TQ2440裸机上的UART程序分析

此程序是从天嵌提供的测试程序中裁剪出来的，这样看起来会比较简洁

程序到这边下载：http://download.csdn.net/detail/lufeiop02/4127780

一，首先是主程序：

int Main ()
{
U8 key;
U32 mpll_val = 0;

Port_Init(); //端口初始化

key = 14;     //这5行是关于cpu频率的设置，可以看另一篇文章：
mpll_val = (92<<12)|(1<<4)|(1);
ChangeMPllValue((mpll_val>>12)&0xff, (mpll_val>>4)&0x3f, mpll_val&3);
ChangeClockDivider(key, 12);
cal_cpu_bus_clk();
//这一段代码，选择了串口波特率为 115200。
consoleNum = 0; //  s3c2440有三个UART,这里选择UART0
Uart_Init( 0,115200 ); //初始化UART
Uart_Select( consoleNum ); //选择UART0
Uart_Printf(" TQ2440 Test Program\n"); //打印字符串，一般就是用这个函数来打印一些信息
return 0;
}

下面这一大堆函数就是2440lib.c文件中关于UART 的所有函数，当然我们一般只用到其中小部分，我尽量都分析一下

//***************************[ UART ]******************************
static int whichUart=0;

void Uart_Init(int pclk,int baud)
{
int i;
if(pclk == 0)
pclk = PCLK; //如果参数为0，就用系统的PCLK,这个PCLK就APH设备所有的时钟频率，APH设备是指那些比较低速的外围设备

rUFCON0 = 0x0;   //UART channel 0 FIFO control register, FIFO disable
rUFCON1 = 0x0;   //UART channel 1 FIFO control register, FIFO disable
rUFCON2 = 0x0;   //UART channel 2 FIFO control register, FIFO disable
rUMCON0 = 0x0;   //UART chaneel 0 MODEM control register, AFC disable
rUMCON1 = 0x0;   //UART chaneel 1 MODEM control register, AFC disable

//UART0               这个三个串口的配置都是一样的
rULCON0 = 0x3;   //Line control register : Normal,No parity,1 stop,8 bits
//配置功能列表
// [10]       [9]    [8]     [7]        [6]     [5]         [4]    [3:2]        [1:0]
// Clock Sel,Tx Int,Rx Int,Rx Time Out,Rx err,Loop-back,Send break,Transmit Mode,Receive Mode
//     0        1      0    ,   0         1       0           0     , 01          01
//   PCLK     Level  Pulse    Disable  Generate  Normal     Normal    Interrupt or Polling
rUCON0  = 0x245;
//Control register 这个寄存器有16位需要配置，12-15位为零，所以禁止FCLK/n时钟(这里可以不理会) 11-10位如下图所示

所以只要第10位为0就选择PCLK给UART波特率
rUBRDIV0=( (int)(pclk/16./baud+0.5) -1 );   //Baud rate divisior register 0 这句话也对应着上图
下图是对上面 《配置功能列表》的详细说明吧

//UART1
rULCON1 = 0x3;
rUCON1  = 0x245;
rUBRDIV1=( (int)(pclk/16./baud+0.5) -1 );
//UART2
rULCON2 = 0x3;
rUCON2  = 0x245;
rUBRDIV2=( (int)(pclk/16./baud+0.5) -1 );
for(i=0;i<100;i++);}
//关于rUBRDIV可以再看看下图

//===================================================================
void Uart_Select(int ch)  //s3c2440有三个UART,这个函数用来指定用哪个UART
{
whichUart = ch;
}
//=====================================================================
//If you don't use vsprintf(), the code size is reduced very much.
void Uart_Printf(char *fmt,...)  //这个函数用到了可变参数，详细分析请看这篇文章：

Uart_Printf()函数学习报告

{
va_list ap;
char string[256];
va_start(ap,fmt);
vsprintf(string,fmt,ap); //简单来说，上面这四行代码把参数中的那些字符串都整合在了string数组里了
Uart_SendString(string); //string里其实就是我们要打印到串口的内容了
va_end(ap);
}
//====================================================================
void Uart_SendString(char *pt)  //打印pt指向的字符串
{
while(*pt) //化整为零，逐个字符打印
Uart_SendByte(*pt++); //以字节为单位打印，对应ULCON中设置的“每帧用于发送或接收的数据位的个数”（8位）
}
//=====================================================================
void Uart_SendByte(int data) //重头戏来了，这个函数就是真正在发送数据了
{               //这边的三个分支对应三个UART

if(whichUart==0) //我们执行的是这个分支{if(data=='\n')//因为在WIN下,'\n'表示回车,换行两个意思,而在别的系统下,它只表示回车,所以最后得给它来个换行,也就是:
'\r '

{ //遇到'\n'时，实际发送的是'\r\n'
while(!(rUTRSTAT0 & 0x2));
// Delay(1);                 //because the slow response of hyper_terminal
WrUTXH0('\r');
}

