Hi all,
I've created a new default project for the STM32N6 Discovery Kit, and set up a simple blinking application using the BSP LED functions.
/* USER CODE BEGIN 2 */
BSP_LED_Init(LED_GREEN);
while(1)
{
HAL_Delay(1000);
BSP_LED_Toggle(LED_GREEN);
}
/* USER CODE END 2 */
I've noticed that in the Application, HAL_Delay() runs roughly 2× too fast. For example, HAL_Delay(1000) only delays for ~500 ms. I can see this because the LED is blinking too quickly.
In this Application, TIM2 is used as the timebase source (I presume because of ThreadX using SysTick).
I looked at the TIM2 setup in HAL_InitTick() (inside stm32n6xx_hal_timebase_tim.c). The relevant snippet is:
/* Compute TIM2 clock */
uwTimclock = HAL_RCC_GetPCLK1Freq();
/* Compute the prescaler value to have TIM2 counter clock equal to 1MHz */
uwPrescalerValue = (uint32_t) ((uwTimclock / 1000000U) - 1U);
/* Initialize TIM2 */
htim2.Instance = TIM2;
/* Initialize TIMx peripheral as follow:
* Period = [(TIM2CLK/1000) - 1]. to have a (1/1000) s time base.
* Prescaler = (uwTimclock/1000000 - 1) to have a 1MHz counter clock.
* ClockDivision = 0
* Counter direction = Up
*/
htim2.Init.Period = (1000000U / 1000U) - 1U;
htim2.Init.Prescaler = uwPrescalerValue;
htim2.Init.ClockDivision = 0;
htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
From the debugger:
uwTimclock = 200 MHz (APB1 peripheral clock)
TIM2 registers for Period and Prescaler are set as expected
HAL_IncTick() is only called once per TIM2 interrupt
So all of the math kind of seems correct (I think?), but despite this, uwTick increments much too quickly, causing HAL_Delay() to run faster than expected.
Observations:
In my own project, the tick was 4× too fast
In this default project, it is 2× too fast
In the FSBL, HAL_Delay() is accurate
Has anyone encountered this behavior? Could this be related to the TIM2 clock configuration or some STM32N6-specific behavior with APB1 timers?
Thanks in advance!
