about stm32 hardware design

[ranganatennakoon]

The stm32F103XX needs 2 oscillators. 8MHz is main one and 32KHz for RTC. If I don't use the RTC functions then adding the 32KHz oscillator is not essential right?

thanks

[gamalot]

Yes, you are right, in fact both external crystals are optional and the STM32 can run without both of them.

[JohanH]

If you use USB, the internal clock doesn't have good enough tolerance for the USB specification, although it might work in practice, but isn't guaranteed.

[jordannedev]

https://www.st.com/resource/en/application_note/an2586-getting-started-with-stm32f10xxx-hardware-development-stmicroelectronics.pdf
Here you will find all the basic information about the peripheral components that are required for the MCU. Personally, in my projects, I connect only the HSE crystal oscillator.

[ajb]

If you use USB, the internal clock doesn't have good enough tolerance for the USB specification, although it might work in practice, but isn't guaranteed.

I don't know about these ST parts in particular, but some MCUs can use the USB SOF to discipline an internal oscillator, to allow USB to work without a more accurate local clock.  But in general, yes, internal RC oscillators are much lower accuracy and stability and might not be good enough for sensitive applications, including UART links, so you'll have to look at the datasheet and do the math.

[ranganatennakoon]

If I don't use the RTC functions then adding the 32KHz oscillator is not essential right?

[thm_w]

If I don't use the RTC functions then adding the 32KHz oscillator is not essential right?

Yes, gamalot answered this above.