Troubleshooting Guide For Arduino

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General troubleshooting advice

Make sure it’s actually an upload problem

The Arduino IDE compiles your code before uploading, so a bug in your code will also cause the upload to fail. But that is not an upload error. If you do a Sketch > Verify/Compile and still get a failure then you need to fix the compilation error before you have any hope of uploading. See the “Compiling” section of this guide for help with compilation errors.

Check the verbose output

The first thing to do when you have an upload problem is to turn on verbose output:

  1. File > Preferences
  2. Check the box next to “Show verbose output during: upload”.
  3. Click the “OK” button.

Now try uploading again. This time you will see useful information about the upload displayed in the black console window at the bottom of the Arduino IDE/Arduino Web Editor window. Note that the text will likely be longer than can be seen at once in the console window so you need to use the scrollbar on the right side to view it all.

Make sure you have the right board selected in the Tools > Board menu

Selecting the wrong board can result in an upload failure. After selecting the correct board from the Tools > Board menu, additional custom menus may appear under the Tools menu (e.g. Tools > Processor). Make sure you have the correct selections in those menus as well.

Specific issues

How do I know which port is my Arduino board?

Sometimes the port will be labeled with the board name in the Tools > Port menu. Other times it will not. If you don’t know which port is your Arduino, you can find it like this:

Arduino IDE:

  1. Unplug your Arduino board from the computer.
  2. Tools > Port
  3. Note the ports, if any, listed in the menu.
  4. Close the Tools menu. The ports list is only updated when the Tools menu is re-opened, so this step is essential.
  5. Plug your Arduino board into the computer.
  6. Tools > Port - The new port listed in the menu is your Arduino board.

Arduino Web Editor:

  1. Unplug your Arduino board from the computer.
  2. Click the board menu at the top of the Arduino Web Editor window.
  3. Click “Other Board & Port”.
  4. Note the ports, if any, listed in the menu.
  5. Close the “Other Board & Port” window.
  6. Plug your Arduino board into the computer.
  7. Click the board menu at the top of the Arduino Web Editor window.
  8. Click “Other Board & Port”. The new port listed in the menu is your Arduino board.

The Tools > Port menu is grayed out, or the port of my Arduino board doesn’t appear in the Tools > Port menu, or Arduino Web Editor doesn’t recognize my board

Make sure your USB cable is fully inserted into the socket on the Arduino board and the computer.

Some Arduino boards come with their pins inserted into anti-static foam. This foam is conductive, so you need to remove it before using the board.

You may need to install the driver for the USB to TTL serial adapter chip on your Arduino. Common USB chips:

You may be using a charge-only or defective USB cable. Try a different cable or test your cable on another device to confirm that it works for data.

If using a MKR board, remove any connections to pins 11 and 12. Many of the MKR boards have a power management chip that is controlled over I2C. If the I2C pins (11 and 12) are used for other than I2C devices, the communication with the power management chip may be disrupted (often indicated by the “CHRG” light continuously flickering) and no port appears.

Remove all external wiring, shields, modules, etc. from your Arduino board to see if it is the cause of the problem.

If you have a native USB board (e.g., Leonardo, Micro, MKR, Nano 33 IoT, Nano 33 BLE), see “Native USB board doesn’t get a port, or is failing uploads”.

If your board uses the ATmega16U2 USB to TTL serial adapter chip (marked “MEGA16U2” on the top of the chip), and you are using Windows, check Device Manager. If a device called “ATmega16u2 DFU” appears when you plug your board into the computer, this means the Arduino firmware is missing from the ATmega16U2. You can replace it by following these instructions: https://www.arduino.cc/en/Hacking/DFUProgramming8U2

Native USB board doesn’t get a port, or is failing uploads

If you have an ATmega32U4-based board (e.g., Leonardo, Micro, Pro Micro), and are using the Arduino IDE, try this:

  1. File > New
  2. Sketch > Upload
  3. Watch the black console window at the bottom of the Arduino IDE window.
  4. Wait until you see something like this: 
    Sketch uses 444 bytes (1%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
  5. Press and release the reset button (or momentarily connect a wire between the GND and RST pins on the Pro Micro). If you are using a Yun, you need to press and release the “32U4 RST” button quickly twice. The upload should now proceed successfully.

