"And additionally you can connect Zener diodes (3.6V) to USB D+ and D- data lines"
Come lo o li metto i zener? D+ ---->|--- D- o D+ ---->|--- D+ D- ---->|--- D-
??
E' per questo circuito.
---------- FAQ: Q: After device plugin into USB port is the device not recognized - recognized only as "Unknown USB device". A1: Problem of bad device detection is in hardware. In schematic you must add series resistors into USB data lines - see schematic on my website. You can increase the resistors from 68R up to 330R. And additionally you can connect Zener diodes (3.6V) to USB D+ and D- data lines. Problem appears mainly on notebooks and new computers. Usually is there no problem when you plug device into external USB hub. Problem is caused by high voltage coming from microcontroller to USB lines - allowed max. 3.6V (input current into computer USB port). A2: If you are using ATtiny2313 you must set fuses during programming: disable division the external clock by 4 and enable high speed XTALL. Note: No driver update helps ;-) .