PyConZA 2014: "Building the Internet of Things with Raspberry Pi" by Neil Broers

With the advent of the low cost Raspberry Pi computer, anyone with a soldering iron and some basic Python skills can take everyday objects and transform them into fully networked, smart devices.

In this talk, I will show you how I hacked a Raspberry Pi into my home alarm system, turning my network of IP cameras into motion triggered sensors. I will show you how to build basic input and output circuits and introduce you to the RPi.GPIO Python module. We’ll talk about how you can build a RESTful server on your Raspberry Pi to enable remote access. And finally, more ideas for hacking everyday objects around the home!

No prior electronics knowledge required.

Transcript

1. Building the Internet of Things with Raspberry Pi
2. Who am I? I am a Software Developer and Architect at Energy Partners Caution – I am not an Electronic Engineer! Building the Internet of Things with Raspberry Pi
3. Building the Internet of Things with Raspberry Pi
4. Building the Internet of Things with Raspberry Pi
5. Building the Internet of Things with Raspberry Pi Model A Model B Model B+ $25 $35 $35 1 USB port 2 USB ports 4 USB ports No Ethernet 10/100 Ethernet 10/100 Ethernet SD card slot SD card slot Micro SD card slot
6. General-purpose input/output pins (GPIO) Building the Internet of Things with Raspberry Pi • GPIO pins can be configured to be input or output • Input values are readable - HIGH or LOW (3v3 or 0v) • Output values are writable/readable
7. The Hardware Building the Internet of Things with Raspberry Pi
8. Building an Input Circuit Opto-coupler / Opto-isolator Transfers electrical signals between two isolated circuits by using light Building the Internet of Things with Raspberry Pi
9. Building an Input Circuit Building the Internet of Things with Raspberry Pi Resistor Implements electrical resistance Reduce current flow
10. Pull-up / pull-down resistors • Pull-up resistors are connected to the high voltage (3.3V) • Pull-down resistors are connected to ground • Initialize an input pin to a known state when nothing is connected to it Building the Internet of Things with Raspberry Pi Pull-up resistor
11. Building an Input Circuit - The diagram Building the Internet of Things with Raspberry Pi
12. Building an Output Circuit - The components Building the Internet of Things with Raspberry Pi Transistor • Used to amplify and switch electronic signals and electrical power • A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals.
13. Building an Output Circuit - The components Relay • Electrically operated switch • Many relays use an electromagnet to mechanically operate a switch • To control a circuit by a low-power signal Building the Internet of Things with Raspberry Pi
14. Building an Output Circuit Building the Internet of Things with Raspberry Pi
15. Veroboard / Stripboard Building the Internet of Things with Raspberry Pi
16. 26pin IDC ribbon cable + crimp connector Building the Internet of Things with Raspberry Pi
17. Shortcuts! Building the Internet of Things with Raspberry Pi
18. Accessories
19. The Software Building the Internet of Things with Raspberry Pi
20. Building the Internet of Things with Raspberry Pi
21. Finding your Pi's hardware revision cat /proc/cpuinfo Code(s) Model and revision 2 Model B Revision 1.0 3 Model B Revision 1.0 + ECN0001 4, 5, 6 Model B Revision 2.0 Building the Internet of Things with Raspberry Pi
22. Software considerations • The software is the easy part! • Possible to damage the Pi • Triple check your pin configuration Building the Internet of Things with Raspberry Pi
23. Introducing RPi.GPIO • Depending on your distro, probably already installed • If not, use pip: sudo pip install rpi.gpio Building the Internet of Things with Raspberry Pi
24. Basic usage #To import the RPi.GPIO module: import RPi.GPIO as GPIO #Select the pin numbering scheme: GPIO.setmode(GPIO.BOARD) # or GPIO.setmode(GPIO.BCM) Building the Internet of Things with Raspberry Pi
