HAL_Delay(1); takes 2ms

If you want something that can resolve better, use a TIM that clocks faster, and read the TIMx->CNT

Code may also be interrupted

To measure or wait a precise duration, you may need a dedicated stopwatch, sharing a always running wallclock won't be the same...

waclavek.jan,Tesla DeLorean, S.Ma :

But I'm not interested in accuracy. The time is always accurate, just always +1ms, because as I found out, the function automatically increments the variable at the beginning.

__weak void HAL_Delay(uint32_t Delay)
{
 uint32_t tickstart = HAL_GetTick();
 uint32_t wait = Delay;
 
 /* Add a freq to guarantee minimum wait */
 if (wait < HAL_MAX_DELAY)// allways add uwTickFreq (1)
 {
 wait += (uint32_t)(uwTickFreq);
 }
 
 while((HAL_GetTick() - tickstart) < wait)
 {
 }
}

For values in hundreds of milliseconds it is of course not important, but for 1ms it does 100%. And that caused me a problem that I only discovered by using a logic analyzer.

Of course, it is a weak function that I can override according to my needs, but I was more interested in the reason why it is so.

Sure, the comment says that it should guarantee at least a minimal delay, but it can certainly be better:

 /* Add a freq to guarantee minimum wait */
 if (wait < 1)
 {
 wait += (uint32_t)(uwTickFreq);
 }

Or am i wrong?

I tried to answer ecactly this in the article I linked to above.

JW