HAL_Delay - out by 1ms ?

[gil_dobjanschi]

Hello,

I am using HAL2 and wrote the basic code below:

  while (1) {
    HAL_GPIO_TogglePin(LD1_PORT, LD1_PIN);
    HAL_Delay(1);
  }

I looked at the pin with an oscilloscope and I see that the signal stays 2ms low and 2ms high. If I change the code to HAL_Delay(0) I get a signal that stays low 1ms and high 1ms. It's as if the delay is actually the HAL_Delay parameter plus 1ms.

Any explanation?

-Gil

[Andrew Neil]

Have you checked that your system clock is actually what you expect ?

eg, by routing to MCO.

[Andrew Neil]

Bug HAL_delay() off by 1ms

So try some delays significantly longer than 1ms ...

[TDK · Accepted solution]

> It's as if the delay is actually the HAL_Delay parameter plus 1ms.

That's exactly what it does here. Since the tick resolution is 1ms. it needs to have a buffer of 1ms to guarantee the minimum wait time. The argument is the minimum delay.

HAL_Delay(1) will delay between 1-2 ms. If you call it repeatedly in a tight loop, it will delay exactly 2ms on average.

stm32f4xx-hal-driver/Src/stm32f4xx_hal.c at eaa636c7be367100405b2109023c6dbb12429b98 · STMicroelectronics/stm32f4xx-hal-driver

If you need more precision, consider overloading HAL_Delay with your own more precise code. Using a TIM or the DWT->CYCCNT is popular.