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(stm32f407) USB with fixed vbus

Question asked by acaro.001 on Nov 3, 2014
Latest reply on Nov 3, 2014 by sung.chen_chung
good morning

I 'm doing a project with a custom board , I've been able to make work ethernet, sdio,gpio and serial ports.
 but I  have been troubles with usb port to make run the usb host mode with usb-storage using  stm32cube's libraries.

Right now the usb detects when you connect a USB flash drive , but it is not finished making the enumeration.

I'm afraid of not being able to make work USB, because the value of vbus is set from the power supply to 5v ( as seen in the attached schematic ) .

In the documentation , I found the following sentence :

"On-chip 5 V VBUS generation is not supported. For this reason, a charge pump or, if 5 V are available on the application board, a basic power switch must be added externally to drive
the 5 V VBUS line. The external charge pump can be driven by any GPIO output. This is required for the OTG A-host, A-device and host-only configurations."

Does this mean I need to put a switch to make it works ?

If so, could  I  put a 2N2222 to enable  5v by GPIO?.

PD: I apologize for my english.