Configuring clocking for STM32F479VI in order to run CDC_standalone and facilitate USB_HS_IN_FS.

[JSkar.1]

I'm working with an STM32F479VI on a custom PCB. I've already set the HSE_VALUE to the frequency of my external Osc. I've been told however, that in order to use HS_IN_FS I also need to configure the PLL. The readme.txt also says something about setting a "USBCLK" variable, which I can't find. Because of how the MCU is broken out on the custom PCB, I have to use pins PB14 and PB15, the USB_OTG_HS pins, for my USB interface.

#1 Can I run HS_IN_FS without an external ULPI PHY chip?

#2 There are a lot of variables with "PLL" in them. Which ones do I set and where (I'm guessing in system_stm32f4xx.c)?

#3 Do I need to install any drivers on Windows 10 or 11 before the USB com port will enumerate, provided everything else is working?

I've been reviewing the documentation but because I'm using an example app that I didn't build up myself, I'm finding the learning curve a bit staggering and I've got a deadline coming up.

Any help would be greatly appreciated, thanks.

[TDK]

> #1 Can I run HS_IN_FS without an external ULPI PHY chip?

Yes, you can run the USB_OTG_HS peripheral in in full speed mode by using the internal FS PHY.

> #2 There are a lot of variables with "PLL" in them. Which ones do I set and where (I'm guessing in system_stm32f4xx.c)?

Run CubeMX with your chip for a good visualization of the clock scheme. You need to ensure the "48 MHz" clock is 48 MHz, which typically comes off of PLL1Q.

 

Typically clock settings are set in SystemClock_Config().

> #3 Do I need to install any drivers on Windows 10 or 11 before the USB com port will enumerate, provided everything else is working?

In theory, no. In practice, I have has to do so on some Win10 computers.

[JSkar.1]

Thanks for the response. Valuable advice, especially that about the clocking tree.