4. ARM中断处理实现

1. 中断概念

为什么要有中断？cpu和外设之间要进行通信，那么cpu怎么知道外设有数据来，有两种方式：

2. 中断工作流程图

cpu处理步骤：
1.保存现场
2.向中断控制器查询是哪个中断
3.执行中断处理程序
4.恢复现场
GPIO控制器：
1.CON：功能配置寄存器
2.INTC：触发方式
3.PEND：中断记录标志位
4.MASK：开关

3. 中断控制器工作流程图

以其中的一组中断控制为例：

每32个中断源为一组，fiq为快速中断，irq为普通中断，vic中有32个寄存器与中断源一一对应，存储的是中断函数的地址，address寄存器保存当前中断的中断函数地址，当enable打开时才会通知cpu有中断来临

4. 外部中断驱动实现

4.1 汇编程序

start.s:

.global _start
_start:
		b reset
		b undef
		b swi
		b abt_pre
		b abt_dat
		b reserved
		b irq
		b fiq
reset:
		@重新映射异常向量表到0x40008000 
		ldr r0, =0x40008000 
		mcr p15, 0, r0, c12, c0, 0
		@打开中断的总开关
		mrs r0, cpsr
		bic r0, r0, #(0x1 << 7)
		msr cpsr, r0 
		bl main
		
undef:
swi:
abt_pre:
abt_dat:
reserved:
irq:
		ldr sp, =0x420000000   @初始化栈指针
		stmfd sp!, {r0-r12,lr}
		bl irq_handler         @调到中断函数
		ldmfd sp!, {r0-r12,lr}
		subs pc, lr, #4
fiq:

4.2 C语言程序

main.c:

#define VICOINTSELECT (*(volatile unsigned int *)0xF200000C)
#define VIC0VECTADDR (*(volatile unsigned int *)0xF2000100)
#define VIC0INTENABLE (*(volatile unsigned int *)0xF2000010)
#define VIC0ADDRESS (*(volatile unsigned int *)0xF2000F00)
#define GPH0CON  (*(volatile unsigned int *)0xE0200C00))
#define EXT_INT_0_CON (*(volatile unsigned int *)0xE0200E00)
#define EXT_INT_0_MASK (*(volatile unsigned int *)0xE0200F00)
#define EXT_INT_0_PEND (*(volatile unsigned int *)0xE0200F40)

void key1_handler(void)
{
	int (*printf)(char *format,...)=(void *)0x3ff13e54;
	printf("hello key1..\n");
	//清理GPIO里面的中断记录
	EXT_INT_0_PEND  = 0x1;

}
int main()
{
	//初始化中断控制器
	VICOINTSELECT = 0;
	VIC0VECTADDR = (unsigned int)key1_handler;
	VIC0INTENABLE |= 0x1; //开启0号中断
	//初始化按键，GPIO
	GPH0CON |=0xf;//设置成中断功能
	EXT_INT_0_CON &=~0xf;
	EXT_INT_0_CON |=0x3;
	EXT_INT_0_MASK &=~0x1;
	while(1)
	{
		;
	}
	return 0;
}
//中断处理函数
void irq_handler()
{
	void(*handler)();
	handler=(void *)VIC0ADDRESS ;
	handler();
	//清理中断控制器
	VIC0ADDRESS=0;
}

4.3 编译和运行

PS:注意链接部分语句

上机结果如下：

5. 优化中断程序

5.1 将所有中断的操作封装

irq.c：

#define VICOINTSELECT (*(volatile unsigned int *)0xF200000C)
#define VIC1INTSELECT (*(volatile unsigned int *)0xF210000C)
#define VIC2INTSELECT (*(volatile unsigned int *)0xF220000C)
#define VIC3INTSELECT (*(volatile unsigned int *)0xF230000C)

#define VIC0VECTADDR (volatile unsigned int *)0xF2000100
#define VIC1VECTADDR (volatile unsigned int *)0xF2100100
#define VIC2VECTADDR (volatile unsigned int *)0xF2200100
#define VIC3VECTADDR (volatile unsigned int *)0xF2300100

#define VIC0INTENABLE (*(volatile unsigned int *)0xF2000010)
#define VIC1INTENABLE (*(volatile unsigned int *)0xF2100010)
#define VIC2INTENABLE (*(volatile unsigned int *)0xF2200010)
#define VIC3INTENABLE (*(volatile unsigned int *)0xF2300010)

#define VIC0ADDRESS (*(volatile unsigned int *)0xF2000F00)
#define VIC1ADDRESS (*(volatile unsigned int *)0xF2100F00)
#define VIC2ADDRESS (*(volatile unsigned int *)0xF2200F00)
#define VIC3ADDRESS (*(volatile unsigned int *)0xF2300F00)

