The USBtinyISP is a programmer for AVR controllers. Since you never have enough programming devices and this one is compatible with AVR studio, I built it.
The core of the device is the ATtiny 2313A. This controller is managing USB and ISP. The data then is buffered in a 74HC125 for clean signals and timing.
For the normal USB data voltage of 3.3V there are some z-diodes for protection.
Schematic and Layout aren’t that complicated, but I had to use some wire bridges. I wanted the programmer to be small, but still routed only on one side . But the original EAGLE-files are available on the Adafruit website if you want them.
For compatability I included two different ISP-headers. One 6pin and one 10pin. So you don’t have a problem with adapters.
And here the original schematic as well as pictures of my build