Changing duty cycle for TIM8

[brandonchan2001]

Posted on April 08, 2011 at 00:20

Changing duty cycle for TIM8

[mehmet.karakaya]

Posted on May 17, 2011 at 14:30

void PWMinit(void){

  /* Time Base configuration */

  TIM_TimeBaseStructure.TIM_Prescaler = 0;

  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseStructure.TIM_Period = 7200;

  TIM_TimeBaseStructure.TIM_ClockDivision = 0;

  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

  TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);

  /* Channel 1, 2,3 and 4 Configuration in PWM mode */

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Timing;

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;

  TIM_OCInitStructure.TIM_Pulse = 200;

  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

  TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;

  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;

  TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Set;

  TIM_OC1Init(TIM8, &TIM_OCInitStructure);

  TIM_OC2Init(TIM8, &TIM_OCInitStructure);

  TIM_OC3Init(TIM8, &TIM_OCInitStructure);

  

  TIM_CCPreloadControl(TIM8, DISABLE);

  /* TIM1 counter enable */

  TIM_Cmd(TIM8, ENABLE);

  /* Main Output Enable */

  TIM_CtrlPWMOutputs(TIM8, ENABLE);

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and in the main loop

        TIM8->CCR1= 500;

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this code is working with my application

I looked at the supplied example code that uses the TIM3 timer and was able to change the TIM->CCR1 register inside a while loop in order to change the PWM duty cycle while the MCU is running. However, when I tried to do the same with TIM8, the duty cycle seems to stay constant at the initial TIM->CCR1 value that it was initialized with (duty cycle remains constant). Are there special conditions for TIM8 that I should be aware of when dealing with TIM8 specifically?

Any help would be greatly appreciated thanks!