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Using Arduino => Installation & Troubleshooting => Topic started by: spierepf on Mar 30, 2012, 08:06 am

Title: Should the onboard pin 13 LED be lit by default?
Post by: spierepf on Mar 30, 2012, 08:06 am
Greetings,

When I load a do-nothing sketch onto my Arduino UNO R3, the pin 13 LED lights up. My understanding is that by default all pins are supposed to be in a high-impedance state. Have I burnt out that pin?

Peter.
Title: Re: Should the onboard pin 13 LED be lit by default?
Post by: nickgammon on Mar 30, 2012, 08:17 am
I think we had this one recently. But the search feature isn't that good.

I think pin 13 may be HIGH but INPUT. The effect is that it will appear lit up. In other words, it is  high-impedance but with a weak pull-up. An artifact of how the bootloader leaves it.
Title: Re: Should the onboard pin 13 LED be lit by default?
Post by: smeezekitty on Mar 31, 2012, 06:14 am
The pull up may be enabled for some reason.
Try explicitly setting the pin low.