Calculate ARR value for Timer TIM2, TIM3 in STM32F407

[Ash1]

Hi

Can you tell me how I can calculate a value for ARR for timer 2(32bit timer) and timer3(16bit timer)

I am using STM32F407 APB1 timer clock is 12MHz prescaler is 6

[mƎALLEm]

Hello,

For which purpose? time base?

Inspire from:

https://github.com/STMicroelectronics/stm32f4xx-hal-driver/blob/4ae1c83b8aa574042fee644688d406b2429a95d6/Src/stm32f4xx_hal_timebase_tim_template.c

 

 

 /* Get clock configuration */
 HAL_RCC_GetClockConfig(&clkconfig, &pFLatency);

 /* Get APB1 prescaler */
 uwAPB1Prescaler = clkconfig.APB1CLKDivider;

 /* Compute TIM6 clock */
 if (uwAPB1Prescaler == RCC_HCLK_DIV1)
 {
 uwTimclock = HAL_RCC_GetPCLK1Freq();
 }
 else
 {
 uwTimclock = 2 * HAL_RCC_GetPCLK1Freq();
 }

 /* Compute the prescaler value to have TIM6 counter clock equal to 1MHz */
 uwPrescalerValue = (uint32_t) ((uwTimclock / 1000000U) - 1U);

 /* Initialize TIM6 */
 TimHandle.Instance = TIM6;

 /* Initialize TIMx peripheral as follow:
 + Period = [(TIM6CLK/1000) - 1]. to have a (1/1000) s time base.
 + Prescaler = (uwTimclock/1000000 - 1) to have a 1MHz counter clock.
 + ClockDivision = 0
 + Counter direction = Up
 */
 TimHandle.Init.Period = (1000000U / 1000U) - 1U;
 TimHandle.Init.Prescaler = uwPrescalerValue;
 TimHandle.Init.ClockDivision = 0U;
 TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;
 TimHandle.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
 status = HAL_TIM_Base_Init(&TimHandle);

 

See also the application note AN4013 "Introduction to timers for STM32 MCUs " / section 2.2 Time base generator

 

[Andrew Neil]

See also the Timer section in the Reference Manual for your chip.

 

And: https://wiki.st.com/stm32mcu/wiki/Getting_started_with_TIM

 

And Application note AN4776, General-purpose timer cookbook for STM32 microcontrollers

 

ST Videos on timers: https://www.youtube.com/@stmicroelectronics/search?query=timer

 

Many 3rd-parties also have resources; eg, https://www.digikey.co.uk/en/maker/projects/getting-started-with-stm32-timers-and-timer-interrupts/d08e6493cefa486fb1e79c43c0b08cc6

 

[Hl_st]

Hello,

can you show what should be the purpose of each timers?

If you have timer clock on 12 MHz and prescaler is 6 the timer counter will be counted with frequency

12 MHz / (6+1) = 1.71 MHz. ARR register defines when timer counter will be reloaded. Frequency of reloading the timer counter is calculated as: 1.71 MHz / (ARR+1) in this case.

[Ash1]

Hi

I will again refreshed my query my APB1 timer clock is 72Mhz so does it mean my timer are running on 72Mhz?

prescaler value which I said earlies it was CAN prescaler so plz ignore previous query.

second I want to create a delay like 10millisec 100millisec e.g every 10ms interrupt will generate.

for explanation you can take any 10ms ,100ms

note: at the time of Timer_Initialization I loaded ARR value with 0xFFFFFFFF and Counter value with 0x00000000

auto preload is disabled.

and at runtime time I am want to change ARR value with desired value I am using upcounter. so i want to know what will prescaler value and method to create a delay.

[Andrew Neil]

---

@Ash1 wrote:

my APB1 timer clock is 72Mhz so does it mean my timer are running on 72Mhz?

---

See the Reference Manual - that will show how the timer's counter is clocked.

See also the clock configuration in CubeMX.

 

---

@Ash1 wrote:

second I want to create a delay like 10millisec 100millisec e.g every 10ms interrupt will generate.

---

So that's a Timebase - as illustrated by @mƎALLEm