$ pwd /Applications/Arduino.app/Contents/Resources/Java/hardware/arduino/firmwares/atmegaxxu2 $ avrdude -p atmega16u2 -F -P usb -c avrispmkii -U flash:w:Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex -U lfuse:w:0xFF:m -U hfuse:w:0xD9:m -U efuse:w:0xF4:m -U lock:w:0x0F:m avrdude: stk500v2_command(): command failed avrdude: stk500v2_program_enable(): bad AVRISPmkII connection status: MOSI fail, SCK fail avrdude: initialization failed, rc=-1 avrdude: AVR device initialized and ready to accept instructions avrdude: Device signature = 0x000000 (retrying) avrdude: Device signature = 0x000000 (retrying) avrdude: Device signature = 0x000000 avrdude: Yikes! Invalid device signature. avrdude: Expected signature for ATmega16U2 is 1E 94 89 avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed To disable this feature, specify the -D option. avrdude done. Thank you.
配線が悪そうなのでテスターで調べると、16u2のICSPのMOSIとMISO（１番と２番）がショートしていた
このエラーがでるときは高電圧で死んでいるらしい
http://cloudcapt.hatenablog.com/entry/2015/05/05/193652
16u2は交換できないのでこれ以上どうしようもない
AVR ISP mkIIを使ってATmega328p専用機（USBシリアル通信出来ないので非常に使い途が無い）
にするしかなさそう
