Getting Started with Raspberry Pi Tom Paulus www.tompaulus.com @tompaulus 

Recommended

Hardware 

Model B 

Model A 

Raspberry

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Arduino

UNO MEGA DUE Pi Model A Pi Model B Operating Voltage 5 V 5 V 3.3 V 3.3 V 3.3 V SRAM 2 KB 8 KB 96 KB 265 MB 512 MB FLASH- Memory 32 KB 256 KB 512 KB up to 64 MB up to 64 MB Clock Speed 16 MHz 16 MHz 84 MHz 700 MHz* 700 MHz* USB Host n/a n/a 1 1 2 Network n/a n/a n/a n/a 10/100 wired Ethernet RJ45 Audio / Video n/a n/a n/a HDMI, Composite Video, TRS-audio jack HDMI, Composite Video, TRS-audio jack Current I/O pins 40 mA 40 mA total 130 mA 2 to 16 mA 2 to 16 mA Digital I/O Pins 14 (6 PWM) 54 (15 PWM) 54 (12 PWM) 17 (1 PWM) 17 (1 PWM) Analog Input Pins 6 16 12 2DAC Analog Out 0* 0* Price $30 $59 $50 $25 $35 

Initial Setup 

Recommended

http://www.raspberrypi.org/downloads 

1. Download and Unzip the .zip from www.raspberrypi.com 2. Format the SD Card to clear all Data 3. Drag & Drop the contents of the .zip onto the SD Card Install Your OS 

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Demo 

GPIO 

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sudo apt-get install python-dev python-pip sudo easy_install -U distribute sudo pip install RPi.GPIO Preparing

Simple

! from time import sleep import RPi.GPIO as GPIO GPIO.setmode(GPIO.BCM) #use the common numeration, #also the one found on the Adafruit Cobbler led = 21 # GPIO Port to which the LED is connected delay = .5 GPIO.setup(led, GPIO.OUT) # Set 'led' as and Output print "Press CTRL+C to exit" try: while True: GPIO.output(led, True) # led On sleep(delay) # wait 'delay' seconds GPIO.output(led, False) # led Off sleep(delay) # wait another 'delay' seconds except KeyboardInterrupt: GPIO.output(led, False) finally: GPIO.cleanup() blink.py 

Hardware 

Demo 

Analogue

MCP3008 8-Channel 10-Bit ADC With SPI Interface RaspberryPi with ADC 

SPI requires four signals: clock (SCLK) master output/slave input (MOSI) master input/slave output (MISO) slave select (SS) or (CS) chip-select RaspberryPi Serial Peripheral Interface Bus - SPI 

pi@raspberrypi ~ $ cat /etc/modprobe.d/raspi-blacklist.conf! # blacklist spi and i2c by default (many users don't need them)! blacklist spi-bcm2708! blacklist i2c-bcm2708! ! Loading Kernel Modules: Edit the raspi-blacklist.conf, so that the spi module gets loaded, Reboot, and confirm with lsmod that ‘spidev’ and ‘spi_bcm2708’ are now loaded and ls /dev/spi* shows two spi devices: /dev/spidev0.0 and /dev/spidev0.1 ! Installing Dependencies: sudo apt-get install python-dev git-core! ! Install Python bindings for Linux SPI access through spidev: cd ~! git clone git://github.com/doceme/py-spidev! cd py-spidev/! sudo python setup.py install! ! ... which creates /usr/local/lib/python2.7/dist-packages/spidev.so SPI 

I2C SPI 

IN =[0000 0001][1CNL ----][---- ----]! (8+channel) <<4 OUT=[---- ----][---- -XXX][XXXX XXXX] (10bit)! ((r[1] & 3) << 8) + r[2] 

