52840 USB CDC missed first byte in RX event

Hi,

I used 52840DK and SDK15.2 to test usb cdc, every thing goes will, but in rx event, it always missed first byte, for example, if send "123456", it just received "23456", if send just "1", there is no rx event. though I can see the first byte right in the internal_rx_buf, but how to make the rx event correctly receive first byte?

thanks!

Brian. 

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