The Implement of AVR USB Programmer without USB Controller

USB port, with its convenience、fast speed and other good features, is (deeply)favored by more and more people. Compared to the previous serial and parallel port programmers, USB interface programmer doesn't need external power supplies, and download quickly ,so it is widely used. But the price of USB port programmer is higher than other programmers for its controller chip. This design uses the AVR single chip, whose most instructions are single cycle, and high-speed transmission. connecting the USB bus by the IO port of single chip, achieving the function of low-speed peripherals normed by USB specification. Therefore lower the development costs without external USB controller chips connection.