//中断控制器初始化函数
int request_irq(int irq, void(*handler)())
{
	if(irq>=0 && irq <= 31)
	{
		VICOINTSELECT = 0;//初始化中断控制器
		VIC0VECTADDR[irq] = (unsigned int)handler; //注册中断函数
		VIC0INTENABLE |= 0x1<<irq; //开启中断
	}
	else if(irq>=32 && irq<=63)
	{
		irq-=32;
		VIC1INTSELECT = 0;
		VIC1VECTADDR[irq] = (unsigned int)handler;
		VIC1INTENABLE |= 0x1<<irq; //开启中断
	}
	else if(irq>=64 && irq <=95)
	{
		irq-=64;
		VIC2INTSELECT = 0;
		VIC2VECTADDR[irq] = (unsigned int)handler;
		VIC2INTENABLE |= 0x1<<irq; //开启中断
	}
	else if(irq>=96 && irq <=128)
	{
		irq-=96;
		VIC3INTSELECT = 0;
		VIC3VECTADDR[irq] = (unsigned int)handler;
		VIC3INTENABLE |= 0x1<<irq; //开启中断
	}

}

//中断处理函数
void irq_handler()
{
	void(*handler)();
	
	//判断是那个中断发生
	if(VIC0ADDRESS !=0 )
		handler=(void *)VIC0ADDRESS;
	else if(VIC1ADDRESS !=0)
		handler=(void *)VIC1ADDRESS;
	else if(VIC2ADDRESS !=0)
		handler=(void *)VIC2ADDRESS;
	else if(VIC3ADDRESS !=0)
		handler=(void *)VIC3ADDRESS;
		
	//执行绑定的中断处理函数
	handler();
	
	//清理中断控制器
	VIC0ADDRESS=0;
	VIC1ADDRESS=0;
	VIC2ADDRESS=0;
	VIC3ADDRESS=0;
}

5.2 修改main

修改main.c：

#define GPH0CON  (*(volatile unsigned int *)0xE0200C00))
#define EXT_INT_0_CON (*(volatile unsigned int *)0xE0200E00)
#define EXT_INT_0_MASK (*(volatile unsigned int *)0xE0200F00)
#define EXT_INT_0_PEND (*(volatile unsigned int *)0xE0200F40)

void key1_handler(void)
{
	int (*printf)(char *format,...)=(void *)0x3ff13e54;
	printf("hello key1..\n");
	//清理GPIO里面的中断记录
	EXT_INT_0_PEND  = 0x1;

}
int main()
{
	//初始化中断控制器
	request_irq(0,key1_handler);
	//初始化按键，GPIO
	GPH0CON |=0xf;//设置成中断功能
	
	EXT_INT_0_CON &=~0xf;
	EXT_INT_0_CON |=0x3;
	
	EXT_INT_0_MASK &=~0x1;//使能
	while(1)
	{
		;
	}
	return 0;
}

5.3 编译和运行

6. WDT中断实现

看门狗定时器（WDT，Watch Dog Timer）是单片机的一个组成部分，它实际上是一个计数器，一般给看门狗一个数字，程序开始运行后看门狗开始计数。如果程序运行正常，过一段时间CPU应发出指令让看门狗置零，重新开始计数。如果看门狗增加到设定值就认为程序没有正常工作，强制整个系统复位。

6.1 WDT驱动实现

wdt.c

#define WTCON   (*(volatile unsigned int *)0xE2700000))
#define WTDAT   (*(volatile unsigned int *)0xE2700004))
#define WTCNT 	(*(volatile unsigned int *)0xE2700008))
#define WTCLRINT (*(volatile unsigned int *)0xE270000C))
void key1_handler(void)
{
	int (*printf)(char *format,...)=(void *)0x3ff13e54;
	printf("hello wdt..\n");
	//清理GPIO里面的中断记录
	WTCLRINT  = 1;//清理中断

}

void wdt_init()
{
	WTCON = (65<<8)|(0x1<<5)|(0x1<<3)|(0x1<<2)|0;
	//t=（32*（65+1））/ 66M = 32us
	WTCNT = 1000*1000/32;//1s
	WTDAT = 1000*1000/32; //首次喂狗
}
int main()
{
	//初始化看门狗
	wdt_init();
	//初始化中断控制器
	request_irq(27,wdt_handler);//看门狗是27号中断
	while(1)
	{
		;
	}
	return 0;
}

6.2 编译和运行