Hi, I work on diploma thesis and my objective is to design PCB and a firmware for contactless identification reader (RFID) which connects to computer with USB. PCB is done but now I have a problem with programming the microcontroller. I use Atmel AT89C5131. I am a beginner so I have no practice. The MCU does not receive any interrupt on endpoint 0, so I am not able to receive setup packet. I do not know where the problem is. I follow the example (HID keyboard) from Atmel but nothing is doing. I configure the PLL clock first, enable USB in USBCON register and set FEN bit in USBADDR register. Then I am waiting for endpoint 0 interrupt bit in UEPINT. No interrupt source is detected. Please help me and excuse for my English. Thank you very much for any reply...