【原】如何配置STM32的USB时钟？

若外部时钟为25MHz，故 HSE_VALUE 为25M

PLL_VCO = HSE_VALUE / PLL_M * PLL_N

                = 25M / 25 * 336

                = 336M

USB Clock = PLL_VCO / PLL_Q

                 = 336M / 7

                 = 48M

SYSCLK = PLL_VCO / PLL_P

             = 336 / 2

             = 168M