My goal is to create the simplest possible V-USB based device. It won't to anything, just be visible to the system as a Libusb device. May not sound too interesting, but see it as a framework for further developement. Hardware Based on a ATTiny25. Two 1N4148 in the USB power line, 100n and 10-47u capacitors over plus and ground. 68 ohm resistors on D+ and D-, 1k5 pull-up on D-. Software First, the standard V-USB code is used. In usbconfig.h the following is changed: #define USB_CFG_MAX_BUS_POWER 100 #define USB_CFG_VENDOR_ID 0x16, 0xc0 #define USB_CFG_DEVICE_ID 0x05, 0xdf #define USB_CFG_VENDOR_NAME 'p', 'a', 't', 'r', 'i', 'k', 'h', 'e', 'r', 'm', 'a', 'n', 's', 's', 'o', 'n', '.','s','e' #define USB_CFG_VENDOR_NAME_LEN 20 #define USB_CFG_DEVICE_NAME 'u', 's', 'b', '-', 't', 'e', 's', 't' #define USB_CFG_DEVICE_NAME_LEN 8 I'm not yet convinced how to set the and USB_CFG_VENDOR_ID and USB_CFG_DEVICE_ID for my non-commercial project. I don't own a VID/PID . Fuse settings; spien enabled bod disabled Nothing else enabled. pll clock, startuptime pwrdwn/reset:1k ck/14 +4ms In hex-format: Ext 0xff high 0xDF low 0xc1