STM8S TIM2 输出PWM初始化函数

/*
  * @brief  Simple calulate square  number.
  * @param1  Base number
  * @param2  Exponent number       
  * @retval Number of base^number
  * @author: icerol

*/

unsigned long pow(uint base , uint exponent)
{
    uint temp = 1;
    for(uint i=0; i< exponent; i++)
    {
        temp *= base;
    }
    return  temp;
}

#define TIM2_CH1 0x01
#define TIM2_CH2 0x02
#define TIM2_CH3 0x04
#define F_MASTER 16000000UL
/*
  * @brief  Initial timer2 for pwm output.
  * @param1  PWM output channal, TIM2_CH1 | TIM2_CH2 | TIM2_CH3
  * @param2  PWM putput frequency, Unit: Hz                    
  * @param3-5 PWM duty for CH1-3, range:0-100
  * @retval None
  * @author: icerol

*/
void  timer2_pwm_Init(unsigned char channal, unsigned long hz,unsigned char pwm1, unsigned char pwm2,unsigned char pwm3)
{
    unsigned char pscr=0;
    double tim2_clk;
    for(pscr=0;pscr<0x10;pscr++)
    {
      tim2_clk = F_MASTER/(pow(2,pscr));
      if((tim2_clk/hz)<0xffff)
      {
        break;
      }
    }

    double basecycle = 1000000000/tim2_clk;//us
    double hzcycle=1000000000/hz;
    double arr = hzcycle/basecycle;
    TIM2_ARRH = (unsigned int)(arr)/256;
    TIM2_ARRL = (unsigned int)(arr)%256;
    
    if(channal & TIM2_CH1)
    {
         TIM2_CCMR1 |= 0x70;
         TIM2_CCER1 |= 0x03;      //通道1使能，低电平有效，配置为输出
         TIM2_CCR1H = ((arr*pwm1)/100)/256;
         TIM2_CCR1L = ((arr*pwm1)/100)%256;
    }
    if(channal & TIM2_CH2)
    {
         TIM2_CCMR2 |= 0x70;
         TIM2_CCER1 |= 0x30;      //通道2
         TIM2_CCR2H = ((arr*pwm2)/100)/256;
         TIM2_CCR2L = ((arr*pwm2)/100)%256;
         
    }
   if((channal & TIM2_CH3))
    {
         TIM2_CCMR3 |= 0x70;       //01110000
         TIM2_CCER2 |= 0x03;     //通道3
         TIM2_CCR3H = ((arr*pwm3)/100)/256;
         TIM2_CCR3L = ((arr*pwm3)/100)%256;
         
    }
    TIM2_PSCR = pscr;
    TIM2_CR1 = TIM2_CR1 | 0x01;
    CLK_PCKENR1 = 0x20;
}