user13972: Whenever I try to program my Arduino UNO Rev.3, I'm seeing the following error
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00

When I plug this in, I do see a power light. There are no cables whatsoever connected other than the USB. I have another Arduino UNO which works fine when I upload the sketch (I'm using the basic blink sketch). How do I resolve this? What kind of problem can it be?

user39459: Have you already tried this?
https://stackoverflow.com/a/20735393/5507619

I had this problem with a Crowduino, running the Arduino IDE on OSX.
  The solution for me was to switch on verbose output during upload (in
  the arduino IDE preferences pane).
Then, when uploading, you can see avrdude sending three packets
  avrdude: Send: 0 [30]   [20] (with corresponding RX flashes on the
  board) right before the avrdude: ser_recv(): programmer is not
  responding error.
The trick is to hit the reset button on the board immediately before
  these three packets are sent. Then the program will be uploaded
  successfully.


user37164: I had periodically encountered this as well and was stumped after I had tried all the recommended solutions I could find. In my particular case it turned out to be the cable I was using.

user46088: I was having the same problem, however I was able to solve as follows,

rebooting my computer
or, changing the cable, basically switching between 2 USB cables (may be it just needed to unplug the USB and plug it in again).
or, resetting the COM port

closing the Arduino IDE
disabling the COM port
enabling the COM port
opening the Arduino IDE



user53411: I had this problem when working with Arduino IDE and XOD running on top of it.
What I found; looked like baud rates were being set differently at different stages in the setup. I compared Windows 'device settings', arduino IDE settings and XOD settings...and they are not the same and seem to change ? ...hence the 'avrdude:stk500_**** errors!
To demonstrate
Connect an Arduino board to a PC USB socket.

On Windows 7; Control Panel\ System and Security\System\ Device Manager... then double-click on 'Ports (COM & LPT)
You should see FTDI
or
USB-SERIAL CH340(COM7) ... for a chinese serial com chip on the arduino board.
Right-click on this and check 'Properties\ Port Settings' and note  the 'Bits per second' value : e.g. 57600 ... (write it down !)
Open the arduino IDE and click on File\Preferences and tick the option ;'Show verbose output during: 'upload'.Then close the 'Preferences' screen.
Load a small program that works. e.g. File\Examples\01.Blink
In the for your arduino board setup in the Arduino IDE;
Tools\Board ... such as Arduino Nano
Tools\Processor ... such as ATmega328P
Tools\Port:COM7 for example ... make sure a tick is selected.
Tools\Get Board Info ... will show info from the arduino serial chip (a good sign your usb cable works!)
On the IDE toolbar select;

'Verify' and shortly it should show 'Done Compiling'
Click 'Upload' and the Blink program should load into the arduino chip. 

Now here is the interesting observation; The 'verbose message at the bottom of the IDE screen will indicate what 'Overriding Baud Rate : XXXXX' is being used! Write this number down next to the value you found on the Windows devices setting.
Now, if you are a XOD man, leave the arduino IDE running and run XOD.
Open the XOD IDE and open (Deploy) say the 01-hello program and load it into your arduino board.
Select'welcome-xod' and select 01-hello program on left-side menu.
Select 'Deploy\Upload to Arduino ...'
select 'Board model:'  and 'Serial port:' ... eg COM7
Scroll up in the 'Deployment ' window and there will be another value labeled 'Overriding Baud Rate : e.g.115200'

I HAVE FOUND THESE BAUD RATE SETTINGS CHANGE INEXPLICABLY !
I hope my observations will throw some light on your problem of erratic uploads.

user46116: After trying numerous suggestions, 2 different boards, 3 different cables on a WinXP and a Win7 machine, I finally got things working by going to "Tools -> Processors -> ATmega 328P Old Bootloader" 

13972: <p>Whenever I try to program my Arduino UNO Rev.3, I'm seeing the following error</p>

<pre><code>avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00
</code></pre>

<p>When I plug this in, I do see a power light. There are no cables whatsoever connected other than the USB. I have another Arduino UNO which works fine when I upload the sketch (I'm using the basic blink sketch). How do I resolve this? What kind of problem can it be?</p>
 39459: <p>Have you already tried this?
<a href="https://stackoverflow.com/a/20735393/5507619">https://stackoverflow.com/a/20735393/5507619</a></p>

