As we mentioned earlier, we are using LPC4357 and planning to use one USB controller as mass storage host and another one as HID device. We downloaded the code from NXPUSBLIB and done bear minimum testing for the HOST. Now complied the code as both Device and Host macro on. In the device mode, there is a function called - CALLBACK_USB_GetDescriptor which is used in USB_Device_SetConfiguration and USB_Device_GetDescriptor (in DeviceStandardReq.c file) However there is no source code for the function call -- CALLBACK_USB_GetDescriptor. Eventually we would like to use USB ROM device driver, however, wanted to conduct initial testing . You did mention that you are not supporting this library anymore. However, if you have a source code (or link to source code) for - CALLBACK_USB_GetDescriptor function please let us know.