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is there a reason using 2 separate usb endpoint for virtual com port example?

Question asked by shan on Oct 5, 2013
Latest reply on Oct 7, 2013 by shan
I was checking out the usb virtual com port loopback example provided in STM32_USB-FS-Device_Lib_V4.0.0.  

When I looked into the usb endpoint (usb_endp.c or usb_conf.h), it defines EP3 (OUT) and EP1(IN) as the endpoints for bulk data in and data out.  I wonder if there's any reason using two endpoints instead of one?   According to RM0038, there are 8 bi-direction endpoints or 16 single-direction endpoints for stm32l-discovery.  Can't we combine the two single-direction endpoint of EP3 and EP1 into one bi-direction endpoint, just like the EP0 bi-directional endpoint?  Is there any limitation doing this?  

Thanks a lot!