Create a Simple Home Monitoring Device

Class Introduction

Welcome
Thank you for enrolling and welcome to class
Where to Get Help
Please share questions on the Community section for the class so others can benefit.

You are welcome to email me at:

sidwarkd@hardlysoftware.com
What We Will and Won't Cover
We Will Cover:
- Setup and Configuration of the Pi
- Basic I/O
- SPI
- I2C
- Connecting to Twitter
We Won't Cover:
- In depth electronics
- How to program
Start Thinking of Your Student Project
Create your student project. Even if you haven't settled on one you can still create a draft version of it that you can edit later.

Setting Up Your Pi

Download NOOBS
You can download NOOBS from the Raspberry Pi website:

http://www.raspberrypi.org/downloads
Format SD Card
On Windows and Mac use the SD Card Formatting tool. For Linux it is recommended that you use gparted and make sure to format the card as FAT32. Using FAT16 will not work.
Prepare your SD Card with NOOBS
Once formatted all you have to do is copy the downloaded NOOBS files to your SD card. Remember to copy the contents of the NOOBS folder to the SD card and not the top level folder.
Unbox and Hook Up Pi
Connect power, ethernet, a keyboard and video source to your Pi. You can optionally install your Pi in a case but it is not required for this project. If you do use a case make sure you have easy access to the header pins.

Safety Tip: If you are not using a case make sure you don't put your Pi on a surface that can conduct electricity like metal. Doing so will likely ruin your Raspberry Pi.

Time Saver: I recommend using a surge protector with a switch if you have one. Plug your Pi into that and then you can turn it on and off via the surge protector switch instead of having to plug/unplug from the wall. If you don't have one I recommend connecting and disconnecting your Pi from the outlet end and not using the connector on the board.
Install Raspbian
Insert the prepared SD card into the Raspberry Pi. Make sure it is all the way in and power up your Pi.

From the NOOBS menu use the keyboard arrow keys to highlight Raspbian and the spacebar to select it. Once selected press 'i' to begin the installation process.

Time Saver: While Raspbian is installing you can use the 'l' key to bring up the language menu and '9' to set the keyboard layout. Doing so during the install will save you from having to do it later.
Add WiFi Adapter (Optional)
If you have a USB WiFi adapter for your Raspberry Pi you should install it now. While internet access is required for the class project it does not have to be via WiFi. Leaving the ethernet cable connected will work just fine.
Test Internet Connection
We will need access to the internet for this project. If you are using a WiFi dongle make sure it is configured and working at this point before continuing.

ping google.com
Test SSH (Optional)
If you want to SSH into your Pi to work on the class project you should test that now. If you want to continue using the monitor and keyboard you can skip this project step.

Default credentials for Raspbian are:

username: pi

password: raspberry
Update your Pi
This will ensure that everything is up to date before you begin on your project.

sudo apt-get update

sudo apt-get upgrade

The GPIO Header

Locate the GPIO Header
Identify Pi Revision
Board Revision History
How Pins are Numbered
When looking at the header vertically the pins are numbered like you read a book; left to right, top to bottom.
Label Header Pins
Select one of the methods described in the video or choose your own. Either way it is very important not to get the pins mixed up as you can easily ruin your Pi.
Setup Your Testbed
Whether you use jumper wires or a cable to make connections, now is a good time to get your Pi and breadboard set up in a location that is well lit and easily accessible.
Understand Pin Do's and Don'ts
DO:
- Use female jumper wires
- Verify the board revision
- Verify connections before making them
DON'T:
- Make connections while Pi is turned on
- Connect 5V to the I/O pins
- Touch the header while powered on

Setup Input and Output

Verify Python is installed
From the command line type python --version. This class will be using version 2.7.3.
Install python-dev package
sudo apt-get install python-dev
Test RPi.GPIO
We can test the library by getting the board revision. Launch a python shell with sudo python and then do the following commands:

import RPi.GPIO as GPIO

GPIO.RPI_REVISION

Output: Hello LED

Understand the 2 Ways to Connect an LED
The Pi output pin can be the voltage source or the ground source.
Plan Breadboard Layout of LED Circuit
I use Fritzing to mock up my circuits before connecting them. This helps me verify the connections and see how much space things will take up.
Make LED Connections
For more information about LEDs and connecting them check out this site.
Understand GPIO.BOARD vs GPIO.BCM
Referencing the header pins in GPIO.BOARD mode will work on any version of the Pi because it simply refers to the physical pin number. Using GPIO.BCM mode requires you to reference the correct pin name based on the board revision you are using.

