实验(11)、UART操作
一、编写使用按键中断程序
1、程序功能：在串口上输入一个字符，单板接收到后将它的ASCII值加1后，从串口输出。
2、写程序如下：head.S、init.c、serial.c、main.c、s3c24xx.h、serial.h、makefile、uart.lds
（1）head.S程序如下：
@******************************************************************************
@ File：head.S
@功能：设置SDRAM，将程序复制到SDRAM，然后跳到SDRAM继续执行
@******************************************************************************
.extern main
.text
.global _start
_start:
Reset:
ldr sp, =4096 @设置栈指针，以下都是C函数，调用前需要设好栈
bl disable_watch_dog @关闭WATCHDOG，否则CPU会不断重启
bl clock_init @设置MPLL，改变FCLK、HCLK、PCLK
bl memsetup @设置存储控制器以使用SDRAM
bl copy_steppingstone_to_sdram @复制代码到SDRAM中
ldr pc, =on_sdram @跳到SDRAM中继续执行
on_sdram:
ldr sp, =0x34000000 @设置栈指针，
ldr lr, =halt_loop @设置返回地址
ldr pc, =main @调用main函数
halt_loop:
b halt_loop
（2）init.c程序如下：
/*
* init.c:进行一些初始化
*/
#include "s3c24xx.h"
void disable_watch_dog(void);
void clock_init(void);
void memsetup(void);
void copy_steppingstone_to_sdram(void);
/*
*关闭WATCHDOG，否则CPU会不断重启
*/
void disable_watch_dog(void)
{
WTCON = 0; //关闭WATCHDOG很简单，往这个寄存器写0即可
}
#define S3C2410_MPLL_200MHZ ((0x5c<<12)|(0x04<<4)|(0x00))
#define S3C2440_MPLL_200MHZ ((0x5c<<12)|(0x01<<4)|(0x02))
/*
*对于MPLLCON寄存器，[19:12]为MDIV，[9:4]为PDIV，[1:0]为SDIV
*有如下计算公式：
* S3C2410: MPLL(FCLK) = (m * Fin)/(p * 2^s)
* S3C2410: MPLL(FCLK) = (2 * m * Fin)/(p * 2^s)
*其中: m = MDIV + 8, p = PDIV + 2, s = SDIV
*对于本开发板，Fin = 12MHz
*设置CLKDIVN，令分频比为：FCLK:HCLK:PCLK=1:2:4，
* FCLK=200MHz,HCLK=100MHz,PCLK=50MHz
*/
void clock_init(void)
{
// LOCKTIME = 0x00ffffff; //使用默认值即可
CLKDIVN = 0x03; // FCLK:HCLK:PCLK=1:2:4, HDIVN=1,PDIVN=1
/*如果HDIVN非0，CPU的总线模式应该从“fast bus mode”变为“asynchronous bus mode”*/
__asm__(
"mrc p15, 0, r1, c1, c0, 0\n" /*读出控制寄存器*/
"orr r1, r1, #0xc0000000\n" /*设置为“asynchronous bus mode”*/
"mcr p15, 0, r1, c1, c0, 0\n" /*写入控制寄存器*/
);
/*判断是S3C2410还是S3C2440 */
if ((GSTATUS1 == 0x32410000) || (GSTATUS1 == 0x32410002))
{
MPLLCON = S3C2410_MPLL_200MHZ; /*现在，FCLK=200M,HCLK=100M,PCLK=50M*/
}
else
{
MPLLCON = S3C2440_MPLL_200MHZ; /*现在，FCLK=200M,HCLK=100M,PCLK=50M*/
}
}
/*
*设置存储控制器以使用SDRAM
*/
void memsetup(void)
{
volatile unsigned long *p = (volatile unsigned long *)MEM_CTL_BASE;
/*这个函数之所以这样赋值，而不是像前面的实验(比如mmu实验)那样将配置值
*写在数组中，是因为要生成”位置无关的代码”，使得这个函数可以在被复制到
* SDRAM之前就可以在steppingstone中运行
*/
/*存储控制器13个寄存器的值*/
p[0] = 0x22011110; //BWSCON
p[1] = 0x00000700; //BANKCON0
p[2] = 0x00000700; //BANKCON1
p[3] = 0x00000700; //BANKCON2
p[4] = 0x00000700; //BANKCON3
p[5] = 0x00000700; //BANKCON4
p[6] = 0x00000700; //BANKCON5
p[7] = 0x00018005; //BANKCON6
p[8] = 0x00018005; //BANKCON7
/* REFRESH,
* HCLK=12MHz: 0x008C07A3,
* HCLK=100MHz: 0x008C04F4
*/
