FTM0的PWM没有波形出来

烟雨梦 · 发表于 2016-7-29 11:14:19

本帖最后由烟雨梦于 2016-7-29 11:58 编辑

参考官方EPWM的demo,通过ftm0ch1输出PWM控制背光亮度，但示波器一直没有波形出来，都是高电平，代码如下：
void PWM_Init (void)
{
SIM->PINSEL &= ~SIM_PINSEL_FTM0PS1_MASK; //FTM0CH1->PTB3:背光的PWM控制脚
SIM->SCGC |= SIM_SCGC_FTM0_MASK;//open the clock gate
FTM0->SC = 0x0;
FTM0->CONTROLS[1].CnSC = FTM_CnSC_MSB_MASK | FTM_CnSC_ELSB_MASK;
FTM0->CONTROLS[1].CnV  = 1100;
/* update MOD value */
FTM0->CNT = 0;
FTM0->MOD = 9999;
/* set clock source and start the counter */
FTM_ClockSet(FTM0, FTM_CLOCK_SYSTEMCLOCK, FTM_CLOCK_PS_DIV4);
/* enable FTM2 interrupt in NVIC */
NVIC_EnableIRQ(FTM0_IRQn);
/* setup call back function for interrupt */
FTM_SetCallback(FTM0, PWM_Task);
FTM_EnableOverflowInt(FTM0);
}
uint16_t u16ChV_old, u16ChV_new;
void PWM_Task(void)
{
static uint16_t u16count;
static uint8_t u8DirMark;

// clear the flag
FTM_ClrOverFlowFlag(FTM0);

if(100 == u16count)
{
      u16count = 0;
      u16ChV_old = FTM0->CONTROLS[1].CnV;
      if(!u8DirMark)
      {
         u16ChV_new = u16ChV_old + 200;
         if(u16ChV_new >= FTM0->MOD)
         {
            u16ChV_new = FTM0->MOD - 200;
            u8DirMark  = 1;
         }
         else
         {
         }
      }
      else
  {
         u16ChV_new = u16ChV_old - 200;
         if(u16ChV_new < 200)
         {
            u16ChV_new = 200;
            u8DirMark  = 0;
         }
         else
         {
         }
      }
      // update the channel value
      FTM_SetChannelValue(FTM0, FTM_CHANNEL_CHANNEL1, u16ChV_new);
}
else
{
      u16count++;
}
}
不只是哪里配置还有问题，求帮助