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STM32F107 Virtual Com example - echo needed

Question asked by otachkin.alexey on Dec 27, 2012
I have a problem with usage of ST-example for Virtual Com port. I have STM32F107 on my board. Example is downloaded correctly and all seems workable. The thing is that my board is not standard evaluation board and it doesn't use USART. So, I decided to change example code to make it work without USART - only with USB.
I'd lile to make Echo-program: device should return back all bytes, received from PC.
In the code I see sevearl places, where data is sended or received from USB:
1. EP1_IN_Callback (void)
2. EP3_OUT_Callback(void)
3. Handle_USBAsynchXfer (void)

Two moments need clarification:
1. in EP3_OUT_Callback(void) i retranslate data, received from USB on EP3 to USB on EP1 instead of USART. Is it correct way?
  USB_Rx_Cnt = USB_SIL_Read(EP3_OUT, USB_Rx_Buffer);
  USB_SIL_Write(EP1_IN, USB_Rx_Buffer, USB_Rx_Cnt);


2. The problem I encounter here, is that program crashes any time after usage of USB_SIL_Write, cycling in the HardFault_Handler function. What can be reason of it?

It would be great if anyone gives me any advices concerning this points.
Thanks in advance!