IN =[0000 0001][1CNL ----][---- ----]! (8+channel) <<4 OUT=[---- ----][---- -XXX][XXXX XXXX]! r[0] ((r[1] & 3) << 8) + r[2] r = spi.xfer2( [1, (8+chnnl)<<4, 0] )! return ((r[1] & 3) << 8) + r[2] 

def analogRead(port, bus=0, ce=0): """Read the given ADC port and preform the necessary shifting of bits""" spi.open(bus, ce) # CE port that the MCP3008 is connected to if (port > 7) or (port < 0): print 'analogRead -- Port Error, Must use a port between 0 and 7' return -1 r = spi.xfer2([1, (8 + port) << 4, 0]) value = ((r[1] & 3) << 8) + r[2] spi.close() return value 

import time import spidev import RPi.GPIO as GPIO # This program reads an analogue value form a potentiometer attached to port 0 on the MCP3008 Chip spi = spidev.SpiDev() pot_adc = 0 statusLED = 23 # GPIO port that our Status led is connected to GPIO.setmode(GPIO.BCM) GPIO.setup(statusLED, GPIO.OUT) print "Press CTRL+C to exit" try: while True: GPIO.output(statusLED, True) # Status Led On print analogRead(pot_adc) # Print read value time.sleep(.125) # Wait a little GPIO.output(statusLED, False) # Status Led Off time.sleep(.175) # Wait a bit longer except KeyboardInterrupt: GPIO.output(statusLED, False) finally: GPIO.cleanup() ADC1.py 

Hardware 

But, That’s Just Ugly! 

Let’s Add a Display 

I2C connects the same two signal lines to all slaves. I.e. addressing is required and all devices need a unique address SDA - Serial Data SCL - Serial Clock RaspberryPi Inter-IC Bus - I2C 

pi@raspberrypi ~ $ cat /etc/modprobe.d/raspi-blacklist.conf! # blacklist spi and i2c by default (many users don't need them)! blacklist spi-bcm2708! blacklist i2c-bcm2708! ! Loading Kernel Modules: - Edit the raspi-blacklist.conf, so that the i2c module gets enabled. - Add the following lines to /etc/modules i2c-dev i2c-bcm2708 Reboot, and confirm ls /dev/i2c* shows /dev/i2c-0 /dev/i2c-1 ! Installing Dependencies: sudo apt-get install python-smbus i2c-tools! ! With i2c devices connected, run somthing like this, to discover devices addresses. sudo i2cdetect -y 0 I2C 

I2C SPI 

! import time import spidev import RPi.GPIO as GPIO from lib.Char_Plate.Adafruit_CharLCDPlate import Adafruit_CharLCDPlate import smbus GPIO.setwarnings(False) GPIO.setmode(GPIO.BCM) lcd = Adafruit_CharLCDPlate() spi = spidev.SpiDev() pot_adc = 0 # ADC l = list() # List for Light Sensor Averaging statusLED = 23 print "Press CTRL+Z to exit" GPIO.setup(statusLED, GPIO.OUT) lcd.backlight(lcd.ON) lcd.clear() ! def movavg(list, length, value): """A function that smooths the results by averaging a list""" list.append(value) if length < len(list): del list[0] sum = 0 for x in list[:]: sum += x return sum / len(list) ADC2.py 

try: while True: # Change the Back-light based on what button has been pressed if lcd.buttonPressed(lcd.DOWN): lcd.backlight(lcd.ON) if lcd.buttonPressed(lcd.UP): lcd.backlight(lcd.OFF) lcd.home() GPIO.output(statusLED, True) # Status Led On lcd.message('Potentiometer:\n' + str( movavg(l, 4, analogRead(pot_adc))) + ' ') # Read analog value sleep(.1) # Wait a little GPIO.output(statusLED, False) # Status Led off sleep(.155) # Wait a bit longer except KeyboardInterrupt: GPIO.output(statusLED, False) spi.close() finally: lcd.clear() lcd.backlight(lcd.OFF) GPIO.cleanup() ADC2.py 

MORE Inputs!! 

ADC3.py def colorChange(channel): global color if channel == green: if color == lcd.ON: color = lcd.GREEN elif color == lcd.GREEN: color = lcd.OFF else: color = lcd.ON for i in range(3): lcd.backlight(color) sleep(.01) sleep(bounce/1000) 

try: GPIO.add_event_detect(green, GPIO.RISING, callback=colorChange, bouncetime=bounce) while True: GPIO.output(statusLED, True) # Status Led On l = movavg(light_Average, 4, analogRead(light_adc)) # Read the light sensor lcd.home() lcd.message('Pot: ' + str(analogRead(pot_adc)) + ' \nLight: ' + str(l) + ' ') GPIO.output(statusLED, False) # Status Led Off sleep(rate) # Wait a little except KeyboardInterrupt: GPIO.output(statusLED, False) spi.close() finally: lcd.clear() lcd.backlight(lcd.OFF) GPIO.cleanup() ADC3.py 

