LED (Simple)   Hardware

Equipments
1. Raspberry Pi
2. LED
3. Resistor 220 Ω 
Control by Linux Kernel - sysfs with GPIO
1. Setup GPIO for sysfs 
echo 4 > /sys/class/gpio/export
2. Set GPIO4 for output
echo out > /sys/class/gpio/gpio4/direction
3. Set GPIO4 output 1 (0: LOW, 1: HIGH)
echo 1 > /sys/class/gpio/gpio4/value
4. Set GPIO4 output 0 (0: LOW, 1: HIGH)
echo 0 > /sys/class/gpio/gpio4/value
5. Cancel GPIO4 node
echo 4 > /sys/class/gpio/unexport
  Python Control GPIO
import RPi.GPIO as GPIO
import time

# blinking function
def blink(pin):
        GPIO.output(pin,GPIO.HIGH)
        time.sleep(1)
        GPIO.output(pin,GPIO.LOW)
        time.sleep(1)
        return

# to use Raspberry Pi board pin numbers
GPIO.setmode(GPIO.BOARD)

# set up GPIO output channel, we set GPIO4 (Pin 7) to OUTPUT
GPIO.setup(7, GPIO.OUT)

# blink GPIO4 (Pin 7) 50 times
for i in range(0,50):
        blink(7)

GPIO.cleanup()