ATxmega programmer has different interface than 8-bit AVRs. It uses PDI interface instead of ISP. If you don’t want to buy new programmer for ATxmega you can try this little hack done by Szu. He uses USBASP (USB in-circuit programmer for Atmel 8-bit AVR controllers) with some modification to program AVR ATxmega. The hack convert SCK line to PDI DATA and MOSI becomes PDI CLK. Be sure to drop SCK and MOSI voltage from 5V to 3.3V using zener and resistor since PDI operates at 3,3V.
Next step is upgrading your USBASP Firmware with new firmware that supporting PDI.
For more detail: Programming AVR ATxMega using USBasp and ATxmega microcontroller
This free embedded project also found using:
- usbasp pdi
- usbasp xmega
- rotary encoder atmega32
- programming usb atxmega