Introduction to Raspberry PI

Raspberry Pi is a mini computer. It is basically a cheap PC for learning purposes and practising programming. Raspberry is just like apple a name of fruit, Pi stands for python interpreter which is provided. Price of PI 3 about 35 dollars, PI zero W only 5 dollars

Raspberry PI zero W specs

  • Size : 65mm x 30mm
  • 1GHz single core processor
  • 512 MB RAM
  • Wireless
  • 40 GPIO Pins
  • mini HDMI port
  • mini USB Port
  • SD card area
  • Camera Connector

Installing The OS

  1. Head to download page and download the image of raspbian image or use NBOOS.
  2. Format the SD Card (min 8G SD card)
  3. Burn the image on the SD card for linux 
    sudo dd if=file.img of=/dev/sdx

  4. Add SD card to the board
  5. Connect Mouse/Keyboard
  6. Connect the display
  7. Connect the power (5V DC 1 or 2A)

You can can see more details setting up your pi here.

Pi Desktop

At first you will have the Pi wizard

System is installed with some interesting applications

  • Programming

  • Some games

  • Other accessories

  • Terminal

Controlling Pi remotely

Actually you don’t have to connect the display, mouse and keyboard every time. You can enable ssh and access pi through any other computer.

Using SSH

  1. Open the terminal
  2. Type 
     sudo raspi-config

  3. Use arrows to open Interfacing options and enable SSH (Remote command line access)

Or basically you can enable it from preferences and Raspberry pi configuration

  • To access raspberry pi from your computer install ssh
sudo apt-get install ssh 
ssh pi@192.168.1.200 # Or the IP of your PI
  • For windows users you can use PuTTY. Check this link for more help

Use VNC

  1. Install VNC on your computer here
  2. Install VNC on your pi check this

Make sure you enabled VNC.

  1. Open pi from your computer using its IP

And now you can work from your computer

Basic linux commands

Operating system of raspberry pi is based on linux. Here some basic commands

Command Meaning
ls List files in current directory
cd Change directory
pwd print working directory
rm filename remove filename
mkdir directoryname Make directory named directoryname
rmdir directoryname remove empty directory
mv oldfile newfile Move (rename) oldfile to newfile
cp oldfile newfile Copy oldfile to newfile
man command Display manual of command
date read system date/time
sudo perform as root user
./program run program
exit Quit terminal session

Getting started with python

Python is interpreted high level programming language for general purpose computing.

Variables

Python is untyped language

x = 5
y = 'Hello SBME'

Lists

# Initialize the list
myList = [2, 55, 565]

# add an element
myList.append(8)

print( myList ) # ??
print( myList[0] ) # ??
print( myList[3] ) # ??
print( myList[4] ) # ??

Arithmetic Operations


x = 19
y = 18 

z = x / y
z = x * y
z = x + y
z = x - y

Comparison Operators

operator meaning
== Equal to
!= Not equal to
< Less than
> Greater than
<= Less than or equal to
>= Greater than or equal to

Logical Operations

x = True
y = False 

x or y 
x and y 
not x

If, elif, else


x = 25 
y = 20 

if x < y:
    print("y is greater than x")
elif x == y:
    print("x and y are equal")
else:
    print("x is greater than y")

Loops


for i in range(10):
  print( i )

i = 0
while i < 10 :
  print( i )
  i += 1

Functions

def mean( list ):
  sum = 0
  for element in list:
    sum += element
  return sum / len( list )

m = mean([1,12,42,1,23,12])
print( m )

Importing Libraries

import numpy as np
from gpiozero import LED

Pi physical computing with python

Full tutorial is available here

GPIO

Pi has 40 Pins

Note

  • Using 5V to drive something like motors could destroy the board
  • Maximum input for GPIO pins is 3.3V. 5V could destroy the board

Lighting a LED

  1. Open python3

just type on terminal

$ python3

or you python IDLE3

  1. Connect the led to GPIO17
  2. Code 
    >>from gpiozero import LED
>>led = LED(17)
>>led.on()
>>led.off()

Blinking example

  1. Make a new file blink.py

you can use nano editor or vim.

$nano blink.py

or

$vi blink.py
  1. Add your code
from gpiozero import LED
from time import sleep

led = LED(17)

while True:
    led.on()
    sleep(1)
    led.off()
    sleep(1)
  1. Run the example
$python3 blink.py

Using Buttons

Connect the button

from gpiozero import Button

button = Button(2)
button.wait_for_press()
print('You pushed me')

Toggle the led with the button

from gpiozero import LED, Button
from signal import pause

led = LED(17)
button = Button(2)

button.when_pressed = led.on
button.when_released = led.off

pause()

More examples

You will find more examples for different hardware interfaces in the tutorial link. The library supports

from gpiozero import Buzzer, TrafficLights, LightSensor, MotionSensor, DistanceSensor

Analog inputs

All GPIO pins of pi are digital. To connect pi with analog sensors you have to use an ADC to make it digital. Communication for analog is using SPI protocol.

They recommending the usage of 8 channels ADC MCP3008

This is the connection with Pi

And you have another 8 pins to connect the analog device like potentiometer

Code

from gpiozero import MCP3008
# Potentiometer is connected to channel 0
pot = MCP3008(0)
# Get the analog value
print(pot.value)

Using motors

Use H bridge and Pi to control the motor 

from gpiozero import Motor

# Initialization
motor1 = Motor(4, 14)
motor2 = Motor(17, 27)

# Move forward with full speed
motor1.forward()
# Move forward with half speed
motor1.forward(0.5)
# Move backward with half speed
motor2.backward(0.5)
# Reverse 
motor1.reverse()
# Stop
motor1.stop()

Two wheeled Robot

from gpiozero import Robot
# Initialize it 
robot = Robot((4, 14), (17, 27))
# All movements 
robot.forward()
robot.backward()
robot.reverse()
robot.right()
robot.left()
robot.stop()