正文
Tiny4412中断之看门狗
小程序：扫一扫查出行【扫一扫了解最新限行尾号】
复制小程序
一：看门狗（WDT watch dog timer）
看门狗其实是一个计数器，它的作用就是防止程序陷入死循环或者程序运行跑飞；看门狗是一个硬件，它的工作原理是，初始化给他一个值，它会过一段时间减一，直到这个数减为0，它将会产生一个中断信号或者reset信号，致使我们系统复位，而又时候我们不想让它过一会儿就重启又想预防死机，那么我们就可以在这个数减到快要接进0的时候，给它重新赋值；这样就不会触发reset信号，但当程序跑飞时机器死机时，它就会减到零，进行操作系统复位；
具体看下图所示：输入时钟为PCLK（该时钟频率等于系统的主频），它经过两级分频(Prescaler和frequency division factor)，最后将分频后的时钟作为该定时器的输入时钟，当计数器期满后可以产生中断或者复位信号。
看门狗计数器公式如下：
t_watchdog = 1/( PCLK / (Prescaler value + 1) / Division_factor )
通过tiny4412用户手册我们可以找到看门狗的中断号为 75 （如下图）：
预分频器Prescaler及分频因子Division factor的值在WTCON（看门狗时钟控制寄存器)中设置，如下图：
今天的程序是使用watchdog来实现led灯的闪烁，下面贴出代码：
#ifndef __BUNFLY_H
#define __BUNFLY_H #define ICCICR_CPU0 (*(volatile unsigned long *)0x10480000)
#define ICCPMR_CPU0 (*(volatile unsigned long *)0x10480004)
#define ICDDCR (*(volatile unsigned long *)0x10490000)
#define ICDIPR0_CPU0 (*(volatile unsigned long *)0x10490400)
#define ICDIPTR0_CPU0 (*(volatile unsigned long *)0x10490800)
#define ICDISER0_CPU0 (*(volatile unsigned long *)0x10490100)
#define ICDSGIR (*(volatile unsigned long *)0x10490f00)
#define ICCEOIR_CPU0 (*(volatile unsigned long *)0x10480010)
#define ICCIAR_CPU0 (*(volatile unsigned long *)0x1048000c)
#define ICDIPR2_CPU0 (*(volatile unsigned long *)0x10490408)
#define ICDIPTR2_CPU0 (*(volatile unsigned long *)0x10490808)
#define ICDIPR3_CPU0 (*(volatile unsigned long *)0x1049040c)
#define ICDIPTR3_CPU0 (*(volatile unsigned long *)0x1049080c)
#define ICDIPR16_CPU0 (*(volatile unsigned long *)0x10490440)
#define ICDIPTR16_CPU0 (*(volatile unsigned long *)0x10490840)
#define ICDIPR18_CPU0 (*(volatile unsigned long *)0x10490448)
#define ICDIPTR18_CPU0 (*(volatile unsigned long *)0x10490848)
#define ICDISER2_CPU0 (*(volatile unsigned long *)0x10490108) #define WTCON (*(volatile unsigned long *)0x10060000)
#define WTDAT (*(volatile unsigned long *)0x10060004)
#define WTCNT (*(volatile unsigned long *)0x10060008)
#define WTCLRINT (*(volatile unsigned long *)0x1006000C) #define EXT_INT43CON (*(volatile unsigned long *)0x11000e0c)
#define EXT_INT43_MASK (*(volatile unsigned long *)0x11000f0c)
#define EXT_INT43_PEND (*(volatile unsigned long *)0x11000f4c)
#define GPX3CON (*(volatile unsigned long *)0x11000c60) #define GPM4CON (*(volatile unsigned long *)0x110002e0)
#define GPM4DAT (*(volatile unsigned long *)0x110002e4) #endif //__BUNFLY_H
#include "bunfly.h" void (*udelay)(int) = 0xc3e25f90;
int (*printf)(char *, ...) = 0xc3e114d8;
void enable_mmu();
void init_table(unsigned long *addr);
void memcpy(unsigned char *dest, unsigned char *src, int len);
extern unsigned long vector_start;
void do_irq();
void led_on();
void led_off(); int main()
{
memcpy(0x70000000, vector_start, 0x1000);
