I use the same code, with small changes, as ATMEL uses in its example - HID keyboard. I read most of the links you wrote. But no idea. The host does not send me a setup packet (GET_DESCRIPTOR). I monitor the communication on USB (applic. SourceUSB) and there are still GET_PORT_STATUS, CLEAR_PORT_FEATURE and SET_PORT_FEATURE then OS shows the error message - the USB device is not recognised. I programme the MCU via USB so in my opinion, the pin connection is OK. I think the device is still in Powered state and cannot move to Default state. Do I have to reset the device manually in the firmware to move to Default state or the MCU hardware does it itself? Should I answer the host anything before receiving the GET_DESCRIPTOR?