We will use GPIO.BOARD mode for this class.
Use RPi.GPIO to turn the LED on/off
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)

GPIO.setup(12, GPIO.OUT)

GPIO.output(12,1)

GPIO.output(12,0)

Input: Add a Switch and Button

Understand Switch and Button Connections
We use the switch to simply connect the input pin to 3.3V which is a digital 1 or to ground which is a digital 0. Remebering that a button is just a momentary switch will allow us to use the same circuit design for our button that we use for our switch.
Connect Switch
Make sure your Raspberry Pi is turned off.
Test Switch Functionality
Verify the that switch is working as we expected.
Create monitor.py
For the rest of the class I'll be using nano text editor for editing this file. If you've never used it before it might help to check out the Quick Guide to nano.
Make Switch Control LED
For this step you will modify the code to have the switch turn the LED on and off.
Connect Button
Connect the button in the same way we connected the switch.
Test Button
With the button connected we need to test the switch. We add a software "debounce" to avoid triggering the push code multiple times.

Solder Break

Make Headers for Temp and Display Modules
If you have male headers available I recommend using them on the breakout boards of the temp and display modules however hookup wire works just fine if it's all you have.
Solder Headers to Temp Board
Don't let this scare you. If you've never soldered before that's alright. You can do this! Read the tutorial linked in the Resource section below and take your time.
Solder Header to Display Board
Remember NOT to solder the 2-pin header used to level the board for soldering.

Setup SPI

Gain Basic Understanding of SPI Protocol
Think of the SPI protocol like you would any other standard protocol like USB or Thunderbolt. It requires certain physical connections (MOSI, MISO, CLK, etc) and then follows a certain specification. The most important points to remember are:
- It's a Master/Slave Protocol
- There are different clock modes available
- Speed is controlled by the Master
- You have to write a byte to read a byte
Download and Compile SPI Test Program
wget https://raw.github.com/torvalds/linux/master/Documentation/spi/spidev_test.c gcc -o spidev_test spidev_test.c ./spidev_test -D /dev/spidev0.0
Try the Loopback Test
Don't forget to connect the MOSI pin to the MISO pin on the pi. ** Always unplug the Pi before making connections **
Remove SPI From Blacklist
The file to modify is /etc/modprobe.d/raspi-blacklist.conf
Reboot Pi
sudo reboot
Confirm SPI Test Works
This time when you run the loopback test you should get a block of data.

Add the Display

Review Display SPI Info
We need to know what connections to make, what mode to run in, speed limitations, and power requirements. See the Resource section below for a link to the datasheet.
Connect Display to Breadboard
** Turn off the Pi before making connections **
Send Data to Display Using Echo
echo -ne "\x01\x02\x03" > /dev/spidev0.0
Clear the Display Using Echo
echo -ne "\x76" > /dev/spidev0.0
Install spidev Module
The links for the two files are:

https://raw.github.com/doceme/py-spidev/master/spidev_module.c

https://raw.github.com/doceme/py-spidev/master/setup.py
Test spidev Module
To test via the python shell use the code below:

import spidev

spi = spidev.SpiDev()

spi.open(0,0)

spi.xfer2([0x01,0x02,0x03])

spi.xfer2([0x76])

spi.close()
Write spi_send Function
For this step you need to write a function called spi_send that will allow us to send data to modules using the SPI protocol.
Write clear_display Function
To make clearing our display easy we'll write a function that we can use.
Add Time Display Functionality
As part of the class project we want to show the current time on the display. In this step you will write the code to do that.
Set Timezone
Use tzselect from the terminal to figure out what to add to your .profile file
Enable Colon Display
spi_send([0x77, 0x10])

