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STM32F103 USB Virtual COM Port usb unplug lock issue

Question asked by jkwool on Mar 8, 2014
Latest reply on Apr 15, 2014 by Amel N
Hi, I have a fairly standard implementation of the Virtual COM Port for the STM32F103. All i have implemented currently is the VCP code and an LED flashing in the main loop.

The board can be powered by either USB or External Power supply.

Everything works fine when powered by USB, i.e. VCP works and LED flashes in main routine. When i pull the USB cable while also powering the board by the external power supply the STM32 seems to lock up and the LED stops flashing (stays solid). As soon as i plug the USB back in the LED begins flashing again?!?!

Has anyone come across anything like this before? I really need the STM32 to continue to function as normal when powered by the external power supply with the USB either plugged in or not plugged in.