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,=4096
      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=0;
}


void clock_init(void)
{
    CLKDIVN=0x03;    
    __asm__
    (
    "mrc p15,0,r1,c1,c0,0
"
    "orr r1,r1,#0xc0000000
"
    "mcr p15,0,r1,c1,c0,0
"
    );
       MPLLCON=((0x5c<<12)|(0x01<<4)|(0x02));
}

void sdram_init(void)
{
    volatile unsigned long *sdram_base=(volatile unsigned long *)0x48000000;
    sdram_base[0]  = 0x22011110;     
    sdram_base[1]  = 0x00000700;    
    sdram_base[2]  = 0x00000700;    
    sdram_base[3]  = 0x00000700;   
    sdram_base[4]  = 0x00000700;    
    sdram_base[5]  = 0x00000700;    
    sdram_base[6]  = 0x00000700;    
    sdram_base[7]  = 0x00018005;    
    sdram_base[8]  = 0x00018005;    
    sdram_base[9]  = 0x008C04F4;
    sdram_base[10] = 0x000000B1;    
    sdram_base[11] = 0x00000030;    
    sdram_base[12] = 0x00000030;     
    
}

void copy_steppingstone_to_sdram(void)
{
    unsigned int *sour=(unsigned int *)0x00000000;
    unsigned int *dest=(unsigned int *)0x30000000;
    
    while(sour<=(unsigned int *)4096)
    {
        *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=((50000000/(115200*16))-1);    
}

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(1)
    putc(getc()+1);    
    return 0;
}

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