I noticed there are two Gnd pins at the lower pin strip, and another on the upper strip. Is there a difference in their purpose?

1 Answer 1


In short, all the UNO ground pins are the same.

They are just there to make your life easier. At the end of the day, GND is GND. There is no technichal difference. Just note that is is sometimes better if you share the 3 GND ports. Overloading a port might damage it. Check the datasheet for current limitations of the pins.


The pins (literal pins of the IC) themselves are also different on the ATmega IC.

  • Your last statement is confusing. The ATmega has several ground pins, but they are all connected together on the PCB, just like all the GND header pins are connected together. At the end, all grounds are a single electrical node. Also, I doubt you can overload a GND header pin : you will very likely burn the regulator or the USB fuse before. Commented Oct 21, 2016 at 15:34
  • @EdgarBonet, well I prefer to specify it!
    – Dat Ha
    Commented Oct 21, 2016 at 16:14
  • 1
    You linked to the wrong datasheet. The question is about the GND pins of the headers on the board, not about the pins of the microcontroller. This makes your answer misleading, as a naive reader may assume that the current sinked by the GND header pins goes into the GND MCU pins. Commented Oct 21, 2016 at 17:05
  • So, @EdgarBonet, considering I was indeed referring to the headers on the board, what's the truth here?
    – Dor
    Commented Oct 26, 2016 at 10:39
  • @Dor: As already stated, all the GND pins are connected together, so they are equivalent. My previous comment is just pointing out that the linked datasheet is irrelevant to your question. Commented Oct 26, 2016 at 10:53

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