Building the Internet of Things with Raspberry Pi

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

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 Building the Internet of Things with Raspberry Pi

General-purpose input/output pins (GPIO) • 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 Building the Internet of Things with Raspberry Pi

The Hardware Building the Internet of Things with Raspberry Pi

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

Building an Input Circuit Resistor Implements electrical resistance Reduce current flow Building the Internet of Things with Raspberry Pi

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

Building an Input Circuit - The diagram Building the Internet of Things with Raspberry Pi

Building an Output Circuit - The components 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. Building the Internet of Things with Raspberry Pi

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

Building an Output Circuit Building the Internet of Things with Raspberry Pi

Veroboard / Stripboard Building the Internet of Things with Raspberry Pi

26pin IDC ribbon cable + crimp connector Building the Internet of Things with Raspberry Pi

Shortcuts! Building the Internet of Things with Raspberry Pi

The Software Building the Internet of Things with Raspberry Pi

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

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

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

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

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

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

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

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

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

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

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

Outputs - Setup import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) GPIO.setup(12, GPIO.OUT) Building the Internet of Things with Raspberry Pi

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

Example - Bell Building the Internet of Things with Raspberry Pi

The Raspberry Pi Alarm Building the Internet of Things with Raspberry Pi

On Github github.com/nbroers/hal Building the Internet of Things with Raspberry Pi

What’s next? Building the Internet of Things with Raspberry Pi

Questions? Building the Internet of Things with Raspberry Pi

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

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

Neil Broers @nbroers neil@foo.co.za github.com/nbroers Building the Internet of Things with Raspberry Pi

Building the Internet of Things with Raspberry Pi

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