Experiment Zero. Lighting a Light Emitting Diode. A \(330 \Omega\) resistor is connected in series to the diode in order to limit the current that flows from the RPi through the LED. One terminal of the series is connected to a ground (GND) pin of the GPIO, the other terminal of the series is connected to the GPIO pin 17, a pin selectable for digital output. The LED has to be correctly polarized, connecting the shorter leg (the cathode) to the lower potential. An individual GPIO pin can only safely provide \(16 mA\) \cite{documentationa,documentationg}. If we use a maximum voltage of \(+3.3 V\), according to Ohm's law the minimum resistance connected between the high voltage pin and the ground pin should be \(R_{\min} = 3.3 V / 16 mA \simeq\ 206 \Omega\). Moreover, the GPIO pins can provide all together a maximum current of \(50 mA\), distributed on all the pins.