I have an Arduino Uno and Mega, but when I connect them to a computer with the USB they came with, there is no green light near the reset button that illuminates.

On the Uno board the pin 13 continuously flashes with red light while on the Mega board the R17 and R18 both illuminate red light but no flashing.

How do I know if the boards work or are damaged?

  • 2
    Does your Operating System recognize the Serial Port when you connect them? Have you tried uploading a sketch? Is there a reason to suspect they do not work? Some boards (like your Uno maybe) have a “blink” sketch installed by the manufacturer, others do not.
    – StarCat
    Commented Jan 15, 2021 at 6:57
  • 1
    in device manager in my computer nothing changes when i connect the Arduino. Yes I tried uploading files and the "port option" is gray. no reason to suspect it's working.
    – Amare.m
    Commented Jan 15, 2021 at 7:02
  • 1
    If the LED 13 is blinking, that's generally a good sign. I'd check the connection and try a different cable. On Windows, you might need to install the Arduino IDE first, because that includes the serial port driver for some of the boards.
    – PMF
    Commented Jan 15, 2021 at 8:45
  • the blinking is like in every one and half seconds. the power and the led 13 lights are both red. on the device manager of my computer, communication port (com11) appear with warning sign. but in the Arduino IDE the port is still gray .
    – Amare.m
    Commented Jan 15, 2021 at 10:36
  • 1
    See also: arduino.stackexchange.com/questions/153/…
    – RowanP
    Commented Jan 19, 2021 at 13:22

1 Answer 1


Did you try to connect to the computer and upload a blank sketch or a blink sketch... If the program complies and uploads successfully it is alive. But you will have to check IO, ADC and other features separately.

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