USB 上拉电阻 VBUS
USB 上下拉电阻问题内部集成了上下拉电阻，无需外部添加，至于与VBUS之间关系待验证。https://github.com/jeanthom/DirtyJTAG/issues/10https://github.com/MayaPosch/Nodate/blob/5252337dbe0aed25dcb9da7f25c9dc428238e139/arch/stm32/arduino/stm...
