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USB OTG FS in stm32f4 not detected by PC

Question asked by viswanathan.sree.001 on Sep 28, 2017
Latest reply on Apr 2, 2018 by Qin Zhang

I have designed a custom board with stm32f407 mcu and included USB OTG FS functionality in it. For USB OTG I have followed similar schematic like the one shown for stm32f407 discovery board. I downloaded a firmware program that utilizes the USB VCP demo code provided by ST. However my windows pc does not seem to connect properly with my board. It is able to detect the device but shows it as unknown USB device.

 

I tested the hw and could not find any obvious error( shorted pins etc).  when I connect the otg cable to PC, the board VBUS light turns ON and i measured it to be 5V, ID Pin(PA10) has 3v and immediately as I connect the device with the PC the D+(PA12) and D-(PA11) pins seem to have some data flowing but it lasts only for few seconds.

 

The same code works well in stm32f407 discovery board. Am I missing something here ? I have never designed USB in my boards before hence new to this. How do I start debugging it? If the PC identifies my device as unknown USB device what are the possible hardware issue I should be looking into? 

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