裸板调试方法---点灯法

bl led_flicker

led_flicker:
// 配置寄存器
ldr r0, =0x56000050
ldr r1, (1<<4*2)
str r1, [r0]

ldr r0, =0x56000054
ldr r1, =0
ldr r2, =(1<<4)

loop:
// 循环点亮，熄灭
str r1, [r0]
bl delay
str r2, [r0]
bl delay

delay:
ldr r3, =30000

1:
sub r3, r3, #1
cmp r3, #0
bne 1b
mov pc, =lr