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ahansen
ahansen
Associate
August 1, 2018
Question

Automatically reconnect to USB device after programming

  • August 1, 2018
  • 3 replies
  • 1055 views

Hi.

I'm currently trying to develop a simple USB (CDC) application with an STM32 MCU that is configured using CubeMX. So far I have managed to make the device send some text message to my host machine which is displayed using a serial terminal program. But, I have noticed, that after programming new firmware to the target, I must physically disconnect and connect my board in order to reestablish the connection. I was wondering if there was a better way to do this ?

Best Regards,

abaldur

This topic has been closed for replies.

3 replies

Pavel A.
Pavel A.
Super User
August 1, 2018

Disable the USB controller and wait several seconds, this works for me with MCUs that have internal resistor on USB data lines.

-- pa

ahansen
ahansenAuthor
Associate
August 1, 2018

Hi Pavel.

Thank you for the answer. Can you be specific about how you disable the USB controller?

Will USBD_DeInit() be sufficient?

Best Regards,

abaldur

Pavel A.
Pavel A.
Super User
August 1, 2018

Yes, USBD_Deinit should call the right USB driver function (thru several layers added by CubeMX )

Note that the correct behavior depends also on the host side. When the USB device disappears, the host application should immediately close its handle or whatever. Otherwise re-enumeration can fail or create duplicate zombie device.

-- pa

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