The STM32F303xC datasheet says:
No external termination series resistors are required on USB_DP (D+) and USB_DM (D-), the matching impedance is already included in the embedded driver.
In consequence, R21 and R22 should be populated with 0 Ω resistors.
The STM32F303xC datasheet says:
No external termination series resistors are required on USB_DP (D+) and USB_DM (D-), the matching impedance is already included in the embedded driver.
In consequence, R21 and R22 should be populated with 0 Ω resistors.