Timer3 generating 5Hz pulse ?

[antonius]

Dear Member,

How can I generate 5Hz pulse on OC using TIM3 ?

Here is my setting on STM32CubeMx

Thanks

[antonius]

I got PC6 with LED and it's ON, but I don't know what the frequency is,

The setting is :

TIM3->CR1 |= TIM_CR1_CEN;

      HAL_TIM_Base_Start(&htim3);

      HAL_TIM_OnePulse_Start(&htim3,1);

What do I miss here ?

thanks

[antonius]

Please correct me :

The code :

 htim3.Instance = TIM3;

 htim3.Init.Prescaler = 12;

 htim3.Init.CounterMode = TIM_COUNTERMODE_UP;

 htim3.Init.Period = 10000;

 htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV4;

Frequency I got : 2097KHz/(4x10000x12) = 4.3 Hz

??

[S.Ma]

Recap question: What are the clocks available in the chip? MHz? LSI, LSE?

If you want 5 Hz, I would simply use Systick with 1 msec ISR, create a 32 bit milisec counter in RAM as global variable, when this counter reaches 5000, reset it by SW and toggle your output manually.

When time units are so far from kHz, SW implementation maybe good enough.

[Bob S]

htim3.Init.ClockDivision does not do what you think it does. It determines the clock rate on the input filter (if you were using the timer channel as an INPUT, which you are not). It is not another prescaler that divides the timer's input clock to the CNT register, so it has no effect on your output signal.

And is your timer clock really 2.097 MHz?

[antonius]

Yes it is 2.097Mhz

Is this setting equal to 5Hz ?

===

 htim3.Instance = TIM3;

 htim3.Init.Prescaler = 10;

 htim3.Init.CounterMode = TIM_COUNTERMODE_UP;

 htim3.Init.Period = 10000;

 htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV4;

2.097M / *400k

[antonius]

How to to reset in Software ?

[Clive1 (HNL)]

ClockDivision is unrelated to this, it is used by input filters.

Both Prescaler and Period are N-1 numbers

htim3.Init.Prescaler = 2097-1; // 1 KHz

htim3.Init.Period = 200 - 1; // 5 Hz

[S.Ma]

Reset = write 0 on it

uint32_t msec_counter = 0;
 
void My1msecSystickISR(void) // find the corresponding function in the cubemx generated code
{
msec_counter++;
if(msec_counter>=2000) {
 // hello, 0.2 sec elapsed for 5Hz period
LED_Toggle();
msec_counter = 0;
}
}

[antonius]

Abit confuse, is it Prescaler = 2097-1 and Prescaler = 200-1 ?