I have written C8051F340USB to serial program, 115200 baud following test basic stability, made ​ ​ up sharing under.

UART1
.....\cyglink.txt
.....\define.h
.....\description.#1
.....\description.#2
.....\description.h
.....\F340-USB
.....\F340-USB.M51
.....\F340-USB.uvgui.Administrator
.....\F340-USB.uvopt
.....\F340-USB.uvproj
.....\F340_Init.c
.....\F340_Init.h
.....\F340_Init.LST
.....\F340_Init.OBJ
.....\F340—USB
.....\F340—USB.#1
.....\F340—USB.#2
.....\F340—USB.#3
.....\F340—USB.hex
.....\F340—USB.M51
.....\F340—USB.wsp
.....\F34x_USB_Config.h
.....\F34x_USB_Registers.h
.....\F34x_USB_Structs.h
.....\includes.h
.....\keilkilll.bat
.....\main.c
.....\main.LST
.....\main.OBJ
.....\MyType.h
.....\SiBulk.sys
.....\SilabsBulk.inf
.....\STARTUP.A51
.....\STARTUP.LST
.....\STARTUP.OBJ
.....\tmp.out
.....\UART.C
.....\UART.h
.....\UART.LST
.....\UART.OBJ
.....\USB.c
.....\USB.h
.....\USB.LST
.....\USB.OBJ
.....\UsbToUartDriver.inf
.....\USB_Service.#1
.....\USB_Service.#2
.....\USB_Service.c
.....\USB_Service.LST
.....\USB_Service.OBJ

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