Getting Started with Raspberry Pi - USC 2013

The Raspberry Pi is a small credit-card sized linux computer. Developers and hobbyists around the world are creating miraculous applications and projects, and now you can join them. This year's presentation covers the first steps to using your Pi. From the basics, like burning your SD Card to creating a Weather Reporter, you will learn GPIO Basics and simple Python tools. Communication between other components using SPI or I2C will also be covered. It is recommended, but not required that you have a Raspberry Pi, some knowledge of Python and simple electronics.

Transcript

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

   View Slide

2. Recommended

   View Slide

3. Hardware
   

   View Slide

4. Model B
   

   View Slide

5. Model A
   

   View Slide

6. Raspberry

   View Slide

7. View Slide

8. Arduino

   View Slide

9. 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
   

   View Slide

10. Initial Setup
    

    View Slide

11. Recommended

    View Slide

12. http://www.raspberrypi.org/downloads
    

    View Slide

13. 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
    

    View Slide

14. View Slide

15. Demo
    

    View Slide

16. GPIO
    

    View Slide

17. View Slide

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

    View Slide

19. Simple

    View Slide

20. !
    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
    

    View Slide

21. Hardware
    

    View Slide

22. Demo
    

    View Slide

23. Analogue

    View Slide

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

    View Slide

25. 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
    

    View Slide

26. 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
    

    View Slide

27. I2C
    SPI
    

    View Slide

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

    View Slide

29. 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]
    

    View Slide

30. 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
    

    View Slide

31. 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
    

    View Slide

32. Hardware
    

    View Slide

33. But, That’s Just Ugly!
    

    View Slide

34. Let’s Add a Display
    

    View Slide

35. 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
    

    View Slide

36. 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
    

    View Slide

37. I2C
    SPI
    

    View Slide

38. !
    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
    

    View Slide

39. 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
    

    View Slide

40. MORE Inputs!!
    

    View Slide

41. 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)
    

    View Slide

42. 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
    

    View Slide

43. Hardware
    

    View Slide

44. Demo
    

    View Slide

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

    View Slide

46. 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
    

    View Slide

47. Using

    View Slide

48. JSON
    

    View Slide

49. JavaScript

    View Slide

50. JSON

    View Slide

51. View Slide

52. What

    View Slide

53. #! /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
    

    View Slide

54. View Slide

55. Displaying

    View Slide

56. Weather Client
    

    View Slide

57. 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
    

    View Slide

58. 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
    

    View Slide

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

    View Slide

60. 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()
    

    View Slide

61. 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()
    

    View Slide

62. Demo
    

    View Slide

63. 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
    

    View Slide

64. View Slide

65. View Slide

66. Slides:
    Code Used in this Talk:
    http://tompaulus.com/talks
    https://github.com/tpaulus/SCC-USC2013
    Email:
    tom@tompaulus.com
    

    View Slide