25. Exit Cleanly • Inputs are safer than outputs • Shorting outputs to ground can damage the PI • Any ports not reset before script exit will remain as is • Always perform cleanup before script exits Building the Internet of Things with Raspberry Pi
26. Exit Cleanly import RPi.GPIO as GPIO # the rest of your code goes here GPIO.cleanup() # remember, a program doesn't necessarily # exit at the last line! Building the Internet of Things with Raspberry Pi
27. Inputs - Setup import RPi.GPIO as GPIO #GPIO numbering GPIO.setmode(GPIO.BCM) channel = 7 GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_UP) # or GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) Building the Internet of Things with Raspberry Pi
28. Inputs - Polling if GPIO.input(channel): print('Input was HIGH') else: print('Input was LOW') # Or, in a loop while GPIO.input(channel) == GPIO.LOW: # wait 10 ms time.sleep(0.01) Building the Internet of Things with Raspberry Pi
29. Inputs - wait_for_edge() • blocks execution until an edge is detected • GPIO.RISING, GPIO.FALLING or GPIO.BOTH GPIO.wait_for_edge(channel, GPIO.RISING) Building the Internet of Things with Raspberry Pi
30. Inputs - event_detected() • Designed to be used in a loop with other things # add rising edge detection on a channel GPIO.add_event_detect(channel, GPIO.RISING) do_something() if GPIO.event_detected(channel): print('Button pressed') Building the Internet of Things with Raspberry Pi
31. Inputs - Threaded callbacks • RPi.GPIO runs a second thread for callback functions GPIO.add_event_detect(channel, GPIO.RISING, callback=my_callback) Building the Internet of Things with Raspberry Pi
32. Outputs - Setup import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) GPIO.setup(12, GPIO.OUT) Building the Internet of Things with Raspberry Pi
33. Outputs #Set output to HIGH GPIO.output(12, GPIO.HIGH) #Set output to LOW GPIO.output(12, GPIO.LOW) #Read the state of the output GPIO.input(12) Building the Internet of Things with Raspberry Pi
34. Example - Bell Building the Internet of Things with Raspberry Pi
35. The Raspberry Pi Alarm Building the Internet of Things with Raspberry Pi
36. On Github Building the Internet of Things with Raspberry Pi github.com/nbroers/hal
37. What’s next? Building the Internet of Things with Raspberry Pi
38. Questions? Building the Internet of Things with Raspberry Pi
39. Parts list 12V input circuit: • Optocoupler: LTV-847 - http://www.mantech.co.za/ProductInfo.aspx?Item=340M0324 • Resistor: 1K Ohm - http://www.mantech.co.za/ProductInfo.aspx?Item=64M0009 Output circuit: • Resistor: 100k ohm • Resistor: 10k ohm • Transistor (NPN Transistor): P2N2222AG - http://www.mantech.co.za/ProductInfo.aspx?Item=72M3626 • Relay: EDR101A1200Z - http://www.mantech.co.za/ProductInfo.aspx?Item=35M1045 • Diode: 1N4007: http://www.mantech.co.za/ProductInfo.aspx?Item=64M0027 Extras: • 26pin IDC ribbon cable crimp connector - http://www.mantech.co.za/ProductInfo.aspx?Item=14M8762 • Ribbon cable - http://www.mantech.co.za/ProductInfo.aspx?Item=45M0001 • Single core cable • Veroboard - http://www.mantech.co.za/ProductInfo.aspx?Item=64M0010 Building the Internet of Things with Raspberry Pi
40. References Input Circuit design: http://raspberrypihobbyist.blogspot.com/2012/09/gpio-input-circuit_19.html Output Circuit design: http://raspberrypihobbyist.blogspot.com/2012/10/revision-to-relay-circuit.html RPi.GPIO wiki http://sourceforge.net/p/raspberry-gpio-python/wiki/Home/ Raspberry Pi Technical Info http://elinux.org/RPi_Low-level_peripherals GPIO quick reference http://raspi.tv/2014/rpi-gpio-quick-reference-updated-for-raspberry-pi-b Exit Cleanly http://raspi.tv/2013/rpi-gpio-basics-3-how-to-exit-gpio-programs-cleanly-avoid-warnings-and-protect-your-pi Building the Internet of Things with Raspberry Pi
41. Neil Broers @nbroers neil@foo.co.za github.com/nbroers Building the Internet of Things with Raspberry Pi