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

[Hl_st]

Timer settings seems to be right. Have you done clock configuration in CubeMX? Please check if time clock (APB1 Timer clocks) is really 72 MHz.

Set CKD in (TIMx_CR1) as 00 should be correct

[Andrew Neil]

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@Hl_st wrote:

 check if time clock (APB1 Timer clocks) is really 72 MHz.

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+1

@Ash1 If in doubt, route the clock to one of the MCO pins, and measure it; eg, on an oscilloscope.

[Tesla DeLorean]

Sounds like you're clocking at 100 or 108 MHz, not 72

Check your PLL and HSE relationships 

[Ash1]

hi

Can you suggest me a code in which there is generated interrupt using any timer

[SofLit]

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@Ash1 wrote:

hi

Can you suggest me a code in which there is generated interrupt using any timer

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Time base with interrupt:

https://github.com/STMicroelectronics/STM32CubeF4/blob/master/Projects/STM324xG_EVAL/Examples/TIM/TIM_TimeBase

PS: No ioc file available for this example.

[Andrew Neil]

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@Ash1 wrote:

Can you suggest me a code in which there is generated interrupt using any timer

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The code posted by @SofLit in the very first reply !

[Ash1]

Hi

I have recheked my configuration and found it was 84mhz timer clock instead of 72Mhz

so for 10 second I am loading 0x98967F in ARR and 83 i have loaded in PSC register but still timer is generating UIF flag sometimes in 7 seconds 4 seconds 2 seconds .can you help me Why I am facing this irregular intervals of setting UIF flag

Note :Do i have to set URS bit also in CR1 will it effec

[Tesla DeLorean]

You should be able to set it up once, and it will keep knocking at the right period.

Do you change anything in the interrupt handler or callback?

If you have SysTick running you could record HAL_GetTick() on the update interrupt, perhaps print there, or in your main() loop, or toggle a GPIO.

At long periodicity it will be a challenge to scope

I tend to code directly in HAL, without the code generators, it's not hard to set up the TIM in timebase mode. Soflit's code should suffice.

For long term you need 32-bit like TIM2 / TIM5, or you can use 16-bit or SysTick to count off smaller periods, or count-down a queue/list of software timers, say millisecond counts.

[Ash1]

hi 

To toggle any GPIO pin what parameters I should select e.g registers values .

like values for this register to use any pin as GPIO toggling

MODER; /**< @brief MODER Register */

OTYPER; /**< @brief OTYPER Register */

OSPEEDR; /**< @brief OTYPER Register */

PUPDR; /**< @brief PUPDR Register */

LCKR; /**< @brief LCKR Register*/

AFRL; /**< @brief AFRL Register*/

AFRH; /**< @brief AFRH Register*/

Note: For your reference I am sharing logic analyzer picture in which i have connected to PD15 which is my LED also ,problem what I am facing I am able to toggle LED every one sec but at my logic analyzer it is showing low at all time . but LED is toggling

[gbm · Accepted solution]

Read The Fine Document - the Reference Manual, GPIO section. The only register needed for simple output setup is MODER; you don't need to touch the others.

Regarding the timer setup: why should you calculate the values? Leave it to the compiler. For simple timebase setup:

#define TIMCLK_FREQ 84000000u

#define TIM_PERIOD_us 1000u

TIMx->PSC = TIMCLK_FREQ / 1000000u - 1;

TIMx->ARR = TIM_PERIOD_us - 1;