If you have an ATmega32U4-based board (e.g., Leonardo, Micro, Pro Micro), and are using the Arduino Web Editor, try this:

  1. Click the “New Sketch” button.
  2. Make sure you can see the black console window at the bottom of the Arduino Web Editor window. If you can’t see it, drag the status bar up until you can.
  3. Press and release the reset button (or momentarily connect a wire between the GND and RST pins on the Pro Micro). If you are using a Yun, you need to press and release the reset button quickly twice.
  4. Wait for the Arduino Web Editor to show a notification that your board has been connected.
  5. Immediately press the right pointing arrow button (Upload).
  6. Watch the black console window at the bottom of the Arduino IDE/Arduino Web Editor window.
  7. Wait until you see something like this: 
    Sketch uses 444 bytes (1%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
  8. Press and release the reset button (or momentarily connect a wire between the GND and RST pins on the Pro Micro). If you are using a Yun, you need to press and release the reset button quickly twice. The upload should now proceed successfully.

If you have a SAMD-based board (e.g., MKR, Nano 33 IoT), or a Nano 33 BLE board, try this:

  1. Press and release the reset button twice quickly. You should now see the onboard LED pulsing.
  2. Select the port of your board from the Arduino IDE’s Tools > Port menu.
  3. File > New
  4. Sketch > Upload

If the problem returns after you upload your previous sketch again, this indicates something in the sketch is breaking or stopping the USB code that runs in the background. Possible causes:

I don’t know which Tools > Programmer menu selection to use

The Tools > Programmer menu selection is only used when you are doing Tools > Burn Bootloader or Sketch > Upload Using Programmer. When you are doing a standard upload, the Tools > Programmer menu selection is completely ignored, so it doesn’t matter what you have it set to.

avrdude: ser_open(): can't open device ...: The system cannot find the file specified. or Couldn't find a Board on the selected port or the selected serial port does not exist or your board is not connected or avrdude: usbhid_open(): No device found or avrdude: jtag3_open_common(): Did not find any device matching VID 0x03eb and PID list: 0x2145 or avrdude: jtagmkII_recv_frame(): timeout or avrdude: jtagmkII_getsync(): sign-on command: status -1

Select the port of your Arduino from the Tools > Port menu.

If you don’t know which is the port, see “How do I know which port is my Arduino board?”

If the Port menu is grayed out, or the port of your Arduino does not appear on the menu, see “The Tools > Port menu is grayed out, or the port of my Arduino board doesn’t appear in the Tools > Port menu, or Arduino Web Editor doesn’t recognize my board”.

Error uploading, check if the selected board is currently available

See “The Tools > Port menu is grayed out, or the port of my Arduino board doesn’t appear in the Tools > Port menu, or Arduino Web Editor doesn’t recognize my board”.

avrdude: ser_open(): can't open device ...: Permission denied

Follow the instructions at: https://www.arduino.cc/en/guide/linux#toc6

If the problem persists after that, try uninstalling modemmanager.

avrdude: butterfly_recv(): programmer is not responding or avrdude: error: programmer did not respond to command or No device found on … An error occurred while uploading the sketch

Make sure you have selected the port of your Arduino from the Tools > Port menu.

If you don’t know which port it is, see “How do I know which port is my Arduino board?”.

If the Tools > Port menu is grayed or the port of your Arduino does not appear on the menu, see “The Tools > Port menu is grayed out, or the port of my Arduino board doesn’t appear in the Tools > Port menu, or Arduino Web Editor doesn’t recognize my board”.

If the correct port is already selected, see “Native USB board doesn’t get a port, or is failing uploads”.

avrdude: stk500_recv(): programmer is not responding, avrdude: stk500_getsync() attempt ...: not in sync or avrdude: stk500v2_ReceiveMessage(): timeout, avrdude: stk500v2_getsync(): timeout communicating with programmer

If you have a Nano derivative board or old official Arduino Nano: Select Tools > Processor > ATmega328P (Old Bootloader).

If you have a new (>=2018) official Arduino Nano board: Make sure you have Arduino AVR Boards 1.6.21 or newer installed (via Tools > Board > Boards Manager) and select Tools > Processor > ATmega328P.

Make sure you have selected the port of your Arduino board from the Tools > Port menu.

If you don’t know which is the port, see “How do I know which port is my Arduino board?”.

If the port of your Arduino does not appear on the menu, see “The Tools > Port menu is grayed out, or the port of my Arduino board doesn’t appear in the Tools > Port menu, or Arduino Web Editor doesn’t recognize my board”.

Remove any connections to pins 0 and 1 on your Arduino board. These pins are used for communication with your computer, including uploads. Connecting anything to these pins can interfere with uploads.

Remove all external wiring, shields, modules, etc. from your Arduino board to see if it is the cause of the problem.

