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waclawek.jan
waclawek.janBest answer
Super User
December 23, 2019

> it looks like with each delay, it lasts 1ms more!

This is how HAL_Delay() works - it provides you a *minimum* N ms delay.

It looks at a timer which ticks continuously once in 1ms. So, when you call it, it looks at that timer's value, say it's K, and then waits until that timer rolls over from K+N to K+N+1.

If you happen to call it just moments before it rolls over from K to K+1, the delay will be just slightly longer than N ms. If you happen to call it slightly after it rolls over from K-1 to K, the delay will be just slightly shorter than N+1 ms.

JW

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8 replies

oeliks
oeliks
Associate III
December 22, 2019

Well its worst thing to do if you want to generate pulse. For me it produced waveform with randomly changing period.

​

Set scope to capture single event, and set and reset pin once, not in loop. Also check clocks.​

​

Try to use timer as pwm or just to toggle pin.​

Tesla DeLorean
Tesla DeLorean
Guru
December 22, 2019

Make sure HSE_VALUE reports 8 MHz and not 25, and that the PLL and clock settings are correct.​

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Ala
AlaAuthor
Senior
December 23, 2019

Dear clive1

can you tell me in details what should I do?

should I set the HSE to Crystal/Ceramic Resonator?

what should I do in the CubeMX clock settings? like in the below image?0690X00000Buu7xQAB.png

oeliks
oeliks
Associate III
December 23, 2019

First enable HSE, in cubemx system RCC->HSE crystal resonator. Then go to clocks menu (image above). Change input frequency from 25 to 8, and check​ HSE option. Change HCLK to desired core clock and allow cubemx to recalculate all prescalers.

Ala
AlaAuthor
Senior
December 23, 2019

Dear Oeliks

I did as you said and I set the HCLK to 16, still it doesn't work

it looks like with each delay, it lasts 1ms more!

for example when I set HAL_Delay(2), for the pin PD12 to remain SET, it remains SET for 3ms!!!

WHY GUYS????

oeliks
oeliks
Associate III
December 23, 2019

Sorry, cant help more.

​

For precise time base I use timers and interrupts. For no critical things I use delay. Mabey Clive1 can help more.​

waclawek.jan
waclawek.janBest answer
Super User
December 23, 2019

> it looks like with each delay, it lasts 1ms more!

This is how HAL_Delay() works - it provides you a *minimum* N ms delay.

It looks at a timer which ticks continuously once in 1ms. So, when you call it, it looks at that timer's value, say it's K, and then waits until that timer rolls over from K+N to K+N+1.

If you happen to call it just moments before it rolls over from K to K+1, the delay will be just slightly longer than N ms. If you happen to call it slightly after it rolls over from K-1 to K, the delay will be just slightly shorter than N+1 ms.

JW

    Ala
    AlaAuthor
    Senior
    December 23, 2019

    THANKS Dear waclawek.jan!

    It was a big help!:folded_hands:

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