how to configure EXTI ?

Posted on May 17, 2011 at 14:14

thank you I enabled AFIO clock and it worked

in order not to open a new topic I have another question here

I want a timer to tick between 1 Hz  and 10 KHz

is there an example for this ? ( how to calculate prescaler and reload register for this job ? )

Posted on May 17, 2011 at 14:14

You must enable the AFIO clock, and the GPIOC clock.

The EXTI registers are within the AFIO unit, chances are you haven't enabled it.

Posted on May 17, 2011 at 14:14

With SYSTICK. provided your main clock is within range.

SysTick_Config(SystemCoreClock / 10); // 10 Hz

SysTick_Config(SystemCoreClock / 10000); 10 KHz

  // TIM4CLK = 36 MHz

  x = 100; y = 36; // Clock at 1 MHz (36 MHz/36), 100 ticks, 10 KHz

or

  x = 1000; y = 36000; // Clock at 1 KHz (36 MHz/36000), 1000 ticks, 1 Hz

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

  /* Time base configuration */

  TIM_TimeBaseStructure.TIM_Period = (x - 1); // 1-65536

  TIM_TimeBaseStructure.TIM_Prescaler = (y - 1); // 1-65536

  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; // 1,2 or 4 for tDTS

  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

Posted on May 17, 2011 at 14:14

in order not to open a new topic I have another question here

 

 

I want a timer to tick between 1 Hz  and 10 KHz

 

is there an example for this ? ( how to calculate prescaler and reload register for this job ? )

 

I think I've posted examples before.

The basic formula, f = CLK / (p * q), where Prescaler = (p - 1), Period = (q - 1), and where q = less than 65536

I'll post some other examples in a bit.