STM32F4 Clock Config with USB?

[eric5709]

Posted on March 06, 2016 at 16:03

Hello,

When adding a USB CDC Device to my project using CubeMX I am getting an error in the clock configuration tab saying that the source of the clock has to be external? If USB is removed then there is no error. Attached is the image I am seeing. 

[Tesla DeLorean]

Posted on March 06, 2016 at 16:25

The HSI does not meet accuracy specifications required by USB and CAN, which have clocking tolerances.

Also seem to recall you need the PLL/VCO to hit specific frequencies in the 192-432 MHz range.