STM32F746 CubeMX clock not reporting correctly?

Posted on October 25, 2017 at 18:38

I'm using an STM32F746VGT6 microcontroller configured from STM32CubeMX for all the clocks and I'm getting roughly 220% higher clock rates reported for SystemCoreClock when compiled. For instance I have an HSE crystal at 11.2896MHz with the following main PLL settings:

PLLM /11

PLLN *234

PLLP /2

PLLQ /5

I have selected HSE for PLL source and PLLCLK as System Clock Source. Doing that in STM32CubeMX yields 120.080291MHz.

However, after SystemClock_Config(), SystemCoreClock = 265909059.

Due to that discrepancy, the microcontroller thinks it's working 220% faster than it actually is so all my timings are off by that much.

My first clue was when I configured SAI_BlockA1 and measured MCLK to be double than expected.  Then testing an output with HAL_Delay(50) gave me actual delay of 110ms.

Has anyone else seen this issue and what could be the problem here? Thanks for any insight.

#stm32f746 #stm32cubemx