Situation: The Arduino sketch compiles without error but does not upload to the Arduino itself. An error message appears.

Common causes:

  1. The Arduino is not receiving power even after the USB cable is plugged in. Look for the power light on the top of the Arduino. If it is not on check the USB cable is completely plugged in at both ends. Also check any wiring added to the Arduino. Look specifically for electrical paths that connect Vin to GND or +5v to GND. If the latter is the situation not only will the Arduino not receive power but the voltage regulator on the Arduino may become hot. If left long enough the Arduino may be damaged.
  2. The Arduino device driver is not installed. On Windows open the device manager and look for a device that is not installed or not working. It will be labeled Arduino. Refer to the Arduino software installation instructions to install a driver.
  3. The com port associated with the Arduino is not available. Close all open instances of the Arduino, unplug the Arduino USB cable from the computer, wait about 10 seconds, plug the USB cable back in, wait a few seconds, then restart the Arduino IDE.
  4. Check the type of board. Some require a special procedure for uploading. The Adafruit Trinket Pro, for example, requires a button to be pushed prior to upload.
  5. Occasionaly we've found a defective or damaged Arduino that appears incapable of connecting to a computer. Try your Arduino on a different computer.