标准的MODEM接口和RS232。至于RS232的标准是什么样的，这里不在总结了，如果哪位有兴趣可以上网查一下维基百科。RS-485是后期出现的一个传输标准，关于它们的特性，下面列表总结一下：

RS-232特性	RS-485特性
最高速率约为20kb/s	与TTL电平兼容
传输最大距离约为15m	传输距离实际达1200m
共模抑制比能力差	共模抑制比能力强

UATR0/2/3可以工作在UART模式下，也可以工作在IrDA模式下， IrDA是红外数据组织（Infrared Data Association）的简称，目前广泛采用的IrDA红外连接技术就是由该组织提出的。到目前为止，全球采用IrDA技术的设备超过了5000万部。IrDA已经制订出物理介质和 协议层规格，以及2个支持IrDA标准的设备可以相互监测对方并交换数据。 初始的IrDA1.0 标准制订了一个串行，半双工的同步系统，传输速率为2400bps到115200bps，传输范围1 m，传输半角度为15度到30度。最近IrDA扩展了其物理层规格使数据传输率提升到4Mbps。IrDA数据协议由物理层，链路接入层和链路管理层三个基本层协议组成，另外，为满足各层上的应用的需要，IrDA栈支持IrLAP, IrLMP, IrIAS, IrIAP, IrLPT, IrCOMM, IrOBEX和IrLAN等。IrDA的优点是成本低，体积小、功耗低，数据传输干扰小等。关于IrDA的协议与应用这里暂时先不总结，后续学习中会再慢慢涉及到，届时将做深入研究。UATR1具有MODEM接口，能过该接口可以接入电话网络，实现远距离通讯。至于怎么通讯，这里也暂时不总结，因为这一块懒猫也没有深入研究。

关于串口的配置主要涉及到引脚的配置，波特率的配置，帧格式的设置及FIFO设置等。涉及到的寄存器主要有接收缓冲寄存器，它包含即将读取的接收数据。发送保持寄存器，它主要是用来写入发送数据的，中断使能寄存器IER，若是用到中断接收或发送时需配置些寄存器，与之相关联的寄存器还有中断标志寄存器IIR。还有FIFO控制寄存器FCR，它是用来配置先进先出相关的东东的。线控制寄存器LCR，这个寄存器主要就是用来设置帧格式的，与这个寄存器相关联的寄存器是线状态寄存器LSR，用来读取帧格式状态的寄存器。当然还有缓存寄存器SCR，这个与串口操作关系不大。还有自动波特率控制器ACR，配置程序自适应波特率的。还有IrDA控制寄存器，它与红外发送与接收有关。小数分频寄存器FDR，它是波特率配置有关。传输使能寄存器TER，如果这个寄存器的TXEN配置为1，刚只要缓存中有有效数据，就可以通过发送引脚把数据发送出去。还有一个寄存器FIFO等级寄存器FIFOLVL，它是个只读寄存器，用来读取当前FIFO等级状态。此次实验我是用查询方式发送字符到串口，所以很大寄存器没有用到，关于寄存器的详细说明可以参考LPC1768的数据手册，这里就不再照搬手册了。下面简单说一下这次实验电路图，主要是一个 按键，8个LED灯，还有串口0，功能就是按一下按键亮一个灯，等全亮时，再按按键灯全来，然后再按按键时第按一下点亮一个，循环往复，同时哪个灯亮，就发送字符“Led  X  on”，下面是这次实验的电路图：

                                      图 1-1 实验电路图

下面简单说一下这个软件，软件主要分为两大部分，一个是关于串口配置及常用的函数，另一个就是主LED点灯程序，分别在UART.C与MAIN.C两个源文件中，下面把部分代码帖出来，完整部分请参阅附件：

（1）、 uart.c源文件

#include "includes.h"

 

void UARTInit( uint32_t PortNum, uint32_t baudrate )

{

  uint32_t Fdiv;

 

  if ( PortNum == 0 )

  {

    PINCON->PINSEL0 |= (1 << 4);             

    PINCON->PINSEL0 |= (1 << 6);             

 

            UART0->LCR  = 0x83;                       

    Fdiv = (SystemFrequency/4/ 16) / baudrate;

    UART0->DLM  = Fdiv / 256;

    UART0->DLL  = Fdiv % 256+1;

    UART0->LCR  = 0x03;                       

    UART0->FCR  = 0x07;                       

 

  }

  else if ( PortNum == 1 )

  {

               PINCON->PINSEL4 |= (1<<1);                

          PINCON->PINSEL4 |= (1<<3);                

   

               UART1->LCR = 0x83;                                  

    Fdiv = (SystemFrequency/4/16)/ baudrate ;

    UART1->DLM = Fdiv/256;                                                                                             

    UART1->DLL = (Fdiv%6)+1;

               UART1->LCR = 0x03;                                   