If your board has an ATmega16U2 USB to TTL serial adapter chip (marked “MEGA16U2” on top), do a loopback test:

  1. Disconnect power from the board.
  2. Remove all connections and shields from the board.
  3. Force the processor to remain in reset by connecting a jumper wire from the RESET to the GND pin.
  4. Connect a jumper from the RX pin (Arduino pin 0) to the TX pin (Arduino pin 1).
  5. Connect the board to your computer.
  6. Select the port of your board from the Tools > Port menu.
  7. Tools > Serial Monitor
  8. Type some text into the input field at the top of the Serial Monitor window.
  9. Press Enter. If the text you typed is shown in Serial Monitor’s output window, the loopback test passed. If the text was not shown, the loopback test failed.
  10. Close Serial Monitor.
  11. Disconnect the board from the computer.
  12. Remove the two jumper wires.

If the loopback test failed, the USB to TTL serial adapter is damaged and it’s unlikely to be worth repairing your board.

If the loopback test passed, or if you skipped the loopback test, try doing a Burn Bootloader (see “How do I burn the bootloader?”).

If you have problems while burning the bootloader, see the “Burn Bootloader” troubleshooting page.

There is a bug in the “Old Bootloader” Nano and Pro Mini’s bootloaders that causes an endless reset loop after a reset caused by the watchdog timer, which results in this error when uploading accompanied by the onboard LED blinking rapidly. The way to recover from this is to burn the bootloader (see “How do I burn the bootloader?”). You can avoid having this problem happen again by installing a bootloader that doesn’t have the bug. If you have an ATmega328P @ 16 MHz board, select Tools > Board > Arduino Uno before burning the bootloader and use the board as an Uno thereafter. If your board has a different configuration, use MiniCore, and use the board with that MiniCore board selection thereafter.

avrdude: ser_open(): can't open device ...: Access is denied. or Error touching serial port or openPort(); Exception type - Port busy. or Error opening serial port '...'. (Port busy)

Make sure the port isn’t open in any other program.

Sometimes the port gets stuck open. Restarting your computer will resolve that issue.

Cannot run program "___REMOVE___...

See “fork/exec … : no such file or directory or exec: … : file does not exist or Cannot run program “REMOVE…”

WARNING: invalid value for unused bits in fuse "fuse5" or avrdude: jtagmkII_initialize(): Cannot locate "flash" and "boot" memories in description

This warning is normal, expected, and doesn’t indicate any problem. Please ignore it.

My keyboard or mouse emulation sketch is out of control, so I can’t upload a new sketch

  1. Unplug your Arduino board from your computer.
  2. Open the sketch you want to upload.
  3. Select the appropriate board from the Tools > Board menu.
  4. Hold down the reset button on your Arduino board. If you have a Pro Micro, there is no reset button, so you’ll need to use a wire to connect the GND and RST pins.
  5. Plug your Arduino board’s USB cable into your computer.
  6. Sketch > Upload
  7. Watch the black console window at the bottom of the Arduino IDE window. When you see something like this: 
    Sketch uses 3462 bytes (12%) of program storage space. Maximum is 28672 bytes.
Global variables use 149 bytes (5%) of dynamic memory, leaving 2411 bytes for local variables. Maximum is 2560 bytes.

    release the reset button (or disconnect the wire between the RST and GND pins on the Pro Micro).

The upload should now complete successfully.

SAM-BA operation failed

If you are using a MKR Vidor 4000, update the bootloader following these instructions: https://forum.arduino.cc/index.php?topic=563513.msg3839894#msg3839894

I can only upload once, then I need to burn bootloader before I can do the next upload

In order to upload, the bootloader needs to be activated. This is done by resetting the microcontroller. However, the bootloader only runs for a short time before timing out and switching to running your sketch so the reset has to be timed just right during the upload. Normally, we have an auto-reset circuit set up that resets the microcontroller at just the right time during the upload. The auto reset circuit consists of the DTR or RTS on the USB to TTL serial adapter chip connected to the reset pin via a 0.1 uF capacitor. You can use either DTR or RTS, it doesn’t matter which. This converts the signal on the DTR or RTS pin into a reset pulse at the right moment of the upload.

If you don’t have an auto-reset circuit, you’ll need to manually reset your Arduino at just the right time during the upload:

  1. Sketch > Upload
  2. Watch the black console window at the bottom of the Arduino IDE window until you see something like this: 
    Sketch uses 444 bytes (1%) of program storage space. Maximum is 30720 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
  3. Press and release the reset button. The upload should now finish successfully.

The reason why the reset (automatic or manual) is not needed on the first upload after burning the bootloader is because the microcontroller’s flash memory is erased during the Burn Bootloader process, which causes the bootloader to run constantly until the first upload is done.