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Author Topic: Boards LED on pin 13 Flashes continously  (Read 699 times)
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When I plug my Arduino Uno into the usb port on my computer, the built in LED on the board flashes.  This is before I start my Arduino software.  It will continue after I press the reset button. 

When I run the very basic blink sketch, there are two other built in LEDs on the Uno that also flash, but then go out. 

I am running the Arduino software on a computer running Window XP Service pack 3.

Any suggestions?
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Left Coast, CA (USA)
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Sounds like normal operation to me? The bootloader on the controller chip uses/manages pin13 led until it passes control over to a uploaded sketch, then the sketch controls what you do with pin13 led.

Lefty
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Thanks Lefty.  I had a lot of problems just getting the computer I am using to load the software.  When I first got my Uno, I had a dedicated laptop for it.  I was scanning for viruses, malware, etc one day when the mother board burnt out.  The Uno software and hardware worked great on it.  Right now I have my Uno plugged into my new laptop running windows 8, and the led on pin 13 is flashing.  Thank you for clarifying this
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This is before I start my Arduino software.
The Arduino board will run whatever program it has regardless of what you are doing on your PC.

  It will continue after I press the reset button. 
That starts the previously loaded program over, not erases the memory.


there are two other built in LEDs on the Uno that also flash, but then go out. 
I'm going to guess they say "TX" and "RX" next to them... probably a hint to why they flash.
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James C. 
  Yes you were right about the tx and rx leds.  Any idea about what would happen if I burned my bootloader?  I saw that when I was on my tools menu.
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Any idea about what would happen if I burned my bootloader?

If you have a hardware programmer attached (which is listed in the Programmer part of the menu), then the bootloader will be re-programmed.  Otherwise, nothing will happen.
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Just a small addition, When I'm prototyping a design, I always upload a blank sketch (Bare minimum) to the UNO/Leo/MEGA , when I finish working for the day - That way when I turn it on, regardless of what I decide to hook up to it, the IO pins will be HiZ (High Impedance).
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Thanks spycatcher2k.  I modified a the blink program to set pin 13 low and go into a loop.  now it stays out.  I will do what you do.  Thanks for the tip
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