<blockquote>
  <p>I had this problem with a Crowduino, running the Arduino IDE on OSX.
  The solution for me was to switch on verbose output during upload (in
  the arduino IDE preferences pane).</p>
  
  <p>Then, when uploading, you can see avrdude sending three packets
  avrdude: Send: 0 [30]   [20] (with corresponding RX flashes on the
  board) right before the avrdude: ser_recv(): programmer is not
  responding error.</p>
  
  <p>The trick is to hit the reset button on the board immediately before
  these three packets are sent. Then the program will be uploaded
  successfully.</p>
</blockquote>
 37164: <p>I had periodically encountered this as well and was stumped after I had tried all the recommended solutions I could find. In my particular case it turned out to be the cable I was using.</p>
 46088: <p>I was having the same problem, however I was able to solve as follows,</p>

<ul>
<li>rebooting my computer</li>
<li><p>or, changing the cable, basically switching between 2 USB cables (may be it just needed to unplug the USB and plug it in again).</p></li>
<li><p>or, resetting the COM port</p>

<ol>
<li>closing the Arduino IDE</li>
<li>disabling the COM port</li>
<li>enabling the COM port</li>
<li>opening the Arduino IDE</li>
</ol></li>
</ul>
 53411: <p>I had this problem when working with Arduino IDE and XOD running on top of it.
What I found; looked like <strong>baud rates were being set differently at different stages in the setup</strong>. I compared Windows 'device settings', arduino IDE settings and XOD settings...and they are not the same and seem to change ? ...hence the 'avrdude:stk500_**** errors!</p>

<p><strong>To demonstrate</strong></p>

<p>Connect an Arduino board to a PC USB socket.</p>

<ol>
<li><p>On Windows 7; Control Panel\ System and Security\System\ Device Manager... then double-click on 'Ports (COM &amp; LPT)</p>

<p>You should see FTDI</p>

<p>or</p>

<p>USB-SERIAL CH340(COM7) ... for a chinese serial com chip on the arduino board.
Right-click on this and check 'Properties\ Port Settings' and note  the 'Bits per second' value : e.g. 57600 ... (write it down !)</p></li>
<li><p>Open the arduino IDE and click on File\Preferences and tick the option ;'<strong>Show verbose output during: 'upload</strong>'.Then close the 'Preferences' screen.</p></li>
<li><p>Load a small program that works. e.g. File\Examples\01.Blink</p></li>
<li><p>In the for your arduino board setup in the Arduino IDE;</p>

<p>Tools\Board ... such as <em>Arduino Nano</em></p>

<p>Tools\Processor ... such as <em>ATmega328P</em></p>

<p>Tools\Port:COM7 for example ... make sure a tick is selected.</p>

<p>Tools\Get Board Info ... will show info from the arduino serial chip (<strong>a good sign your usb cable works!</strong>)</p></li>
<li><p>On the IDE toolbar select;</p>

<ul>
<li><p>'Verify' and shortly it should show 'Done Compiling'</p></li>
<li><p>Click 'Upload' and the <em>Blink</em> program should load into the arduino chip. </p></li>
</ul></li>
<li><p>Now here is the interesting observation; The 'verbose message at the bottom of the IDE screen will indicate what '<strong>Overriding Baud Rate : XXXXX'</strong> is being used! Write this number down next to the value you found on the Windows devices setting.</p></li>
<li><p>Now, if you are a XOD man, leave the arduino IDE running and run XOD.</p></li>
<li><p>Open the XOD IDE and open (Deploy) say the <em>01-hello</em> program and load it into your arduino board.</p></li>
<li><p>Select'welcome-xod' and select 01-hello program on left-side menu.</p></li>
<li><p>Select 'Deploy\Upload to Arduino ...'</p></li>
<li><p>select 'Board model:'  and 'Serial port:' ... eg COM7</p></li>
<li><p>Scroll up in the 'Deployment ' window and there will be another value labeled <strong>'Overriding Baud Rate : e.g.115200'</strong></p></li>
</ol>

<p>I HAVE FOUND THESE BAUD RATE SETTINGS CHANGE INEXPLICABLY !</p>

<p>I hope my observations will throw some light on your problem of erratic uploads.</p>
 46116: <p>After trying numerous suggestions, 2 different boards, 3 different cables on a WinXP and a Win7 machine, I finally got things working by going to "Tools -> Processors -> ATmega 328P Old Bootloader" </p>
