user4856: I had problems with Arduino uno and reseted firmware. Followed this tutorial. Now I can't upload my code Arduino IDE says:
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

I tried loop-back mode, everything is fine.
Firmware was located in this location:
/usr/share/arduino/hardware/arduino/firmwares/atmegaxxu2/Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex


user10794: There are two processors on the Uno board.

The Atmega328P which is the "main" processor with your sketches on it
The Atmega16U2 which handles the USB interface


Firmware was located in /usr/share/arduino/hardware/arduino/firmwares/atmegaxxu2/Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex

Hopefully you reflashed the Atmega16U2 with that file. Did you?

I tried loop-back mode, everything is fine.

Therefore the Atmega16U2 is OK. The problem may be with the Atmega328P.


I had problems with Arduino Uno and reseted firmware.

You shouldn't need to do this, I never reflash the firmware on my Atmega16U2. 
What problems did you have? Did it involve motors? LEDs? High voltages? Sparks? Flames? Screaming?
Please see the steps described here, run through them, and see if that fixes the problem: Have I bricked my Arduino Uno? Problems with uploading to board

4856: <p>I had problems with Arduino uno and reseted firmware. Followed this <a href="http://bartruffle.blogspot.fr/2013/09/dfu-programming-atmega16u2-on-arduino.html" rel="nofollow">tutorial</a>. Now I can't upload my code Arduino IDE says:</p>

<pre><code>avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00
</code></pre>

<p>I tried loop-back mode, everything is fine.</p>

<p>Firmware was located in this location:</p>

<pre><code>/usr/share/arduino/hardware/arduino/firmwares/atmegaxxu2/Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex
</code></pre>
 10794: <p>There are two processors on the Uno board.</p>

<ul>
<li>The Atmega328P which is the "main" processor with your sketches on it</li>
<li>The Atmega16U2 which handles the USB interface</li>
</ul>

<blockquote>
  <p>Firmware was located in /usr/share/arduino/hardware/arduino/firmwares/atmegaxxu2/Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex</p>
</blockquote>

<p>Hopefully you reflashed the <strong>Atmega16U2</strong> with that file. Did you?</p>

<blockquote>
  <p>I tried loop-back mode, everything is fine.</p>
</blockquote>

<p>Therefore the Atmega16U2 is OK. The problem may be with the Atmega328P.</p>

<hr>

<blockquote>
  <p>I had problems with Arduino Uno and reseted firmware.</p>
</blockquote>

<p>You shouldn't need to do this, I never reflash the firmware on my Atmega16U2. </p>

<p>What problems did you have? Did it involve motors? LEDs? High voltages? Sparks? Flames? Screaming?</p>

<p>Please see the steps described here, run through them, and see if that fixes the problem: <a href="https://arduino.stackexchange.com/questions/13292/have-i-bricked-my-arduino-uno-problems-with-uploading-to-board">Have I bricked my Arduino Uno? Problems with uploading to board</a></p>
