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Problem with Timing

Question asked by shrestha.durgesh on Jan 4, 2012
Latest reply on Dec 27, 2013 by Clive One
PROBLEM: Timer interrupt is entered immediately in the beginning and not in the desired timing period.
The objective is to enter a service routing of TIM4 with a timing of every 10 sec, clock is 72Mhz:

  TIM_TimeBaseStructure.TIM_Period = 65535;
  TIM_TimeBaseStructure.TIM_Prescaler = 39999;
  TIM_TimeBaseStructure.TIM_ClockDivision = 1;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

  // OCMode Active configuration: Channel1
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Active;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 18000;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;

  TIM_OC1Init(TIM4, &TIM_OCInitStructure);
  // interrupt on update
  TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE);

  TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);

  TIM_ARRPreloadConfig(TIM4, ENABLE);
  // TIM4 enable counter

The interrupt service routine is entered immediately after the beginning and not after 5 seconds.

I would be happy if someone could help me on this.