This is a part of the slide set used at the MakerSpace Noida (India) launch event, Pi Maker Workshop. This slide set is designed to help people get started with the Raspberry Pi and also serves as a collection of innovative projects and some core basic concepts that can aid anybody with their first few steps into the world of DIY electronics or maybe serve as a refresher for the experienced. Feel free to refer and share but please don't alter the watermarks :)

1. Pi Maker
Workshop
Powered by:
http://www.inventrom.com/http://www.robotechlabs.com/
Mayank Joneja
botmayank.wordpress.com
botmayank@gmail.com
4.GPIO Access

2. Mayank Joneja
Warning!
 While the GPIO pins can provide lots of useful control
and sensing ability to the Raspberry Pi, it is important to
remember they are wired directly into the internal core
of the system.
 This means that they provide a very easy way to
introduce bad voltages and currents into the delicate
heart of the Raspberry Pi (this is not good and means it
is easy to break it without exercising a little care).
 http://elinux.org/RPi_Tutorial_EGHS:GPIO_Protection_Cir
cuits
 http://www.rhydolabz.com/index.php?main_page=pr
oduct_info&cPath=80&products_id=1045

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 Things we need to protect:
 1) Drawing excess current from the pins (or short-circuiting an output)
 2) Driving over-voltage on an input pin (anything above 3.3V should be
avoided). The PI has protection diodes between the pin and 3V3 and GND,
negative voltages are shorted to GND, but positive voltages greater than
3V3 + one "diode drop" (normally 0.5V) will be shorted to 5V, this means that
if you put a 5V power supply on the GPIO pin you will "feed" the 3V3 supply
with 4.5 Volt (5V - the diode drop) and that may damage 3V3 logic if the 5V
source succeeds in lifting the PI's 3V3 supply to an unsafe value. Note that if
you limit the current (for example with a 10K resistor) the small amount of
current flowing into the 3V3 supply will probably do no harm.
 3) Static shocks, from touching pins without suitable grounding (often called
ESD - ElectroStatic Discharge, occurs when your clothes etc build up an
electrical charge as you move around)
 All of these can potentially break your Raspberry Pi, damage the GPIO
circuits or weaken it over time (reducing its overall life).

4. Mayank Joneja
GPIO in Python
 The RPi.GPIO python module offers easy access to the GPIO
 The GPIO module comes pre-installed in Raspbian.
 However, in the rare case that you end up flashing a really old image on your SD card, I
guess you’ll need to install/download the RPi.GPIO module
 sudo apt-get update
 sudo apt-get install python-dev
 sudo apt-get install python-rpi.gpio

5. Mayank Joneja
BCM or BOARD
 There are 2 ways of numbering the IO pins on the 26 pin header on a Raspberry Pi within RPi.GPIO
 BOARD Mode
 This refers to the pin numbers on the P1 header of the Raspberry Pi board
 Advantage:
 Your hardware will always work, regardless of the board revision of the RPi
 You won’t need to rewire your connector or change your code
 BCM Mode:
 Lowest level way of working
 It refers to the channel numbers on the Broadcom SoC
 Disadvantage:
 You will always have to work with a diagram of which channel number goes to which pin on the RPi board
 Your script could break between revisions of the RasPi boards.

6. Mayank Joneja
Pinout

7. Mayank Joneja
Condensed Version

8. Mayank Joneja
 To specify which you are using:
GPIO.setmode(GPIO.BOARD) or GPIO.setmode(GPIO.BCM)

9. Mayank Joneja
Hookup an LED
 Connect the +ve pin of the LED to 3.3V via a resistor
 Connect the –ve pin of the LED to Ground

10. Mayank Joneja
Blink!
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7,GPIO.OUT)
GPIO.output(7,True) #to switch on,
#GPIO.output(7,False) #to switch off
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(4,GPIO.OUT)
GPIO.output(4,True) #to switch on,
#GPIO.output(4,False) #to switch off

11. Mayank Joneja
 To prevent warnings:
 GPIO.setwarnings(False)
 Delay Library:
 time.sleep

12. Mayank Joneja
The real Blink!
import RPi.GPIO as GPIO
from time import sleep
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7,GPIO.OUT)
while(True):
GPIO.output(7,True) #to switch on,
sleep(1) #stay on for 1 second
GPIO.output(7,False) #to switch off
sleep(1) #stay off for 1 second

13. Mayank Joneja
Pulse Width Modulation
 PWM is one of the most commonly
used techniques of achieving a wide
range of output voltages on a digital
output pin
 Applications:
 Controlling the brightness of an LED
 Speed Control of motors
 Driving Servo motors (Position control)

