Hi, I'm new to the arduino world. I've got the Arduino Uno connected to my laptop via the usb cable. I have a green power light and I also have a blinking "L" light above the TX & RX. What does the blinking "L" light indicate? I've not found this situation described yet.
This is an LED connected to Arduino pin 13. See this page.
LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off.
nander:
What does the blinking "L" light indicate? I've not found this situation described yet.
The last program uploaded to the Arduino blinks the LED.
Look at the "Blink" example in the IDE.
So this blinking "L" is to be expected or normal when beginning?
Normal.
Blink (or something similar) is generally programmed before a board is shipped.
1 Like
Your Uno's working fine 
The 'L' led is actually connected to Digital Pin 13. In other words, it's a built-in LED for pin 13 and it flashes because it has the default blink sketch uploaded to it.
Once u upload another sketch (apart from the blink), the 'L' led will not flash anymore.
Hi Guys,
I have my own sketch loaded in my UNO but the L led is constantly on. Pin 13 is not connected to anything so what is the light telling me? Any clarity will be appriciated because my device isn't working 100%.
Thanks in advance.
Vash
Vash:
I have my own sketch loaded in my UNO but the L led is constantly on.
Could depend on what the code is doing.
i love you guys , for this detailed explanation, its been more than 3 months , since i received the arduino uno, but i was noob and thought i needed breadboard , resistors / diodes for this thing to work.,
but today when i connected arduino again and googled for blinking L led,
now i have managed to edit the blinking sketch , and change the blinking ms and its working fine.,
now i have managed to edit the blinking sketch , and change the blinking ms and its working fine.,
Congratulations
That LED being on by default annoys the $hit out of me so the first thing I do in most sketches is turn it off
$hit out of me
a linguistic resource, perhaps? . . . . 
waihung:
@nanderYour Uno's working fine
The 'L' led is actually connected to Digital Pin 13. In other words, it's a built-in LED for pin 13 and it flashes because it has the default blink sketch uploaded to it.
Once u upload another sketch (apart from the blink), the 'L' led will not flash anymore.
hey thanks dude.That was the thing I wanted to know
Indeed, is it still normal if the "L" light blinking after uploading the code?
Currently I'm using Arduino 1.6.12 + Arduino Uno R3 on Windows 7 64-bit.
Here's the code ov7670-no-ram-arduino-uno/ov7670_no_ram_arduino_uno at master · eranws/ov7670-no-ram-arduino-uno · GitHub