p[9] = 0x008C04F4;
p[10] = 0x000000B1; //BANKSIZE
p[11] = 0x00000030; //MRSRB6
p[12] = 0x00000030; //MRSRB7
}
void copy_steppingstone_to_sdram(void)
{
unsigned int *pdwSrc = (unsigned int *)0;
unsigned int *pdwDest = (unsigned int *)0x30000000;
while (pdwSrc < (unsigned int *)4096)
{
*pdwDest = *pdwSrc;
pdwDest++;
pdwSrc++;
}
}
（3）serial.c程序如下：
#include "s3c24xx.h"
#include "serial.h"
#define TXD0READY (1<<2)
#define RXD0READY (1)
#define PCLK 50000000 // init.c中的clock_init函数设置PCLK为50MHz
#define UART_CLK PCLK // UART0的时钟源设为PCLK
#define UART_BAUD_RATE 115200 //波特率
#define UART_BRD ((UART_CLK / (UART_BAUD_RATE * 16)) - 1)
/*
*初始化UART0，115200,8N1,无流控
*/
void uart0_init(void)
{
GPHCON |= 0xa0; // GPH2,GPH3用作TXD0,RXD0
GPHUP = 0x0c; // GPH2,GPH3内部上拉
ULCON0 = 0x03; // 8N1(8个数据位，无较验，1个停止位)
UCON0 = 0x05; //查询方式，UART时钟源为PCLK
UFCON0 = 0x00; //不使用FIFO
UMCON0 = 0x00; //不使用流控
UBRDIV0 = UART_BRD; //波特率为115200
}
/*
*发送一个字符
*/
void putc(unsigned char c)
{
/*等待，直到发送缓冲区中的数据已经全部发送出去*/
while (!(UTRSTAT0 & TXD0READY));
/*向UTXH0寄存器中写入数据，UART即自动将它发送出去*/
UTXH0 = c;
}
/*
*接收字符
*/
unsigned char getc(void)
{
/*等待，直到接收缓冲区中的有数据*/
while (!(UTRSTAT0 & RXD0READY));
/*直接读取URXH0寄存器，即可获得接收到的数据*/
return URXH0;
}
/*
*判断一个字符是否数字
*/
int isDigit(unsigned char c)
{
if (c >= '0' && c <= '9')
return 1;
else
return 0;
}
/*
*判断一个字符是否英文字母
*/
int isLetter(unsigned char c)
{
if (c >= 'a' && c <= 'z')
return 1;
else if (c >= 'A' && c <= 'Z')
return 1;
else
return 0;
}
（4）main.c程序如下：
#include "serial.h"
int main()
{
unsigned char c;
uart0_init(); //波特率115200，8N1(8个数据位，无校验位，1个停止位)
while(1){
//从串口接收数据后，判断其是否数字或子母，若是则加1后输出
c = getc();
if (isDigit(c) || isLetter(c))
putc(c+1);
}
return 0;
}
（5）s3c24xx.h程序如下：
/* WOTCH DOG register */
#define WTCON (*(volatile unsigned long *)0x53000000)
/* SDRAM regisers */
#define MEM_CTL_BASE 0x48000000
#define SDRAM_BASE 0x30000000
/* NAND Flash registers */
#define NFCONF (*(volatile unsigned int *)0x4e000000)
#define NFCMD (*(volatile unsigned char *)0x4e000004)
#define NFADDR (*(volatile unsigned char *)0x4e000008)
#define NFDATA (*(volatile unsigned char *)0x4e00000c)
#define NFSTAT (*(volatile unsigned char *)0x4e000010)
/*GPIO registers*/
#define GPBCON (*(volatile unsigned long *)0x56000010)
#define GPBDAT (*(volatile unsigned long *)0x56000014)
#define GPFCON (*(volatile unsigned long *)0x56000050)
#define GPFDAT (*(volatile unsigned long *)0x56000054)
#define GPFUP (*(volatile unsigned long *)0x56000058)
#define GPGCON (*(volatile unsigned long *)0x56000060)
#define GPGDAT (*(volatile unsigned long *)0x56000064)
#define GPGUP (*(volatile unsigned long *)0x56000068)
