Can't upload to my Nano after updating to Arduino AVR Boards 1.6.21 I recently had the Arduino IDE notify me of available boards updates, so I updated. Since then when I try to upload to my Nanos it fails:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x01

avrdude done.  Thank you.

Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.


I installed Arduino IDE 1.0.6 and found that I can upload to all my Nanos with that IDE version.

How can I upload to my Nanos using Arduino AVR Boards 1.6.21?
Arduino recently changed the bootloader they ship on their official Nano boards. This required a change in the hardware definition for the Nano, which was the sole reason for the Arduino AVR Boards 1.6.21 release.

The new Nano hardware definition is not backwards compatible with Nanos that use the previous ATmegaBOOT bootloader. For this reason a new menu option was added: Tools > Processor > ATmega328P (Old Bootloader). If you select that option the uploads to your Nanos will work again.