//下图为UTRSTAT寄存器第1位的功能描述

while(!(rUTRSTAT0 & 0x2));   //Wait until THR is empty. 等待发送缓冲器空
//  Delay(1);
WrUTXH0(data);//2440addr.h中：#define WrUTXH0(ch) (*(volatile unsigned char *)0x50000020)=(unsigned char)(ch)

}
else if(whichUart==1)  //同上
{
if(data=='\n')
{
while(!(rUTRSTAT1 & 0x2));
//Delay(1);                 //because the slow response of hyper_terminal
rUTXH1 = '\r';
}
while(!(rUTRSTAT1 & 0x2));   //Wait until THR is empty.
//Delay(1);
rUTXH1 = data;
}
else if(whichUart==2) //同上
{
if(data=='\n')
{
while(!(rUTRSTAT2 & 0x2));
//Delay(1);                 //because the slow response of hyper_terminal
rUTXH2 = '\r';
}
while(!(rUTRSTAT2 & 0x2));   //Wait until THR is empty.
//Delay(1);
rUTXH2 = data;
}
}

//===================================================================void Uart_TxEmpty(int ch) //判断发送移位寄存器是否为空{

if(ch==0)
while(!(rUTRSTAT0 & 0x4)); //Wait until tx shifter is empty.

else if(ch==1)
while(!(rUTRSTAT1 & 0x4)); //Wait until tx shifter is empty.

else if(ch==2)
while(!(rUTRSTAT2 & 0x4)); //Wait until tx shifter is empty.
}

***********************************************************************

上面是有关发送的函数，下面是有关接收的函数，待以后分析

//=====================================================================
char Uart_Getch(void)
{
if(whichUart==0)
{
while(!(rUTRSTAT0 & 0x1)); //Receive data ready
return RdURXH0();
}
else if(whichUart==1)
{
while(!(rUTRSTAT1 & 0x1)); //Receive data ready
return RdURXH1();
}
else if(whichUart==2)
{
while(!(rUTRSTAT2 & 0x1)); //Receive data ready
return RdURXH2();
}

return 0 ;
}

//====================================================================
char Uart_GetKey(void)
{
if(whichUart==0)
{
if(rUTRSTAT0 & 0x1)    //Receive data ready
return RdURXH0();
else
return 0;
}
else if(whichUart==1)
{
if(rUTRSTAT1 & 0x1)    //Receive data ready
return RdURXH1();
else
return 0;
}
else if(whichUart==2)
{
if(rUTRSTAT2 & 0x1)    //Receive data ready
return RdURXH2();
else
return 0;
}

return 0 ;
}

//====================================================================
void Uart_GetString(char *string)
{
char *string2 = string;
char c;
while((c = Uart_Getch())!='\r')
{
if(c=='\b')
{
if( (int)string2 < (int)string )
{
Uart_Printf("\b \b");
string--;
}
}
else
{
*string++ = c;
Uart_SendByte(c);
}
}
*string='\0';
Uart_SendByte('\n');
}

//=====================================================================
int Uart_GetIntNum(void)
{
char str[30];
char *string = str;
int base     = 10;
int minus    = 0;
int result   = 0;
int lastIndex;
int i;

Uart_GetString(string);

if(string[0]=='-')
{
minus = 1;
string++;
}

if(string[0]=='0' && (string[1]=='x' || string[1]=='X'))
{
base    = 16;
string += 2;
}

lastIndex = strlen(string) - 1;

if(lastIndex<0)
return -1;

if(string[lastIndex]=='h' || string[lastIndex]=='H' )
{
base = 16;
string[lastIndex] = 0;
lastIndex--;
}

if(base==10)
{
result = atoi(string);
result = minus ? (-1*result):result;
}
else
{
for(i=0;i<=lastIndex;i++)
{
if(isalpha(string[i]))
{
if(isupper(string[i]))
result = (result<<4) + string[i] - 'A' + 10;
else
result = (result<<4) + string[i] - 'a' + 10;
}
else
result = (result<<4) + string[i] - '0';
}
result = minus ? (-1*result):result;
}
return result;
}

//*****************************************************************************
//get a number for the uart
//*****************************************************************************
int Uart_GetIntNum_GJ(void)
{
char string[16] ;
char *p_string = string ;
char c;
int i = 0 ;
int data = 0 ;

while(   ( c = Uart_Getch()) != '\r'  )
{
if(c=='\b')		p_string--;
else		*p_string++=c;

Uart_SendByte( c ) ;
}

*p_string = '\0';

i = 0 ;
while( string[i] != '\0' )
{
data = data * 10 ;
if( string[i]<'0'||string[i]>'9' )
return -1 ;
data = data + ( string[i]-'0' ) ;
i++ ;
}

return data ;
}
//*****************************************************************************