Do i need extrenal oscilator for STM32H503CBT6

[transistor]

if in the stm32cubeide clock configuration the extrenal oscialtors aren't highlighted it means that i dont need extrenal oscialtor on my custom board?

[mƎALLEm]

Hello @transistor and welcome to the ST community,

That depends on your application. For example, if you plan to use FDCAN interface you need a crystal.

Toggling a LED doesn't need a crystal. You can use HSI as a clock source.

[transistor]

i want to use i2c, pwm so the HSI should be enough?

[mƎALLEm]

If pwm is used for example to control motor speed, no need for crystal in that case. No need for crystal for i2c.