H755ZI-Q SysTick Not firing for either core

Ascii_Guy · ‎2025-08-04

Hi,

I'm not new to STM32 frimware, however, this is my first with H755. I have uploaded a simple LED flash project to both cores. The LED timing is based on uwTick, but Systick is not firing!

Green LED via M4, Yellow LED via M7.

If I change the code M4 to:-

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    GPIOE->ODR ^= 0x02;
    /* USER CODE END WHILE */
    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */

And code for M7 to:-

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    GPIOB->ODR ^= 0x01;
    /* USER CODE END WHILE */
    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

Stepping through the program manually, both LEDs toggle as expected.

When I run without breaks, the Green LED toggles full speed (as expected), however, the Yellow LED toggles about once per second!

I created the project from CubeIDE - just the basic project from the Nucleo-H755ZI-Q template.

Win11, Cube Version:-

Version: 1.19.0

Build: 25607_20250703_0907 (UTC)

STM32 FW_H7 1.12.1

Can anyone help?

Thanks AG