# Inconsistent timeout in xSemaphoreTake

**URL:** <https://forums.freertos.org/t/inconsistent-timeout-in-xsemaphoretake/14164>\
**Category:** Kernel\
**Created:** [January 6, 2022, 3:50pm UTC](https://forums.freertos.org/t/inconsistent-timeout-in-xsemaphoretake/14164 "2022-01-06T15:50:09Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![sirac](https://avatars.discourse-cdn.com/v4/letter/s/a6a055/32.png) [@sirac](https://forums.freertos.org/u/sirac)\
**Post date:** [January 6, 2022, 3:50pm UTC](https://forums.freertos.org/t/inconsistent-timeout-in-xsemaphoretake/14164/1 "2022-01-06T15:50:09Z")

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- Version : V10.3.1
- Port : stm32l4

I have a weird behaviour with xSemaphoreTake and a binary semaphore. I call a function indefinitly and this function call xSemaphoreTake several times. Nothing give the semaphore so the function is use only like a delay (of course, this isn’t the goal of my code). The first call of xSemaphoreTake lead always to a fail in less than the timeout specified.

Here the function I call indefinitly :

```auto
int32_t Ad7124ReadDataWithIrq(Ad7124_TypeDef *dev, int8_t *data, uint8_t chCount){
	for(uint8_t i = 0; i< chCount;i++){

		HAL_GPIO_WritePin(GPIOC, GPIO_PIN_8, GPIO_PIN_SET);
               
               //if i == 0 => this function exit after less than 1ms (between 200 or 900µs)
		xSemaphoreTake(_BspExtAdcReadySemaphore, pdMS_TO_TICKS(1));

		HAL_GPIO_WritePin(GPIOC, GPIO_PIN_8, GPIO_PIN_RESET);
                //This one is always good
		xSemaphoreTake(_BspExtAdcReadySemaphore, pdMS_TO_TICKS(1));
	}
	return(0);
}

```

I use GPIOC8 to measure the timeout with an oscilloscope.  
I have only 1 task and no isr (only timer1 for tick). This bug occurs doesn’t matter chCount value.  
If chCount = 1, the timeout is always 560µs.

Someone have an idea ?

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<div class="post-metadata">

**Author:** ![richard-damon](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/richard-damon/32/38_2.png) [@richard-damon](https://forums.freertos.org/u/richard-damon)\
**Post date:** [January 6, 2022, 4:04pm UTC](https://forums.freertos.org/t/inconsistent-timeout-in-xsemaphoretake/14164/2 "2022-01-06T16:04:30Z")

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Remember that a time-out value of 1 means until the next tick interrupt, which will normally be less than the tick period unless you know that a tick just occurred. That is the nature of ticks, they have a granularity of the period. If you want at least one tick period you need to wait for 2 ticks.

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<div class="post-metadata">

**Author:** ![sirac](https://avatars.discourse-cdn.com/v4/letter/s/a6a055/32.png) [@sirac](https://forums.freertos.org/u/sirac)\
**Post date:** [January 7, 2022, 6:47am UTC](https://forums.freertos.org/t/inconsistent-timeout-in-xsemaphoretake/14164/3 "2022-01-07T06:47:38Z")

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This is totally obvious, thank you for you time.