A20 裸机点亮LED灯
写了个简单的裸机点灯程序,放到SD或者NAND上,都不能点亮,现在点灯只有在U-BOOT起来后才可以操作。代码如下,simon_li@ubuntu_precise:~/NAND/led$ cat led.S
.text
.global _start
_start:
ldr r0,=0x01c20c94
mov r1,#0x0
str r1,
ldr sp,=4096
bl main
main_loop:
b main_loop
simon_li@ubuntu_precise:~/NAND/led$ cat main.c
#define GPBCON (*(volatile unsigned long *)0x01c20824)
#define GPBDAT (*(volatile unsigned long *)0x01c20834)
int main(void)
{
GPBCON = 0x00100000;
GPBDAT = 0x00000000;
return 0;
}
汇编写的,不是很懂,可以用c语言写:)
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