Question about using HSE clock on STM32 NUCLEO-F446RE board

[ragawendrareddyh]

Hello everyone,

I am new to STM32 and recently purchased the STM32 NUCLEO‑F446RE development board to start learning microcontrollers.

While studying the clock configuration, I saw the option to use HSE (High Speed External oscillator). Since I am a beginner, I searched about it and found suggestions saying that I may need to add an external crystal and capacitors and solder them onto the Nucleo board.

However, I am not sure whether this is actually required for this board. I also read that the Nucleo board might provide an 8 MHz clock from the onboard ST-LINK via MCO, which can be used as the HSE source.

So I would like to clarify:

1. Do I need to add an external crystal oscillator to use HSE on this board?

2. If yes, what crystal frequency and capacitor values are recommended?

3. Can anyone suggest reliable components or purchase links for the required oscillator?

I would appreciate any guidance. Thank you!

[TDK · Accepted solution]

By default, the chip is set up to use HSE in BYPASS mode. This takes an 8 MHz which is produced by the ST-Link chip and uses that as a clock. This is derived from a crystal so it is a stable clock source. You should generally use this.

If you want to use a crystal, yes you will need to add it and disconnect the MCO output from the st-link by removing a resistor. The instructions and recommendations for the crystal are in the user manual.

https://www.st.com/resource/en/user_manual/um1724-stm32-nucleo64-boards-mb1136-stmicroelectronics.pdf

[ragawendrareddyh]

Thank you for the information.