uarts裸机程序

硬件平台：JZ2440

实现功能：向串口软件实现输出putchar函数

start.s   --> 设置堆栈，关闭看门狗，初始化时钟，初始化sdram

init.c      -->初始化函数

uart.c    -->初始化串口寄存器

uart.h    -->

main.c  -->

start.s源码：

.extern main
.text
.global _start
_start:
      ldr sp,=
      bl  watchdog_init
      bl  clock_init
      bl  sdram_init
      bl  copy_steppingstone_to_sdram
      ldr pc,=sdram
sdram:
      ldr sp,=0x34000000
      ldr lr,=main_return
      ldr pc,=main
main_return:
      b main_return

init.c 源码：

//watchdog
#define WTCON      (*(volatile unsigned long *)0x53000000)

//clock
#define LOCKTIME   (*(volatile unsigned long *)0x4c000000)
#define MPLLCON    (*(volatile unsigned long *)0x4c000004)
#define CLKDIVN    (*(volatile unsigned long *)0x4c000014)

//sdram
#define BWSCON     (*(volatile unsigned long *)0x48000000)
#define BANKCON0   (*(volatile unsigned long *)0x48000004)
#define BANKCON1   (*(volatile unsigned long *)0x48000008)
#define BANKCON2   (*(volatile unsigned long *)0x4800000c)
#define BANKCON3   (*(volatile unsigned long *)0x48000010)
#define BANKCON4   (*(volatile unsigned long *)0x48000014)
#define BANKCON5   (*(volatile unsigned long *)0x48000018)
#define BANKCON6   (*(volatile unsigned long *)0x4800001c)
#define BANKCON7   (*(volatile unsigned long *)0x48000020)
#define REFRESH    (*(volatile unsigned long *)0x48000024)
#define BANKSIZE   (*(volatile unsigned long *)0x48000028)
#define MRSRB6     (*(volatile unsigned long *)0x4800002c)
#define MRSRB7     (*(volatile unsigned long *)0x48000030)

void watchdog_init(void)
{
    WTCON=;
}

void clock_init(void)
{
    CLKDIVN=0x03;
    __asm__
    (
    "mrc p15,0,r1,c1,c0,0\n"
    "orr r1,r1,#0xc0000000\n"
    "mcr p15,0,r1,c1,c0,0\n"
    );
       MPLLCON=((0x5c<<)|(0x01<<)|(0x02));
}

void sdram_init(void)
{
    volatile unsigned long *sdram_base=(volatile unsigned long *)0x48000000;
    sdram_base[]  = 0x22011110;
    sdram_base[]  = 0x00000700;
    sdram_base[]  = 0x00000700;
    sdram_base[]  = 0x00000700;
    sdram_base[]  = 0x00000700;
    sdram_base[]  = 0x00000700;
    sdram_base[]  = 0x00000700;
    sdram_base[]  = 0x00018005;
    sdram_base[]  = 0x00018005;
    sdram_base[]  = 0x008C04F4;
    sdram_base[] = 0x000000B1;
    sdram_base[] = 0x00000030;
    sdram_base[] = 0x00000030;     

}

void copy_steppingstone_to_sdram(void)
{
    unsigned int *sour=(unsigned int *)0x00000000;
    unsigned int *dest=(unsigned int *)0x30000000;

    while(sour<=(unsigned int *))
    {
        *dest++=*sour++;
    }
}

uart.c 源码：

//uart
#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  UERSTAT0    (*(volatile unsigned long *)0x50000014)
#define  UTXH0       (*(volatile unsigned char *)0x50000020)
#define  URXH0       (*(volatile unsigned char *)0x50000024)
#define  UBRDIV0     (*(volatile unsigned long *)0x50000028)

//GPH
#define  GPHCON      (*(volatile unsigned long *)0x56000070)
#define  GPHDAT      (*(volatile unsigned long *)0x56000074)
#define  GPHUP       (*(volatile unsigned long *)0x56000078)

void uart0_init(void)
{
    GPHCON|=0xa0;
    GPHUP=0x0c;

    ULCON0=0x03;
    UCON0=0x05;
    UFCON0=0x00;
    UMCON0=0x00;
    UBRDIV0=((/(*))-);
}

unsigned char getc(void)
{
    while(!(UTRSTAT0 & 0x01));
    return URXH0;
}

void putc(unsigned char date)
{
    while(!(UTRSTAT0 & 0x02));
    UTXH0=date;
}

uart.h 源码：

#ifndef _UART_H_
#define _UART_H_ 

void uart0_init(void);
unsigned char getc(void);
void putc(unsigned char date);

#endif

main.c 源码：

#include"uart.h"

int main(void)
{
    uart0_init();
    while()
    putc(getc()+);
    return ;
}

连接脚本uart.lds ：

SECTIONS
{
  . = 0x30000000;
  .text  : {*(.test)}
  .rodata : {*(.rodata)}
  .dtat  : {*(.data)}
  .bss   : {*(.bss) *(COMMON)}

}

Makefile:

objs:= start.o init.o uart.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:%.s
    arm-linux-gcc  -o $@ -c $<

%.o:%.c
    arm-linux-gcc  -o $@ -c $<

clean:
    rm -f *.o *.bin *.dis uart_elf