CubeIDE Clock Editor won't allow HSE selection with external clock

[Andrew Neil]

STM32CubeIDE Version: 1.13.0; Build: 17399_20230707_0829 (UTC).

It seems that the IDE greys-out the options to use HSE: 

Unless both PF0 is configured as RCC_OSC_IN and PF1 is configured as RCC_OSC_OUT:

Surely, it should be possible to use HSE when only PF0 is configured as RCC_OSC_IN - as shown in the Reference Manual:

[TDK · Accepted solution]

You have to enable bypass mode under RCC. Just reserving the pin (i.e. the pin is yellowed out) isn't enough.

[Andrew Neil]

Ah, right - that does it.

Seems a bit clunky, though.

The 'resolve clock issues' didn't suggest this if I selected HSE and then switched back to just PF0 in clock mode.

And this is the IOC generated specifically for the F0-Disco - which, by default, has no crystal fitted and gets its clock from the on-board STLink.

[Andrew Neil]

It does manage to automatically set 'Crystal/Ceramic resonator' when you configure both PF0 and PF1 - so why can't it automatically set 'Bypass' when you only configure PF0 ?

🙄

[TDK]

Interestingly, on the F429, if you assign PF0 and PF1 to the oscillator it does not automatically set the HSE selection to crystal. But on the F051 it does. I doubt behavior like this is deliberately managed at the individual chip level. Just sort of works the way the machinery is set up.