Stm32f429zi RCC setup

[jared212]

Hi!

I'm using Nucleo-f429zi board and my trying to configure it to read and write data over modbus RTU (RS485)

and i'm using keil uvision 5 to program. I have referred some videos and post on how to configure STM32 and its USART port for modbus communication but when I try to configure RCC in STM32cubeMX i get a error highlighting

master clock 1 and when i hover mouse courser over it, it says conflict with usb.

can someone explain me how to solve this error and why i'm facing this issue? 

[Pavel A.]

Is the Master clock output (MCO) output needed for the project? If not, ignore this and keep going. It is not a real conflict.