#define GPHCON (*(volatile unsigned long *)0x56000070)
#define GPHDAT (*(volatile unsigned long *)0x56000074)
#define GPHUP (*(volatile unsigned long *)0x56000078)
/*UART registers*/
#define ULCON0 (*(volatile unsigned long *)0x50000000)
#define UCON0 (*(volatile unsigned long *)0x50000004)
#define UFCON0 (*(volatile unsigned long *)0x50000008)
#define UMCON0 (*(volatile unsigned long *)0x5000000c)
#define UTRSTAT0 (*(volatile unsigned long *)0x50000010)
#define UTXH0 (*(volatile unsigned char *)0x50000020)
#define URXH0 (*(volatile unsigned char *)0x50000024)
#define UBRDIV0 (*(volatile unsigned long *)0x50000028)
/*interrupt registes*/
#define SRCPND (*(volatile unsigned long *)0x4A000000)
#define INTMOD (*(volatile unsigned long *)0x4A000004)
#define INTMSK (*(volatile unsigned long *)0x4A000008)
#define PRIORITY (*(volatile unsigned long *)0x4A00000c)
#define INTPND (*(volatile unsigned long *)0x4A000010)
#define INTOFFSET (*(volatile unsigned long *)0x4A000014)
#define SUBSRCPND (*(volatile unsigned long *)0x4A000018)
#define INTSUBMSK (*(volatile unsigned long *)0x4A00001c)
/*external interrupt registers*/
#define EINTMASK (*(volatile unsigned long *)0x560000a4)
#define EINTPEND (*(volatile unsigned long *)0x560000a8)
/*clock registers*/
#define LOCKTIME (*(volatile unsigned long *)0x4c000000)
#define MPLLCON (*(volatile unsigned long *)0x4c000004)
#define UPLLCON (*(volatile unsigned long *)0x4c000008)
#define CLKCON (*(volatile unsigned long *)0x4c00000c)
#define CLKSLOW (*(volatile unsigned long *)0x4c000010)
#define CLKDIVN (*(volatile unsigned long *)0x4c000014)
/*PWM & Timer registers*/
#define TCFG0 (*(volatile unsigned long *)0x51000000)
#define TCFG1 (*(volatile unsigned long *)0x51000004)
#define TCON (*(volatile unsigned long *)0x51000008)
#define TCNTB0 (*(volatile unsigned long *)0x5100000c)
#define TCMPB0 (*(volatile unsigned long *)0x51000010)
#define TCNTO0 (*(volatile unsigned long *)0x51000014)
#define GSTATUS1 (*(volatile unsigned long *)0x560000B0)
（6）serial.h程序如下：
void uart0_init(void);
void putc(unsigned char c);
unsigned char getc(void);
int isDigit(unsigned char c);
int isLetter(unsigned char c);
（7）Makefile程序如下：
objs := head.o init.o serial.o main.o
uart.bin: $(objs)
arm-linux-ld -Tuart.lds -o uart_elf $^
arm-linux-objcopy -O binary -S uart_elf $@
arm-linux-objdump -D -m arm uart_elf > uart.dis
%.o:%.c
arm-linux-gcc -nostdlib -Wall -O2 -c -o $@ $<
%.o:%.S
arm-linux-gcc -nostdlib -Wall -O2 -c -o $@ $<
clean:
rm -f uart.bin uart_elf uart.dis *.o
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