调试了好久总算成功发动了板子，这个程序分两个部分，一个是发动代码boot.s担任初始化硬件并复制前4k的程序到内存中履行。别的一个是主程序文件main.c，main设置UART并运用串口循环输出打印一个类似于shell的界面，能够接纳指令，但暂时没做指令解说,功用还不全，首要是为了看看能不能完结根本的BOOTLOADER功用。
mian.c
#define BUF_SIZE 100
#define GPHCON (*(volatile unsigned long *)0x56000070)
#define GPHUP (*(volatile unsigned long *)0x56000078)
#define ULCON0 (*(volatile unsigned long *)0x50000000)
#define UCON0 (*(volatile unsigned long *)0x50000004)
#define UFCON0 (*(volatile unsigned long *)0x50000008)
#define UTRSTAT0 (*(volatile unsigned long *)0x50000010)
#define UTXH0 (*(volatile unsigned long *)0x50000020)
#define URXH0 (*(volatile unsigned long *)0x50000024)
#define UBRDIV0 (*(volatile unsigned long *)0x50000028)
void init_uart();
void newline();
void bzero(char *buf,int size);
void do_cmd(char *s);
void send_char(char ch);
void send_msg(char *s);
void get_msg(char *buf,int size);
void print_shell();
void delay(int i);
void main(void)
{
init_uart();
char msg[BUF_SIZE];
while(1)
{
bzero(msg,BUF_SIZE);
newline();
print_shell();
get_msg(msg,BUF_SIZE – 2);
do_cmd(msg);
// delay(4);
}
}
void init_uart()
{
GPHCON &= ~(0xf0);
GPHCON |= 0xa0;
GPHUP = 0xc;
ULCON0 = 0x03;
UCON0 = 0x05;
UFCON0 = 0;
UBRDIV0 = 27;
}
void newline()
{
send_char(\r);
send_char(\n);
}
void bzero(char *buf,int size)
{
int i;
for(i = 0;i < size;i++)
buf[i] = 0;
}
void send_char(char ch)
{
while(!((UTRSTAT0 >> 1) & 1));
UTXH0 = ch;
}
void send_msg(char *s)
{
while(*s != \0)
{
while(!((UTRSTAT0 >> 1) & 1));
UTXH0 = *s;
s++;
}
}
void get_msg(char *buf,int size)
{
int i;
char ch;
for(i = 0;i < size;i++)
{
while(!(UTRSTAT0 & 1))
;
ch = URXH0;
if(ch == \n || ch == \0 || ch == 😉
{
buf[i] = \r;
buf[i] = \n;
break;
}
buf[i] = ch;
send_char(ch);
}
}
void print_shell()
{
send_msg(“[sillyboot@leonlew]”);
}
void do_cmd(char *s)
{
newline();
send_msg(“Unknown command:”);
send_msg(s);
}
void delay(int i)
{
int j;
for(j = 0;j < 0x40000 * i;j++)
;
}
boot.s
b RESET
@b UDF
@b SWI
@b PABT
@b DABT
@b RESERVE
@b IRQ
@b FIQ
RESET:
@svc形式，IRQ，FIQ封闭
mrs r0,cpsr
bic r0,r0,#0x1f
orr r0,r0,#0xd3
msr cpsr,r0;
@初始化时钟
ldr r0,=0x4c000004
ldr r1,=0x7f021
str r1,[r0]
ldr r0,=0x4c000014
mov r1,#5
str r1,[r0]
@作业在异步形式
mrc p15,0,r0,c1,c0,0
orr r0,r0,#0xc0000000
mcr p15,0,r0,c1,c0,0
@封闭watch dog
ldr r0,=0x53000000
mov r1,#0x0
str r1,[r0]
@初始化SDRAM
@BWSCON寄存器
ldr r0,=0x48000000
ldr r1,=0x02000000
str r1,[r0]
@BANKCON6寄存器
ldr r0,=0x4800001c
ldr r1,=0x00018005
str r1,[r0]
@refresh寄存器设置
ldr r0,=0x48000024
ldr r1,=0x8c04f5
str r1,[r0]
@banksize寄存器设置
ldr r0,=0x48000028
mov r1,#1
str r1,[r0]
@MRSRB6寄存器设置
ldr r0,=0x4800002c
mov r1,#0x30
str r1,[r0]
@翻开一切LED灯
ldr r0,=0x56000058
ldr r1,[r0]
bic r1,r1,#0xf0
orr r1,r1,#0xf0
str r1,[r0]
ldr r0, =0x56000050
ldr r1, [r0]
bic r1, r1, #0xff00
orr r1, r1, #0x5500
str r1, [r0]
ldr r0, =0x56000054
ldr r1, [r0]
and r1,r1,#0x0f
ldr r0, =0x56000050
ldr r1, [r0]
bic r1, r1, #0xff00
orr r1, r1, #0x5500
str r1, [r0]
@测验SDRAM
ldr r0,=0x32000000
ldr r1,=0x22334455
str r1,[r0]
@复制程序到0x33000000
@从地址0开端复制4K的内容到0x33000000
mov r1,#0
ldr r2,=0x33000000
mov r3,#0x1000
loop_cp:
ldr r4,[r1],#4
str r4,[r2],#4
cmp r1,r3
bne loop_cp
@复制完结测验，封闭第一和第三个LED
ldr r2,[r0]
cmp r2,r1
bne end
ldr r0, =0x56000054
ldr r1, [r0]
orr r1,r1,#0xa0
str r1, [r0]
end:
@设置栈
ldr sp,=0x33400000
ldr pc,=main
链接脚本
lscript.lds
SECTIONS
{
. = 0x33000000;
.text :
{
*.o(.text);
}
. = ALIGN(4);
.data :
{
*.data(.data);
}
}
Makefile
boot:
@arm-linux-gcc -c -o main.o main.c
@arm-linux-as -o boot.o boot.s
@arm-linux-ld -T lscript.lds boot.o main.o -o boot
@arm-linux-objcopy -I elf32-littlearm -O binary boot /myboot.bin
@arm-linux-nm -s boot main.o > System.map
main:
@arm-linux-gcc -c -o main.o main.c
clean:
@rm -f boot *.o
