中断法实现按键点灯

Myth丶恋晨 2022-07-13 04:10 162阅读 0赞

汇编代码

.global _start					/* 声明一个全局的标号 */
    .global key_isr
    _start:
    	/* 设置栈，以调用c函数 */
    	ldr	sp, =0x40000000		
    
    	/* 开总中断	*/
    	mrs r0, cpsr
    	bic r0, r0, #0x00000080		/* 清楚第7位，IRQ中断禁止位，写0使能IRQ */
    	msr cpsr, r0
    
    	bl main						/* 跳转到C函数去执行 */
    
    halt:
    	b halt
    
    key_isr:
    	/* 计算返回地址:PC的值等于当前执行的地址+8，当CPU正要执行某条指令时（还未执行），被中断，
    	** 这是这条刚要执行的指令的地址刚好=PC-4 */
    	sub lr, lr, #4
    	stmfd sp!, {r0-r12, lr}  	/* 保护现场 */
    	bl key_handle
    	/* 恢复现场 */
    	ldmfd sp!, {r0-r12, pc}^  	/* ^表示把spsr恢复到cpsr */

C语言部分的代码

#define GPC0CON				*((volatile unsigned int *)0xE0200060)
    #define GPC0DAT				*((volatile unsigned int *)0xE0200064)
    
    #define GPH0CON				*((volatile unsigned int *)0xE0200C00)
    #define GPH0DAT				*((volatile unsigned int *)0xE0200C04)
    
    #define EXT_INT_0_CON 		*((volatile unsigned int *)0xE0200E00)
    #define EXT_INT_0_MASK		*((volatile unsigned int *)0xE0200F00)
    
    #define VIC0INTSELECT		*((volatile unsigned int *)0xF200000C)
    #define VIC0INTENABLE 		*((volatile unsigned int *)0xF2000010)
    
    #define VIC0VECTADDR0		*((volatile unsigned int *)0xF2000100)
    #define VIC0VECTADDR1		*((volatile unsigned int *)0xF2000104)
    
    #define VIC0ADDRESS  		*((volatile unsigned int *)0xF2000F00)
    
    #define EXT_INT_0_PEND		*((volatile unsigned int *)0xE0200F40)
    
    extern void key_isr(void);
    
    void key_handle()
    {	
    	volatile unsigned char key_code = EXT_INT_0_PEND & 0x3;
    	
    	VIC0ADDRESS = 0;		/* 清中断向量寄存器 */
    	EXT_INT_0_PEND |= 3;	/* 清中断挂起寄存器 */
    	
    	if (key_code == 1)		/* key1 */
    		GPC0DAT ^= 1 << 3;	/* toggle LED1 */
    	else if (key_code == 2)	/* key2 */
    		GPC0DAT ^= 1 << 4;	/* toggle LED2 */
    }
    
    int main()
    {
    	GPC0CON &= ~(0xFF << 12);
    	GPC0CON |= 0x11 << 12;					/* 配置GPC0_3和GPC0_4为输出：LED1和LED2 */
    	GPH0CON |= 0xFF << 0;					/* 配置GPH0_0和GPH0_1为外部中断：key1和key2 */
    	
    	EXT_INT_0_CON &= ~(0xFF << 0);
    	EXT_INT_0_CON |= 2 | (2 << 4);			/* 配置EXT_INT[0]和EXT_INT[1]为下降沿触发 */
    	EXT_INT_0_MASK &= ~3;					/* 取消屏蔽外部中断EXT_INT[0]和EXT_INT[1] */
    	
    	VIC0INTSELECT &= ~3;					/* 选择外部中断EXT_INT[0]和外部中断EXT_INT[1]为IRQ类型的中断 */
    	
    	VIC0INTENABLE |= 3;						/* 使能外部中断EXT_INT[0]和EXT_INT[1] */
    	
    	VIC0VECTADDR0 = (int)key_isr;			/* 当EXT_INT[0]触发中断，即用户按下key1时，
    											 CPU就会自动的将VIC0VECTADDR0的值赋给VIC0ADDRESS并跳转到这个地址去执 */
    	VIC0VECTADDR1 = (int)key_isr;
    	
    	while (1);
    	
    	return 0;
    }