原创 STM8的C语言编程（6）－－8位定时器应用之二

                 STM8的C语言编程（6）－－8位定时器应用之二

今天进行的实验依然是用定时器4，只不过改成了用中断方式来实现，由定时器4的中断服务程序来驱动LED的闪烁。

实现中断方式的关键点有几个，第一个关键点就是要打开定时器4的中断允许位，在定时器4的IER寄存器中有定义。第二个关键点，就是打开CPU的全局中断允许位，在汇编语言中，就是执行RIM指令，在C语言中，用下列语句实现：

_asm("rim");

第3个关键点就是中断服务程序的框架或写法，中断服务程序的写法如下：

@far @interrupt void TIM4_UPD_OVF_IRQHandler (void)

{

    // 下面是中断服务程序的实体

}                            

第4个关键点就是要设置中断向量，即将中断服务程序的入口填写到中断向量表中，如下所示，将IRQ23对应的中断服务程序的入口填写成TIM4_UPD_OVF_IRQHandler

struct interrupt_vector const _vectab[] = {

      {0x82, (interrupt_handler_t)_stext}, /* reset */

      {0x82, NonHandledInterrupt}, /* trap  */

      {0x82, NonHandledInterrupt}, /* irq0  */

      {0x82, NonHandledInterrupt}, /* irq1  */

      {0x82, NonHandledInterrupt}, /* irq2  */

      {0x82, NonHandledInterrupt}, /* irq3  */

      {0x82, NonHandledInterrupt}, /* irq4  */

      {0x82, NonHandledInterrupt}, /* irq5  */

      {0x82, NonHandledInterrupt}, /* irq6  */

      {0x82, NonHandledInterrupt}, /* irq7  */

      {0x82, NonHandledInterrupt}, /* irq8  */

      {0x82, NonHandledInterrupt}, /* irq9  */

      {0x82, NonHandledInterrupt}, /* irq10 */

      {0x82, NonHandledInterrupt}, /* irq11 */

      {0x82, NonHandledInterrupt}, /* irq12 */

      {0x82, NonHandledInterrupt}, /* irq13 */

      {0x82, NonHandledInterrupt}, /* irq14 */

      {0x82, NonHandledInterrupt}, /* irq15 */

      {0x82, NonHandledInterrupt}, /* irq16 */

      {0x82, NonHandledInterrupt}, /* irq17 */

      {0x82, NonHandledInterrupt}, /* irq18 */

      {0x82, NonHandledInterrupt}, /* irq19 */

      {0x82, NonHandledInterrupt}, /* irq20 */

      {0x82, NonHandledInterrupt}, /* irq21 */

      {0x82, NonHandledInterrupt}, /* irq22 */

   {0x82, TIM4_UPD_OVF_IRQHandler},/* irq23 */

      {0x82, NonHandledInterrupt}, /* irq24 */

      {0x82, NonHandledInterrupt}, /* irq25 */

      {0x82, NonHandledInterrupt}, /* irq26 */

      {0x82, NonHandledInterrupt}, /* irq27 */

      {0x82, NonHandledInterrupt}, /* irq28 */

      {0x82, NonHandledInterrupt}, /* irq29 */

};

解决了以上4个关键点，我们就能很轻松地用C语言实现中断服务了。

同样还是利用ST的开发工具，生成一个C程序的框架，然后修改其中的main.c，修改后的代码如下。另外还要修改stm8_interrupt_vector.c。

编译通过后，下载到开发板，运行程序，可以看到LED在闪烁，或者用示波器可以在LED引脚上看到方波。

  修改后的main.c如下：

//  程序描述：通过初始化定时器4，以中断方式驱动LED闪烁

//            LED接在MCU的GPIO的PD3上

#include "STM8S207C_S.h"

main()

{

  // 首先初始化GPIO

  PD_DDR = 0x08;

  PD_CR1 = 0x08;              // 将PD3设置成推挽输出

  PD_CR2 = 0x00;

