S3C2440 用按键控制LED

转自《嵌入式Linux应用开发完全手册》

1. 先看电路图

2. 配置按键为输入，LED为输入

（1）通过crt0.S转入C程序

.text
.global _start
_start:

	ldr  r0, =0x53000000    @ WATCHDOG寄存器地址

	mov  r1, #0x0

	str  r1, [r0]           @ 写入0，禁止WATCHDOG，否则CPU会不断重启

	ldr sp, =1024*4         @ 设置堆栈，注意：不能大于4K，因为可用的内存只有4K

	                        @ nand flash中的代码在复位后会移到内部ram中，此ram只有4K

	bl  main                @ 调用C程序中的main函数

halt_loop:

	b   halt_loop

（2）key_led.c

#define GPFCON  (*(volatile unsigned long *) 0x56000050)

#define GPFDAT   (*(volatile unsigned long *) 0x56000054)

#define GPGCON (*(volatile unsigned long *) 0x56000060)

#define GPGDAT   (*(volatile unsigned long *) 0x56000064)

#define GPF4_out (1<<(4*2))

#define GPF5_out (1<<(5*2))

#define GPF6_out (1<<(6*2))

#define GPF4_msk (3<<(4*2))

#define GPF5_msk (3<<(5*2))

#define GPF6_msk (3<<(6*2))

#define GPF0_in (0<<(0*2))

#define GPF2_in (0<<(2*2))

#define GPG3_in (0<<(3*2))

#define GPF0_msk (3<<(0*2))

#define GPF2_msk (3<<(2*2))

#define GPG3_msk (3<<(3*2))

int main()

{

unsigned long dwDat;

GPFCON &= ~(GPF4_msk | GPF5_msk | GPF6_msk);

GPFCON |= GPF4_out | GPF5_out | GPF_out;

GPFCON &= ~(GPF0_msk | GPF2_msk);

GPFCPN |= GPF0_in | GPF2_in;

GPGCON &= ~GPG3_msk;

GPGCON != GPG3_in;

while (1) {

dwDat = GPFDAT;

if (dwDat & (1<<0))

GPFDAT |= (1<<4);

else

GPFDAT &= ~(1<<4);

if (dwDat & (1<<2))

GPFDAT |= (1<<5);

else

GPFDAT &= ~(1<<5);

dwDat = GPGDAT;

if (dwDat & (1<<3))

GPFDAT |= (1<<6);

else

GPFDAT &= ~(1<<6);

}

return 0;

}

3. 总结

清0使用 &= ~

置1使用 |=