STM32F407 Timer Frequency

AlexSmart · ‎2015-03-09

Posted on March 09, 2015 at 17:56

I can't understand how come TIM1 frequency is 42 MHz.

Here is my config:

12 MHz HSE -> 168 MHz PLLCLK (MCO/4 = 42 MHz, checked)

APB1 prescaler = 4

APB2 prescaler = 2

so TIM1, as it clocked from APB2 x 2 frequency should be 168 MHz.

But output (GPIO^PIN in update interrupt) generates 0.21 MHz frequency

0.21x100x2 = 42MHz.

RCC_PCLK1Config(RCC_HCLK_Div4);

RCC_PCLK2Config(RCC_HCLK_Div2);

RCC_HCLKConfig(RCC_SYSCLK_Div1);

TIM_TimeBaseStructure.TIM_Period = 99;

TIM_TimeBaseStructure.TIM_Prescaler = 0;

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

#tim #stm32

Tesla DeLorean · ‎2015-03-09

Posted on March 09, 2015 at 19:43

Odd, what do you see with this?

TIM_TimeBaseStructure.TIM_Period = 999;
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

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waclawek.jan · ‎2015-03-09

Posted on March 09, 2015 at 19:43

> (GPIO^PIN in update interrupt)

OK, so how long (in seconds or microseconds) does the pin remain in LOW state?

And how long does it remain in HIGH state?

The frequency is inverse of the WHOLE period, i.e. tLOW + tHIGH.

JW

AlexSmart · ‎2015-03-10

Posted on March 10, 2015 at 10:24

Thank you so much!

Problem was in

TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;