STM32F4 Hardware for external clock

[DElec.1]

I want to develop my own PCB using STM32F4. I want to use one external clock (16 MHz). I wonder where I have to connect the clock: OSCIN32-OSCOUT32 (pins 3 and 4) or OSCIN-OSCOUT (HSE) (pins 5 and 6 in STM32F446RET).

I can see in the development board's schematic how there is an empty footprint for X3 (pins 5 and 6) and I don't know if it is using the debugger's clock.

Thanks in advance.

[Jaroslav JANOS]

Hello,

the OSC32 pins are for LSE (32kHz) oscillator, so in your case it is the second pair.

For more information about PCB design guidelines for oscillators refer to AN2867 (https://www.st.com/resource/en/application_note/cd00221665-oscillator-design-guide-for-stm8afals-stm32-mcus-and-mpus-stmicroelectronics.pdf).

Jaroslav

[DElec.1]

Ok, thank you. I did not know if it were necessary to add two capacitors even if you just want the HSE one. I was having some trouble trying to run code and I think it had to do with the oscillator.

[Tesla DeLorean]

The NUCLEO / DISCO boards typically source an 8 MHz crystal based source from the ST-LINK's MCO output.

Watch for solder bridges or zero ohm routing of signal.

​

H​SE should use BYPASS mode for external clocks. Use OSCIN only. Check is source or TCXO expects capacitive loading.

[DElec.1]

In my PCB I use an external 16 MHz crystal oscillator connected directly to the OSCIN-OSC-OUT pins. The schematic includes two capacitors (value = 2 * (Cload - Cstray) = 26 pF). Do I need to set anything special (apart from basic clock configuration, input, freq, etc) in STMCubeIDE?

 

[Tesla DeLorean]

Cross-linking related https://community.st.com/s/question/0D53W00001pIaLwSAK/stm32f4-hardfaulthandler-haltimeout-errors