Why pin logic on NRF52-DK is interchanged?

Question

Hi,
I develop application on MBED platform with NRF52-DK. I figure out that pin "logic" on this board is interchanged. For example. I have LED connected to some pin. When I set this pin high (set 1) then LED light off and setting this pin low (zero) switch on the LED. Why? How to change such strange situation? Is it bug or standard (intentional) design for this MCU?

RK · Accepted Answer

Of course it's not a bug, nor does it have anything to do with the MCU nor the GPIO nor is it strange in any way at all nor is the logic on the pin 'interchanged'. Just look at the circuit diagram, the LEDs are connected to VDD via a resistor so pulling the GPIO low lights them. If you read the manual for the DK, which is only a few pages long it states 
 The LEDs are active low, meaning that writing a logical zero ('0') to the output pin will illuminate the LED.
 
 Nothing to be 'solved' here.

Why pin logic on NRF52-DK is interchanged?

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