14. Mayank Joneja
PWM on the Pi
import RPi.GPIO as GPIO
from time import sleep
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7,GPIO.OUT)
while(True):
for n in range (0,3000):
#90 % duty cycle
GPIO.output(7,True) #to switch on,
sleep(0.010) #stay on for 0.010 second
GPIO.output(7,False) #to switch off
sleep(0.000) #stay off for 0.000 second (what ? I’m making a point you know :P)
for n in range (0,3000):
#10 % duty cycle
GPIO.output(7,True) #to switch on,
sleep(0.001) #stay on for 0.001 second
GPIO.output(7,False) #to switch off
sleep(0.009) #stay off for 0.009 second
The LED glows bright at a 100%
duty cycle first and then dull at
a 10% duty cycle.
The on/off switching is so fast,
that the human eye can’t see
the flickering/blinking at this
frequency due to persistence
of vision

15. Mayank Joneja
Buttons!
 The simplest input device is a push button
(also called a micro switch)
 A push button maintains an electrical
connection between its terminals as long
as the button is pressed
 When the button is pressed, a connection
is created between T1(or T1’) and T2
or(T2’)

16. Mayank Joneja
Pulling up/down a pin
 Many times, when nothing is connected to a micro-controller input pin, they remain in a
state of high impedance (HiZ)
 This can be interpreted as either 1 or 0 randomly by the micro.
 In order to avoid this unwanted input, Pull up or pull down resistances are used to force
the pin to a state (VCC or GND) depending on the connection of the pushbutton.
 Pull up involves connecting the pin to VCC via a big resistance like 10k Ohm
 Pull down involves connecting the pin to GND via a big resistance like 10k Ohm
 In either case, the resistor limits the current drawn from the power supply and ensures that
the path through the switch is ,electrically, the path of least resistance for current to flow
through once the switch is pressed.

17. Mayank Joneja
Connections for pull down

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Giggles
import RPi.GPIO as GPIO
from time import sleep
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BOARD)
GPIO.setup(11,GPIO.IN)
while True:
mybutton = GPIO.input(11)
if mybutton == True:
print ‘giggle’
#Debouncing ??
sleep(0.2)
Press [CTRL]+[C] to terminate
execution via keyboard interrupt
when you’re done 

19. Mayank Joneja
POP QUIZ (ominous thunder..)
 Write a small code to replicate the switch’s state on the LED (on if pressed, off if not) with:
 GPIO 7 as o/p LED, and 11 as i/p switch

20. Mayank Joneja
import RPi.GPIO as GPIO
from time import sleep
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BOARD)
GPIO.setup(11,GPIO.IN)
GPIO.setup(7,GPIO.OUT)
while True:
mybutton = GPIO.input(11)
if mybutton == True:
GPIO.output(7,True)
else:
GPIO.output(7, False)
#Debouncing ??
sleep(0.2)

21. Mayank Joneja
Scratch
 Scratch is an educational programming language and multimedia authoring tool
 Excellent first language
 Allows you to make interesting games
 GPIO Access on the Raspberry Pi
 http://cymplecy.wordpress.com/2013/04/22/scratch-gpio-version-2-introduction-for-
beginners/

22. Mayank Joneja
WebIOPi
 The Internet of Things (IoT) refers to uniquely identifiable
objects and their virtual representations in an Internet-like
structure
 WebIOPi is developed and tested on Raspbian
 Only dependency is Python 2.7 or 3.2
 https://learn.adafruit.com/raspberry-pi-garage-door-
opener/web-io-pi
 Cool Project: https://learn.adafruit.com/raspberry-pi-garage-
door-opener/web-io-pi-configuration
wget http://webiopi.googlecode.com/files/WebIOPi-0.6.0.tar.gz
tar xvzf WebIOPi-0.6.0.tar.gz
cd WebIOPi-0.6.0
sudo ./setup.sh

23. Mayank Joneja
 sudo python –m webiopi 8000
 8000: the port number
 Connect the Raspberry Pi to the network
 Open a browser and go to http://RaspberryPiIP:8000/
 RaspberryPiIP refers to the IP of you Pi eg:192.168.1.10
 You can even add a port redirection on your router and/or use IPv6 to control the GPIO
pins over the internet !

24. Mayank Joneja
Running WebIOPi
 User is “webiopi”
 Password is “raspberry”
 Glow LED, press Switch
 By choosing the GPIO Header Link on the main page, you will be able to control the GPIO
using a web UI
 Click the out/in button to change the direction
 Click the pins to change the GPIO o/p state