enable_mmu(); *(unsigned long *)0x47000000 = do_irq; //step 1: set cpu permit interrupt
__asm__ __volatile__(
"mrs r0, cpsr\n"
"bic r0,r0, #0x80\n"
"msr cpsr, r0\n"
:::"r0"
); //step 2: set GIC (cgi) enable
ICCICR_CPU0 = ; //中断总开关
ICCPMR_CPU0 =0xff;//设置最低优先级（门槛）
ICDDCR = ; //本中断开关
ICDIPR18_CPU0 = ( << );//设置本中断优先级
ICDIPTR18_CPU0 = ( << );//选择指定的cpu进行中断处理
ICDISER2_CPU0 = ( << );//启用本中断 //step 3: set watch dog timer
WTCNT = ;
WTDAT = ;
WTCON = ( << ) | ( << ) | ( << ) | ( << ); printf("welcom back\n");
} void do_irq()
{
WTCLRINT = ;//清中断
printf("wang wang wang\n");
static int flags = ;
if(flags) {
led_on();
flags = ;
}
else {
led_off();
flags = ;
}
} void led_on()
{
GPM4CON &= ~0xffff;
GPM4CON |= 0x1111;
GPM4DAT &= ~0xf;
} void led_off()
{ GPM4CON &= ~0xffff;
GPM4CON |= 0x1111;
GPM4DAT |= 0xf;
} void memcpy(unsigned char *dest, unsigned char *src, int len)
{
int i = ;
for(i = ; i < len; i++) {
dest[i] = src[i];
}
} void enable_mmu()
{
/*构建表*/
unsigned long addr = 0x50000000;
init_table(addr);
/*打开mmu*/
unsigned long mmu = ;
mmu = | ( << ) | ( << ) | ( << );
__asm__ __volatile__ (
"mov r0, #3\n"
"MCR p15, 0, r0, c3, c0, 0\n"//设置为管理员
"MCR p15, 0, %0, c2, c0, 0\n"//设置表的地址
"MCR p15, 0, %1, c1, c0, 0\n"//开启mmu
:
: "r" (addr), "r" (mmu)
:
); } __asm__( "vector: \n"
" b reset\n"
" b und\n"
" b swi\n"
" b pre_abt\n"
" b data_abt\n"
" .word 0x0\n"
" b irq\n"
" b fiq\n"
"reset:\n"
"und:\n"
" mov sp, #0x47000000\n"
" stmdb sp!, {r0-r12, lr}\n" " ldr r3, =0x47000004\n"
" ldr r2, [r3]\n"
" blx r2\n" " mov sp, #0x47000000\n"
" ldmdb sp, {r0-r12, pc}^ \n" "swi:\n"
" mov sp, #0x47000000\n"
" stmdb sp!, {r0-r12, lr}^\n" " mov sp, #0x47000000\n"
" ldmdb sp, {r0-r12, pc}^ \n" "pre_abt:\n" "data_abt:\n"
" mov sp, #0x47000000\n"
" sub lr, lr, #4\n"
" stmdb sp!, {r0-r12, lr}\n" " ldr r3, =0x47000008\n"
" ldr r2, [r3]\n"
" blx r2\n" " mov sp, #0x47000000\n"
" ldmdb sp, {r0-r12, pc}^ \n"
"irq:\n" " mov sp, #0x47000000\n"
" sub lr, lr, #4\n"
" stmdb sp!, {r0-r12, lr}\n" " ldr r3, =0x47000000\n"
" ldr r2, [r3]\n"
" blx r2\n" " mov sp, #0x47000000\n"
" ldmdb sp, {r0-r12, pc}^ \n" "fiq:\n" ".global vector_start\n"
"vector_start: \n"
".word vector \n " ); void init_table(unsigned long *addr)
{
unsigned long va = ;
unsigned long phys = ; //0x40000000-0x80000000 -> 0x40000000-0x80000000
for(va = 0x40000000; va < 0x80000000; va += 0x100000) {
phys = va;
addr[va >> ] = phys | ;
} //0x10000000-0x14000000 -> 0x10000000-0x140000000
for(va = 0x10000000; va < 0x14000000; va += 0x100000) {
phys = va;
addr[va >> ] = phys | ;
}
//0x10000000-0x14000000 -> 0x10000000-0x140000000
for(va = 0x0; va < 0x10000000; va += 0x100000) {
phys = va + 0x70000000;
addr[va >> ] = phys | ;
} }