    UART1->FCR = 0x07;                             

 

  }

}

 

 

void UARTSend( uint32_t portNum, uint8_t *BufferPtr, uint32_t Length )

{

  if ( portNum == 0 )

  {

    while ( Length != 0 )

    {

                 while ( !(UART0->LSR & 0x20) );   

                 UART0->THR = *BufferPtr;           

                 BufferPtr++;                       

                 Length--;                          

               }

  }

  else

  {

               while ( Length != 0 )

    {

                 while ( !(UART1->LSR & 0x20));    

                 UART1->THR = *BufferPtr;                                         

                 BufferPtr++;                                                                                  

                 Length--;                                                                                         

    }

  }

  return;

}

 

int UART0_SendByte (int ucData)

{

               while (!(UART0->LSR & 0x20));

    return (UART0->THR = ucData);

}

 

void UART0_SendString (unsigned char *s)

{

            while (*s != '\0')

               {

                        UART0_SendByte(*s++);

               }

}

（2）、 main.c源文件

#include"includes.h"

                                                                                                                                  

volatile unsigned long SysTickCnt;                   

unsigned char LedOnMeg[] = "Led 1 On!\r\n";

unsigned char LedOffMeg[] = "Led all Off!\r\n";

unsigned char KeyMeg[] = "key push down \r\n";

unsigned char OpenString[][50] = {

                                "**********************************************\r\n",

                                "****             --欢迎光临--             ****\r\n",

                                                                                                                 "**** 小野兽的小草窝^_^                    ****\r\n",

                                                                                                                 "**** http://blog.ednchina.com/ytfdhb/     ****\r\n",

                                                                                                                 "**** 我是懒猫爱飞，我的口号是：           ****\r\n",

                                                                                                                 "**** 每天进步一点点，开心多一点^_^        ****\r\n",

                                                                                                                 "**********************************************\r\n"

                                                                                                       };

 

unsigned int key_sta = 0;              

unsigned int key_pre = 1;                 

unsigned int key_old = 1;                                      

unsigned int led_flag = 0;

 

unsigned int  StepCnt = 0;        

 

 

void SysTick_Handler (void)

{         

  SysTickCnt++;

}

 

 

void DelayMs (unsigned long tick)

{     

  unsigned long systickcnt;

 

  systickcnt = SysTickCnt;

 

  while ((SysTickCnt - systickcnt) < tick);

}

 

void PortInit(void)

{

   GPIO1->FIODIR = 0xB0000000;           

   GPIO2->FIODIR = 0x0000007C;           

   LedAllOff();                                                                                                

}

 

 

void KeyScan()

{

               key_pre = KEY_EN ;

               if(!KEY_EN )                      

               {

                             if(key_old)

                             {

                                 if(key_pre == 0)         

                                 {

                                            key_sta = 1;            

                                 }  

                   }

               }

               key_old = key_pre;

}

 

 

void KeyHandle(void)

{

    if(key_sta == 1)

    {

                   StepCnt++;                        

                             if(StepCnt == 9)

                             {

                                           UART0_SendString (LedOffMeg);                   

                             }

                              if(StepCnt < 9)

                             {

                                           LedOnMeg[4] = StepCnt+0x30;       

                 UART0_SendString (LedOnMeg);                                       

                             }

                             key_sta = 0;                     

               }            

}

void LedHandle()

{

               switch(StepCnt)

               {

                             case 1:Led1On();   

                                    break;

                             case 2:Led2On();   

                                    break;

                   case 3:Led3On();   

                                    break;

                   case 4:Led4On();   

                                    break;

                             case 5:Led5On();   

                                    break;

                             case 6:Led6On();   

                                    break;

                             case 7:Led7On();   

                                    break;

                             case 8:Led8On();   

                                    break;

                   case 9:LedAllOff();         

                                    StepCnt = 0;               

                                    break;

 

                             default:break;

               }

}

 

 

int main(void)

{

    unsigned int i = 0;

 

               SystemInit();       

               SysTick_Config(SystemFrequency/1000 - 1);

                                                      

    PortInit();                              

 

               UARTInit(0,19200);                         

               for(i=0;i<7;i++)

               {

                             UARTSend(0,OpenString[i],50);           

               }

 

//LedOnMeg[4] = 4+0x30;                    

//UART0_SendString (KeyMeg);

 

               while(1)

               {

                 KeyScan();   // 按键扫描

 

                 KeyHandle(); // 按键处理

 

                 LedHandle(); // Led处理程序

               }

}

程序不是太难，只是简单的实验，各个部分都有详细的注释，这里不在总结，下面是挨靠结果串口调试助手截图：

图 1-2 串口助手截图

好了，先总结到这吧，最近手头上的事有点多，所以写日志的时间就有点紧张，不过，工作归工作，该学习的东东还是要坚持学习的，没有足够的时间，那就见缝插针的学吧。