Arduino Uno R3: No flashes on boot, can't upload to the board

Hi there,

The subject says it all. I can't remember what I was doing but now I have to Arduino Unos that once plugged in, the LEDs don't flash and all I get is this:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00

I have done many, many Google searches for this problem and most results offer the same advice. I follow the steps exactly and nothing works.

I'm on a Mac Running El Capitan 10.11.3 and to be honest, this OS release has caused more headaches in my life than any other Mac update. I have dfu-programmer-0.7.2 installed, I use homebrew, libusb is installed and when I check the system profiler I get this:

  Product ID:  0x0001
  Vendor ID:   0x2341
  Version: 0.01
  Serial Number:   85431303636351417182
  Speed:   Up to 12 Mb/sec
  Manufacturer:    Arduino (
  Location ID: 0x14100000 / 20
  Current Available (mA):  1000
  Current Required (mA):   100
  Extra Operating Current (mA):    0

after flashing the atmega16u2. Trying to upload a sketch results in the previous code message.

This is my first post asking for help, I hope the formatting is appropriate and I'm sure I'm missing details that you guys need to help troubleshoot.

The fact that I did this to two boards, weeks apart, is a pretty good indicator that the problem exists between the chair and the keyboard.



At the top of the forum is one of the pinned posts, Loop Back Test. Do that loop back test to make sure the ATmega16U2 is Ok.

If the pin 13 LED does not flash when you press and release the reset button, you need to burn the bootloader on the ATmega328P using another Arduino as an ISP programmer, or using a programmer device.