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

Recommended

Hardware 

Model B 

Model A 

Model B 

Raspberry

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Arduino

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

Initial Setup 

http://www.raspberrypi.org/downloads 

Recommended

Creating Your Image 1. Download and Unzip the .img from www.raspberrypi.com 2. Format the SD Card to clear all Data Windows Users: Use Win32DiskImager Mac Users: in a Terminal-- sudo diskutil unmount /dev/disk1s1 sudo dd bs=1m if=(Insert Location of .img) of=(SD Card) sync sudo diskutil eject /dev/rdisk1 

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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

#! /usr/bin/python import time import RPi.GPIO as GPIO GPIO.setmode(GPIO.BCM) #use the common numeration, #also the one found on the Adafruit Cobbler led = 25 delay = .5 GPIO.setup(led, GPIO.OUT) #Set 'led' as and Output while True: GPIO.output(led, True) #led On time.sleep(delay) #wait 'delay' seconds GPIO.output(led, False) #led off time.sleep(delay) #wait another 'delay' seconds 

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Demo 

Analogue

MCP3008 8-Channel 10-Bit ADC With SPI Interface Ra!berryPi wi" ADC 

SPI requires four signals: clock (SCLK) master output/slave input (MOSI) master input/slave output (MISO) slave select (SS) or (CS) chip-select Ra!berryPi Se#al Pe#pheral 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] 

#! /usr/bin/python #Written By Tom Paulus, @tompaulus, www.tompaulus.com import time import spidev import RPi.GPIO as GPIO spi = spidev.SpiDev() light_adc = 7 statusLED = 25 GPIO.setmode(GPIO.BCM) GPIO.setup(statusLED, GPIO.OUT) print "Press CTRL+Z to exit" def analogRead(port): """Read the given ADC port and preform the necessary shifting of bits""" spi.open(0, 0) 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 while True: GPIO.output(statusLED, True) print analogRead(light_adc) time.sleep(.125) GPIO.output(statusLED, False) time.sleep(.175) 

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Demo 

Analogue

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 Ra!berryPi 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 

#! /usr/bin/python #Written By Tom Paulus, @tompaulus, www.tompaulus.com import time import spidev import RPi.GPIO as GPIO from Adafruit_LEDBackpack.Adafruit_7Segment import SevenSegment import smbus GPIO.setmode(GPIO.BCM) segment = SevenSegment(address=0x70) # which port the display is spi = spidev.SpiDev() light_adc = 7 l = list() statusLED = 25 print "Press CTRL+Z to exit" GPIO.setup(statusLED, GPIO.OUT) def analogRead(port): """Read the given ADC port and preform the necessary shifting of bits""" spi.open(0, 0) 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 

def movavg(list, length, value): """A function that smooths the results by averaging a list""" #Courtesy Wolf Paulus list.append(value) if length < len(list): del list[0] sum = 0 for x in list[:]: sum += x return sum / len(list) while True: GPIO.output(statusLED, True) segment.writeInt(movavg(l, 4, analogRead(light_adc))) time.sleep(.125) GPIO.output(statusLED, False) time.sleep(.175) **This program uses a modified library** 

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Demo 

Using

JSON 

JavaScript

JSON

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What

#! /usr/bin/python #Written By Tom Paulus, @tompaulus, www.tompaulus.com import lib.requests as requests import time timeURL = 'http://json-time.appspot.com/time.json?tz=' zone = 'America/Phoenix' 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) 

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Displaying

News Client 

class Scroller(): def splitString(self, s, lineLength): # s = 'The Quick Brown Fox Jumps Over The Lazy Dog' #Test String string = '' length = 0 k = 0 #Counter Variable wordLength = list() strings = list() lines = list() words = s.strip().split() for k in range(0, len(words)): #Make a list of the word lengths length = len(words[k]) wordLength.append(length) k = 0 #Reset Counter while k < len(words): if len(string) + len(words[k]) + 1 < lineLength: if len(string) == 0: string += words[k] else: string = string + ' ' + words[k] k += 1 else: strings.append(string) string = '' if k == len(words): strings.append(string) string = '' k = 0 #Reset Counter 

while k < len(strings): #Format for Our Display if k == len(strings) - 1: line = strings[k] lines.append(line) break else: line = strings[k] + '\n' + strings[k + 1] lines.append(line) k += 2 return lines if __name__ == '__main__': s = raw_input('Enter the string to be separated\n').replace('\n', '') tools = Scroller() print tools.splitString(s, 16) 

The Quick Brown Fox Jumps Over The Lazy Dog ['The Quick Brown\nFox Jumps Over', 'The Lazy Dog'] 

class NewsAPI: def get(self,count,key): """ Get the homepage form HackerNews :return: JSON object """ url = 'http://api.usatoday.com/open/articles/topnews/news?count='+str(count)+'&days=0&page=0&encoding=json&api_key='+key d = requests.get(url) JSON = d.json() return JSON while True: z = 0 if update: nJson = API.get(15, API_KEY) length = len(nJson['stories']) for x in range(0, length): articles.append(nJson['stories'][x]['title']) update = False display = tools.splitString(articles[currentTitle], 16) for y in range(0, len(display)): z += 1 Timer(y * 2, rotate, args=[display[y]]).start() time.sleep(z * 2 + 2) currentTitle = (currentTitle + 1) % len(articles) 

Demo 

Wea"er 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!') 

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 

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. What’s new in the News? 

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Slides: Code Used in this Talk: http://tompaulus.com/talks https://github.com/tpaulus/DCC-April13 Email: [email protected] 

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