Configuring I2C

Learn Basics of I2C Protocol
Think of the I2C protocol like you would any other standard protocol like USB or Thunderbolt. It requires certain physical connections (SDA, SCL, power) and then follows a certain specification. The most important points to remember are:
- It's a Master/Slave Protocol
- All slaves need a unique address
- Speed is controlled by the Master clock
- Multiple devices can share the same 2 lines
Add I2C to Startup Modules
Added the following lines to /etc/modules:

i2c-bcm2708

i2c-dev
Remove I2C From Blacklist
In /etc/modprobe.d/raspi-blacklist.conf comment out the I2C line with a #
Install python-smbus and i2c-tools Packages
sudo apt-get install python-smbus

sudo apt-get install i2c-tools
Reboot Raspberry Pi
sudo reboot

Install the Temperature Sensor

Review Sensor Datasheet
TMP102 Datasheet
Hook up Sensor
Verify Sensor is Connected
sudo i2cdetect -y 1
Test Sensor Communication
Using the python shell, verify that we can retrieve data from our temperature sensor.
Add Function to Get Temperature
We'll need to rely heavily on the datasheet for this one as we'll need to manipulate the return value into the correct format.
Show Temp on SPI Display
Write a function that will take a temperature reading and put it on the display.

Don't Move! Add Motion Detector

Review Motion Sensor Datasheet
Motion Sensor Datasheet
Hookup Motion Sensor
Add Motion Detection to Script
We want our switch to "arm" the system and use the LED to let us know if it detected motion while we were gone.
Test Motion Sensor Functionality
Run the script with your code changes and verify that everything works as expected. Test the monitor in "home" and "away" mode.

Make it Tweet

Create Twitter Account For Device (Optional)
Only do this if you want your device to have it's own twitter account. If you want the device to use your personal Twitter profile for tweeting you can skip this step.
Install pip
sudo apt-get install python-pip
Install Twython
In the video we use pip but you can also use easy_install or even pull it down from Github.

sudo pip install twython
Create Twitter App
Your twitter app is how your device will tweet.
Tweet Motion and Temp Reading
Use twython in the script to post a status update to your Twitter feed. You can get as creative as you want and do not have to follow the video implementation. Use your imagination.

Summary

Start Creating
Thank you so much for enrolling in this class. I hope you've enjoyed it as much as I enjoyed teaching it. Good luck and have fun creating.

Additional Resources

Learning Python

http://www.codecademy.com/tracks/python

http://www.learnpython.org/

http://learnpythonthehardway.org/book/
Physical Computing
Class Project Part List
- Raspberry Pi (power supply, SD card, keyboard, monitor, internet connection via ethernet cable or wifi adapter)
- Pi Case (optional but recommended) - Make sure you can still access the header pins.
- Breadboard (large)
- Soldering Iron and Solder (very little soldering, maybe borrow)
- Several Feet of Hookup Wire
- Pi Cobbler from AdaFruit (optional)
- 330 resistor (1)
- 1K resistor (3)
- 10K resistor (2)
- LED (any color)
- Breadboard-Mountable Switch
- Breadboard-Mountable Push Button
- Break Away Male Header Pins (optional for solding to breakout boards)
- Seven Segment Serial Display
- TMP102 Breakout Board
- PIR Motion Sensor from Parallax
To help with your shopping I've created a shopping list at Sparkfun which contains almost everything you will need. While the temp sensor and display are only sold by Sparkfun you can get the rest of the parts from any distributor like Mouser, Newark or Digikey. I love Sparkfun but recommend NOT buying breadboards from them as they are very difficult to break in.

Sparkfun Shopping List

I recommend getting the motion sensor either directly from Parallax or from Mouser.
SD Formatter from the SD Association
PuTTY for SSH on Windows
Board Revision History
Raspberry Leaf
Pi Cobbler
Simple Pin Map
RPi.GPIO Basics
RPi.GPIO Code Examples
Fritzing
Connecting LEDs
Connecting Switches to the I/O Pins
Input Interrupt and Edge Detection
Quick Guide to nano
Soldering Tutorial from Sparkfun
http://elinux.org/RPi_SPI#Loopback_test
SPI on Wikipedia
Display Datasheet
I2C on Wikipedia
Binary Operations
Python String Formatting
Twitter App Page
Twython Documentation
Cheat Sheet
Project Code on Github

Kevin Sidwar

Software Engineer + Hardware Enthusiast

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