Blink

The aim of this practice is to switch ON and OFF two LEDs with our Raspberry Pi using Python3.

Materials:
-1 Raspberry Pi
-2 LEDs
-2 Resistors (1kΩ)
-Wires

To do that, first, we have to connect a LED and a resistor to the pins 17 and 27 of the Raspberry Pi. The end of the circuit will be in a pin of GND, also in our Raspberry Pi. We can mount it in a protoboard.

In the Raspberry Pi, we will open Python3 and we will write this code:


import RPi.GPIO as GPIO                                    //Here, we import the library GPIO to be able to use                                                                                  the ports GPIO of the Raspberry Pi.

import time                                                            //Here, we import the library time, to be able to use                                                                                    timing in the Raspberry Pi

GPIO.setmode(GPIO.BCM)                                 //Here, we say to the raspberry that we will use                                                                                         BCM to call the input and output ports
GPIO.setup(17,GPIO.OUT)                                 //Here, we stablish the port 17 as an output
GPIO.setup(27,GPIO.OUT)                                 //Here, we stablish the port 27 as an output

def blink():                                                            //In this part of the program, we will define the                                                                                           function blink, due to that we will do this program                                                                                   doing a call to a function
    print ('Ejecucion iniciada...')                            //We say on the screen that the program has started
    iteracion=0                                                       //We initializate the variable iteration as 0
    while iteracion<30:                                          //We start a while loop, that will finish when the                                                                                         variable iteracion be over 30
        GPIO.output(17,True)                                 //We will say here that the output of the pin 17 is                                                                                        TRUE
        GPIO.output(27,False)                                //We will say here that the output of the pin 27 is                                                                                        FALSE
        time.sleep(1)                                               //We will do a delay of 1 second
        GPIO.output(17,False)                               //We will say here that the output of the pin 17 is                                                                                       FALSE
        GPIO.output(27,True)                                //We will say here that the output of the pin 27 is                                                                                       TRUE
        time.sleep(1)                                               //Here, we will do a delay of 1 second
        iteracion=iteracion+2                                 //We will increase the variable iteracion
    print('Ejecucion finalizada')                           //Once the program has finished, we will say it on the                                                                                 screen
    GPIO.cleanup()                                              //Then, we will close the ports to avoid problems

blink()                                                                //This is the program, where we only call the function                                                                                called blink

And this is all the practice, it's very simple. If you want, you can download the program from here:
https://drive.google.com/folderview?id=0B20kHfrc3NnpTkszRUNvMF9nX1E&usp=sharing