stm32usb library bug and solution-EEWORLD

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When I was developing the stm32usb device for my project, I found that the usb sending would often block the main function, or the program could not run smoothly, and the real-time performance was greatly reduced. It was normal for it to be stuck for tens of milliseconds. I don't understand why st would write such a usb program. It's really stupid. After several twists and turns, I found a solution:

In the usb_dcusb_dcd_int.c file, the function DCD_WriteEmptyTxFifo has a bug, which will often cause an infinite loop and make the USB library take too long.
It should be modified as follows, adding the statement in the red box to the original program:

The USB connection is not a reliable real-time connection, and it is normal to lose packets sometimes. After the modification, the USB will no longer be blocked and will be very smooth, but you should pay attention to adding packet loss processing logic to solve the USB packet loss problem. I am using a USBHID device, and the source code of the upper computer three platforms is attached https://download.csdn.net/download/u012572552/10612090

Keywords：stm32 bug Reference address：stm32usb library bug and solution

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