Hardware 

Demo 

Why? try: # Main Program except KeyboardInterrupt: # On Interrupt finally: GPIO.cleanup() 

Somewhere, there is an Arduino laughing... Current I/O pins 40 mA Digital I/O Pins 14 (6 PWM) Analog Input Pins 6 Price $30 

Using

JSON 

JavaScript

JSON

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What

#! /usr/bin/python #Written By Tom Paulus, @tompaulus, www.tompaulus.com import requests import time timeURL = 'http://json-time.appspot.com/time.json?tz=' zone = 'America/Los_Angeles' while True: timeJson = requests.get(timeURL + zone).json() hour = timeJson['hour'] minute = timeJson['minute'] second = timeJson['second'] dateTime = timeJson['datetime'] print str(hour) + ':' + str(minute) + ':' + str(second) print dateTime time.sleep(1) time.py 

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Displaying

Weather Client 

while True: if update: lcd.clear() lcd.message('Please Wait\nFetching Data') json = API.getLocation(locations.get(str(location) + 's'), locations.get(str(location) + 'c'), token) update = False display = 0 if display == 0: lcd.clear() high = API.high(json, units_Temp) low = API.low(json, units_Temp) windSpeed = API.windSpeed(json, units_Speed) windDir = API.winDir(json) string1 = API.Display1(high, low, windSpeed, units_Speed, windDir, language) lcd.message(string1) if display == 1: lcd.clear() rain = API.rain(json) humidity = API.humidity(json) string2 = API.Display2(rain, humidity, language) lcd.message(string2) if display == 2: lcd.clear() lcd.message('More Data\nComing Soon!') Main.py 

class WebAPI: ! def getLocation(self, state, city, token): d = requests.get( 'http://api.wunderground.com/api/' + str(token) + '/forecast/q/' + str(state) + '/' + str(city) +'.json') json = d.json() return json def high(self, json, units): high = str(json['forecast']['simpleforecast']['forecastday'][0]['high'][units]) return high def low(self, json, units): low = str(json['forecast']['simpleforecast']['forecastday'][0]['low'][units]) return low def windSpeed(self, json, units): windSpeed = str(json['forecast']['simpleforecast']['forecastday'][0]['avewind'][units]) return windSpeed def winDir(self, json): windDir = str(json['forecast']['simpleforecast']['forecastday'][0]['avewind']['dir']) return windDir WUndergroundAPI.py 

USER Data!! NSA I have some data for you... 

User Data... Main.py app_info_folder = '/etc/WeatherUnderground' LocationData = app_info_folder + '/locations.conf' try: info = open(LocationData) data = info.readlines() length = int(str(data).count(',')) + 1 l1 = data[0].split(',') for x in range(0, length): l2 = l1[x].split(':') locations[str(x) + 's'] = l2[0] locations[str(x) + 'c'] = l2[1] info.close() except IOError: lcd.message('Welcome\nNew User!') print 'Adding New Location...' State = raw_input('Enter The name of the State your desired location is in, using the abbreviation -CA\n') City = raw_input('Now, Enter the name of the City\n') print '\nThank You!' State = State.upper() City = City.capitalize() if not os.path.exists(app_info_folder): os.makedirs(app_info_folder) info = open(LocationData, 'w') info.write(State + ':' + City) locations = {'0' + 's': State, '0' + 'c': City} info.close() 

User Data... AddLocation.py app_info_folder = '/etc/WeatherUnderground' LocationData = app_info_folder + '/locations.conf' info = open(data) State = raw_input('Enter The name of the State your desired location is in, using the abbreviation -CA\n') City = raw_input('Now, Enter the name of the City\n') print '\nThank You!' State = State.upper() City = City.replace(' ','_') if raw_input("Is this Information Correct? Type 'y'\n") == 'y': info = open(data, 'a') info.write(',' + State + ':' + City) info.close() 

Demo 

Summary Wow! We have learned a lot!! 1. Initial Setup of the Raspberry Pi 2. Made a little LED blink 3. Dealt with an Analog Value and Displayed it 4. The Basics of JSON 5. Got our feet wet by finding the Time in different places 6. Used our new Knowledge to find the Weather 7. Learned how to save Custom User Data 

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Slides: Code Used in this Talk: http://tompaulus.com/talks https://github.com/tpaulus/SCC-USC2013 Email: [email protected]