user20573: The problem occurred while testing a ping program with the ethercard examples from github.
Now no program will upload. It will say uploading.... and gets stuck there. The error message below appears:
Arduino: 1.6.7 (Windows 7), Board: "Arduino/Genuino Uno"

WARNING: Category '' in library UIPEthernet is not valid. Setting to 'Uncategorized'

Sketch uses 1,030 bytes (3%) of program storage space. Maximum is 32,256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xdf
Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

  This report would have more information with
  "Show verbose output during compilation"
  enabled in File > Preferences.


user15256: I'm having the same issue on my Macbook Pro. It happens randomly. The only solution i found is disconnecting the USB cable from the PC wait for a few mins and reconnect it again (possibly using another USB port).
It worked for me!

user33226: When you get this error, they have several things to check : 

Is my board reconised by Windows ? 
Is my board model is the right one ? 
Is the serial port is the right one ? 
Is my cable damaged ? 

Generally the upload problem is easy to fix. 
If your board is a custom one 

bootload problem 
crystal problem.  
reset not triggered properly ? (try to push it when arduino ide say "uploading sketch")


user34459: Disconnect everything to Arduino, Plug in your Arduino to your computer - check for the Serial port, Check for your Arduino Model, select programmer as USBasp, open up BLink sketch from Examples and HIT upload.
if you don't see your Arduino in Tools>Port then it should be the problem of USB cable, Computer USB port or "DRIVERS"

20573: <p>The problem occurred while testing a ping program with the ethercard examples from github.</p>

<p>Now no program will upload. It will say uploading.... and gets stuck there. The error message below appears:</p>

<pre><code>Arduino: 1.6.7 (Windows 7), Board: "Arduino/Genuino Uno"

WARNING: Category '' in library UIPEthernet is not valid. Setting to 'Uncategorized'

Sketch uses 1,030 bytes (3%) of program storage space. Maximum is 32,256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xdf
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xdf
Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

  This report would have more information with
  "Show verbose output during compilation"
  enabled in File &gt; Preferences.
</code></pre>
 15256: <p>I'm having the same issue on my Macbook Pro. It happens randomly. The only solution i found is disconnecting the USB cable from the PC wait for a few mins and reconnect it again (possibly using another USB port).
It worked for me!</p>
 33226: <p>When you get this error, they have several things to check : </p>

<ul>
<li>Is my board reconised by Windows ? </li>
<li>Is my board model is the right one ? </li>
<li>Is the serial port is the right one ? </li>
<li>Is my cable damaged ? </li>
</ul>

<p>Generally the upload problem is easy to fix. </p>

<p>If your board is a custom one </p>

<ul>
<li>bootload problem </li>
<li>crystal problem.  </li>
<li>reset not triggered properly ? (try to push it when arduino ide say "uploading sketch")</li>
</ul>
 34459: <p>Disconnect everything to Arduino, Plug in your Arduino to your computer - check for the Serial port, Check for your Arduino Model, select programmer as USBasp, open up BLink sketch from Examples and HIT upload.</p>

<p>if you don't see your Arduino in Tools>Port then it should be the problem of USB cable, Computer USB port or "DRIVERS"</p>
