S3C2440 UART串口驅(qū)動

;輪詢方式實現(xiàn)數(shù)據(jù)發(fā)送偽代碼
Send(){
While(1){
if(發(fā)送狀態(tài)==可發(fā)送)
執(zhí)行數(shù)據(jù)發(fā)送操作;
}
}

;輪詢方式實現(xiàn)數(shù)據(jù)接收偽代碼
Receive(){
While(1){
if(接收狀態(tài)==有數(shù)據(jù)到達)
執(zhí)行數(shù)據(jù)接收操作;
}
}

UART除數(shù)（UBRDIVn）= (int)(CLK/(buad rate * 16 )) - 1

UBRDIVn = (int)(50M / (115200 x 16)) - 1 = 26

UBRDIVn = (int)(12M / (57600 x 16)) - 1 = 12

UART Error = (tUPCLK - tUEXACT)/ tUEXACT * 100%

tUPCLK = 27 * 16 * 10 / 50M = 0.0000864
tUEXACT = 10 / 115200 = 0.0000868
UART Error= | 0.0000864 - 0.0000868 | / 0.0000868 = 0.46%

tUPCLK = 7 * 16 * 10 / 12M = 0.0000933
tUEXACT = 10 / 115200 = 0.0000868
UART Error = | 0.0000933 - 0.0000868 | / 0.0000868 = 7.5%

UBRDIVn = (int)(12M / (57600 * 16)) - 1 = 12
tUPCLK = 13 * 16 * 10 / 12M = 0.000173
tUEXACT = 10 / 57600 = 0.0001736
UART Error = | 0. 000173 - 0. 0001736 | / 0. 0001736 = 0.345%

GPHCON | = 0xa0;

GPHUP = 0x0;

ULCON0 = 0x03;

UCON0 = 0x05;

UFCON0 = 0x00;//不使用FIFO
UMCON0 = 0x00;//不使用流控
UBRDIV0 = 26;//波特率為115200,PCLK=50Mhz
UBRDIV0 = 53;//波特率為57600,PCLK=50Mhz
UBRDIV0 = 12;//波特率為57600,PCLK=12Mhz

#defineTXD0READY(1<<2)//發(fā)送數(shù)據(jù)狀態(tài)OK
#defineRXD0READY(1)//接收數(shù)據(jù)狀態(tài)OK

/* UART串口單個字符打印函數(shù)*/
extern void putc(unsigned char c)
{
while( ! (UTRSTAT0 & TXD0READY) );
UTXH0 = c;
}

/* UART串口接受單個字符函數(shù)*/
extern unsigned char getc(void)
{
while( ! (UTRSTAT0 & RXD0READY) );
return URXH0;
}

;
; UART串口實驗
;

GPBCONEQU0x56000010
GPBDATEQU0x56000014
AREA Init, CODE, READONLY
ENTRY
start
; close watchdog
ldr r0, = 0x53000000;將看門狗控制寄存器地址放入r0
mov r1, #0
str r1, [r0];設(shè)置看門狗控制寄存器的值為0

bl initmem;跳轉(zhuǎn)到initmem代碼段，初始化內(nèi)存

IMPORT xmain;引入main.c中的xmain函數(shù)
ldr sp, =0x34000000;調(diào)用C程序之前先初始化棧指針
ldr lr, =loop;設(shè)置xmain函數(shù)的返回地址
ldr pc, =xmain;跳轉(zhuǎn)到C程序中的xmain函數(shù)的入口處執(zhí)行

loop
b loop;死循環(huán)

initmem;內(nèi)存初始化
ldr r0, =0x48000000;加載內(nèi)存相關(guān)寄存器首地址r0
ldr r1, =0x48000034;加載內(nèi)存相關(guān)寄存器尾地址到r1
adr r2, memdata;將寄存器配置數(shù)據(jù)地址段首地址加載到r2
initmemloop
ldr r3, [r2], #4;循環(huán)設(shè)置存寄存器
str r3, [r0], #4
teq r0, r1
bne initmemloop;循環(huán)到最后一個寄存器時退出函數(shù)
mov pc,lr

memdata
DCD0x22000000;BWSCON
DCD0x00000700;BANKCON0
DCD0x00000700;BANKCON1
DCD0x00000700;BANKCON2
DCD0x00000700;BANKCON3
DCD0x00000700;BANKCON4
DCD0x00000700;BANKCON5
DCD0x00018005;BANKCON6
DCD0x00018005;BANKCON7
DCD0x008e07a3;REFRESH
DCD0x000000b1;BANKSIZE
DCD0x00000030;MRSRB6
DCD0x00000030;MRSRB7

END

/* xmain.c */

/* GPIO registers */
#defineGPHCON(*(volatile unsigned long *)0x56000070)
#defineGPHDAT(*(volatile unsigned long *)0x56000074)
#defineGPHUP(*(volatile unsigned long *)0x56000078)

/*UART registers*/
#defineULCON0(*(volatile unsigned long *)0x50000000)
#defineUCON0(*(volatile unsigned long *)0x50000004)
#defineUFCON0(*(volatile unsigned long *)0x50000008)
#defineUMCON0(*(volatile unsigned long *)0x5000000c)
#defineUTRSTAT0(*(volatile unsigned long *)0x50000010)
#defineUTXH0(*(volatile unsigned char *)0x50000020)
#defineURXH0(*(volatile unsigned char *)0x50000024)
#defineUBRDIV0(*(volatile unsigned long *)0x50000028)

#defineTXD0READY(1<<2)//發(fā)送數(shù)據(jù)狀態(tài)OK
#defineRXD0READY(1)//接收數(shù)據(jù)狀態(tài)OK

/* UART串口初始化*/
void uart_init( )
{
GPHCON |= 0xa0;//GPH2,GPH3 used as TXD0,RXD0
GPHUP= 0x0;//GPH2,GPH3內(nèi)部上拉
ULCON0= 0x03;//8N1
UCON0= 0x05;//查詢方式為輪詢或中斷;時鐘選擇為PCLK
UFCON0 = 0x00;//不使用FIFO
UMCON0 = 0x00;//不使用流控
UBRDIV0 = 12;//波特率為57600,PCLK=12Mhz
}

/* UART串口單個字符打印函數(shù)*/
extern void putc(unsigned char c)
{
while( ! (UTRSTAT0 & TXD0READY) );
UTXH0 = c;
}

/* UART串口接受單個字符函數(shù)*/
extern unsigned char getc(void)
{
while( ! (UTRSTAT0 & RXD0READY) );
return URXH0;
}

/* UART串口字符串打印函數(shù)*/
extern int printk(const char* str)
{
int i = 0;
while( str[i] ){
putc( (unsigned char) str[i++] );
}
return i;
}

__inline void delay(int msec)
{
int i, j;
for(i = 1000; i > 0; i--)
for(j = msec*10; j > 0; j--)
/* do nothing */;
}

/* xmain通過UART串口打印字符串*/
int xmain()
{
uart_init();
while(1) {
delay(10);
printk("Uart串口打印試驗/r/n");
}
return 0;
}