Electro Think

Raspberry pi Projects

Python GPIO

in these lessons we learn how to use raspberry pi gpio throw python, so I will try to cover the basics of python GPIO library in raspberry board step by step.
the gpio output voltage is 3.3v and the same in input signal also the maximum output current 30ma so it can drive a led diode but it will be batter if you use a transistor to protect the pin , as well any 5v signal it will be damaged the board so be aware of that. Post

so as you see the gpio have UART port for serial communication , I2C port, SPI and the rest of these it's a input or output pin that depending how you want to program it.

lessons

lesson 1:

make the pins number 16,18,22 an output and toggle it with delay 3 seconds.

import time
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BOARD)
GPIO.setup(22,GPIO.OUT)
GPIO.setup(16,GPIO.OUT)
GPIO.setup(18,GPIO.OUT)

GPIO.output(22,GPIO.HIGH)
GPIO.output(18,GPIO.HIGH)
GPIO.output(16,GPIO.HIGH)
time.sleep(3)
GPIO.output(16,GPIO.LOW)
GPIO.output(18,GPIO.LOW)
GPIO.output(22,GPIO.LOW)
GPIO.cleanup()
print "DONE"

lesson 2:

make the gpio 16,18,22 an output but this time you can control its status either "on" or "off".

import RPi.GPIO as GPIO
import time
pin_1=16
pin_2=18
pin_3=22
GPIO.setmode(GPIO.BOARD)
GPIO.setup(pin_1,GPIO.OUT)
GPIO.setup(pin_2,GPIO.OUT)
GPIO.setup(pin_3,GPIO.OUT)
GPIO.output(pin_1,GPIO.LOW)
GPIO.output(pin_2,GPIO.LOW)
GPIO.output(pin_3,GPIO.LOW)
while 1:
    re=raw_input("Enter the pin you want ON :- ")
    if re == "1":
        GPIO.output(pin_1,GPIO.HIGH)
    if re == "2":
        GPIO.output(pin_2,GPIO.HIGH)
    if re == "3":
        GPIO.output(pin_3,GPIO.HIGH)
    if re== "off all":
	GPIO.output(pin_1,GPIO.LOW)
	GPIO.output(pin_2,GPIO.LOW)
	GPIO.output(pin_3,GPIO.LOW)
    if re == "out":
        GPIO.cleanup()
        break

lesson 3:

how can we check the status of the pin and do something if the reading high or low.

import RPi.GPIO as GPIO
import time
pin_1=16
pin_2=18
pin_3=22
GPIO.setmode(GPIO.BOARD)
GPIO.setup(pin_1,GPIO.OUT)
GPIO.setup(pin_2,GPIO.OUT)
GPIO.setup(pin_3,GPIO.OUT)
GPIO.output(pin_1,GPIO.LOW)
GPIO.output(pin_2,GPIO.LOW)
GPIO.output(pin_3,GPIO.LOW)
print ("Enter 1,2,3 for leds and out to exit")
while 1:
    re=raw_input("Enter the pin you want ON :- ")
    if re == "1":
        if GPIO.input(pin_1):
            GPIO.output(pin_1,GPIO.LOW)
        else:
           GPIO.output(pin_1,GPIO.HIGH)            
    if re == "2":
        if GPIO.input(pin_2):
            GPIO.output(pin_2,GPIO.LOW)
        else:
           GPIO.output(pin_2,GPIO.HIGH) 
    if re == "3":
        if GPIO.input(pin_3):
            GPIO.output(pin_3,GPIO.LOW)
        else:
           GPIO.output(pin_3,GPIO.HIGH) 
    if re == "out":
        GPIO.cleanup()
        break

lesson 4:

generate PWM signal from pin 22 to control for example speed of a motor or the angle of the servo motor and more.

import RPi.GPIO as GPIO
import time
pwm_pin=22
GPIO.setmode(GPIO.BOARD)
GPIO.setup(pwm_pin,GPIO.OUT)
pwm=GPIO.PWM(pwm_pin,50)
pwm.start(0)
print ("Enter number for pwm from 0-100")
print ("Enter out for exit")
while 1:
    p=raw_input("Enter the pwm value:- ")
    if p =="out":
        pwm.stop()
        GPIO.cleanup()
        print "DONE"
        break
    else:
        dc= float(p)
        pwm.ChangeDutyCycle(dc)

lesson 5:

activated the pull-up resistors and change the status of the pin every time pressing the switch that connects to pin 26.

#this is toggle program
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BOARD)
GPIO.setup(26,GPIO.IN,pull_up_down=GPIO.PUD_UP)
GPIO.setup(22,GPIO.OUT)
GPIO.output(22,GPIO.LOW)
try:
    while 1:
        if (GPIO.input(26)==0) and (GPIO.input(22)==1):
                GPIO.output(22,GPIO.LOW)
                GPIO.wait_for_edge(26,GPIO.RISING)
        if (GPIO.input(26)==0) and (GPIO.input(22)==0):
                GPIO.output(22,GPIO.HIGH)
                GPIO.wait_for_edge(26,GPIO.RISING)
except KeyboardInterrupt:
    GPIO.cleanup()
    print "DONE"

lesson 6:

this code will print a message when you press the button that connects to pin 26 and waiting in an empty loop until button released.

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BOARD)
GPIO.setup(26,GPIO.IN,pull_up_down=GPIO.PUD_UP)
coun=0
while 1:
        GPIO.wait_for_edge(26,GPIO.FALLING)
        print "key has been press"
        GPIO.wait_for_edge(26,GPIO.RISING)
        print "key has been released"
        coun+=1
        if coun==10:
            GPIO.cleanup()
            break