  // 然后初始化定时器4                              

  TIM4_IER = 0x00;            // 禁止中断

  TIM4_EGR = 0x01;            // 允许产生更新事件

  TIM4_PSCR = 0x07;           // 计数器时钟=主时钟/128=2MHZ/128

                                                            // 相当于计数器周期为64uS

              TIM4_ARR = 255;             // 设定重装载时的寄存器值，255是最大值

  TIM4_CNTR = 255;            // 设定计数器的初值

                              // 定时周期=(ARR+1)*64=16320uS

  TIM4_CR1 = 0x01;            // b0 = 1,允许计数器工作

                              // b1 = 0,允许更新

                              // 设置控制器，启动定时器

  TIM4_IER = 0x01;            // 允许更新中断

  _asm("rim");                // 允许CPU全局中断

  while(1)                    // 进入无限循环

  {

  }                             

}

// 函数功能：定时器4的更新中断服务程序

// 输入参数：无

// 输出参数：无

// 返 回 值：无

@far @interrupt void TIM4_UPD_OVF_IRQHandler (void)

{

    TIM4_SR1 = 0x00;          // 清除更新标志

    PD_ODR = PD_ODR ^ 0x08;   // LED驱动信号取反

                              //LED闪烁频率=2MHZ/128/255/2=30.63

}                                          

  修改后的stm8_interrupt_vector.c如下：

/*    BASIC INTERRUPT VECTOR TABLE FOR STM8 devices

 *   Copyright (c) 2007 STMicroelectronics

 */

typedef void @far (*interrupt_handler_t)(void);

struct interrupt_vector {

       unsigned char interrupt_instruction;

       interrupt_handler_t interrupt_handler;

};

@far @interrupt void NonHandledInterrupt (void)

{

       /* in order to detect unexpected events during development,

          it is recommended to set a breakpoint on the following instruction

       */

       return;

}

extern void _stext();     /* startup routine */

extern @far @interrupt void TIM4_UPD_OVF_IRQHandler (void);

struct interrupt_vector const _vectab[] = {

       {0x82, (interrupt_handler_t)_stext}, /* reset */

       {0x82, NonHandledInterrupt}, /* trap  */

       {0x82, NonHandledInterrupt}, /* irq0  */

       {0x82, NonHandledInterrupt}, /* irq1  */

       {0x82, NonHandledInterrupt}, /* irq2  */

       {0x82, NonHandledInterrupt}, /* irq3  */

       {0x82, NonHandledInterrupt}, /* irq4  */

       {0x82, NonHandledInterrupt}, /* irq5  */

       {0x82, NonHandledInterrupt}, /* irq6  */

       {0x82, NonHandledInterrupt}, /* irq7  */

       {0x82, NonHandledInterrupt}, /* irq8  */

       {0x82, NonHandledInterrupt}, /* irq9  */

       {0x82, NonHandledInterrupt}, /* irq10 */

       {0x82, NonHandledInterrupt}, /* irq11 */

       {0x82, NonHandledInterrupt}, /* irq12 */

       {0x82, NonHandledInterrupt}, /* irq13 */

       {0x82, NonHandledInterrupt}, /* irq14 */

       {0x82, NonHandledInterrupt}, /* irq15 */

       {0x82, NonHandledInterrupt}, /* irq16 */

       {0x82, NonHandledInterrupt}, /* irq17 */

       {0x82, NonHandledInterrupt}, /* irq18 */

       {0x82, NonHandledInterrupt}, /* irq19 */

       {0x82, NonHandledInterrupt}, /* irq20 */

       {0x82, NonHandledInterrupt}, /* irq21 */

       {0x82, NonHandledInterrupt}, /* irq22 */

    {0x82, TIM4_UPD_OVF_IRQHandler},/* irq23 */

       {0x82, NonHandledInterrupt}, /* irq24 */

       {0x82, NonHandledInterrupt}, /* irq25 */

       {0x82, NonHandledInterrupt}, /* irq26 */

       {0x82, NonHandledInterrupt}, /* irq27 */

       {0x82, NonHandledInterrupt}, /* irq28 */

       {0x82, NonHandledInterrupt}, /* irq29 */

};

                             2010-8-4