getting started with raspberry pi - ucsd 2013

Getting Started with Raspberry Pi

Tom Paulus

www.tompaulus.com

@tompaulus

Recommended����������� ������������������  Books

Hardware

Model B

Model A

Raspberry����������� ������������������  Pi

Text

“Take����������� ������������������  a����������� ������������������  bite!”

CPUBroadcom ARM11

SoCBroadcom ARM11

SoC

ClockSpeed

Up to 1GHz ClockSpeed*

Up to 1GHz ClockSpeed*

Memory 256 MB 512 MB

USB 1 USB Port 2 USB Ports

Network None Onboard Ethernet

Model����������� ������������������  BModel����������� ������������������  A

Arduino����������� ������������������  UNO����������� ������������������  ����������� ������������������  :����������� ������������������  ����������� ������������������  Arduino����������� ������������������  MEGA����������� ������������������  ����������� ������������������  :����������� ������������������  ����������� ������������������  ����������� ������������������  Raspberry����������� ������������������  Pi����������� ������������������  

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/a10/100 wired Ethernet RJ45

n/a n/a n/aHDMI, 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 1612

2DAC Analog Out 0* 0*

$30 $59 $50 $25 $35

Initial Setup

http://www.raspberrypi.org/downloads

Recommended����������� ������������������  SD����������� ������������������  Cards

•Class����������� ������������������  4����������� ������������������  Minimum

•2����������� ������������������  GB����������� ������������������  or����������� ������������������  More

•Major����������� ������������������  Brands����������� ������������������  are����������� ������������������  Better!

Creating Your Image

1. Download and Unzip the .img from www.raspberrypi.com2. Format the SD Card to clear all Data

Windows Users:

UseWin32DiskImager

Mac Users:

UseRaspberry PI SD Installer OS X

Demo

GPIO

sudo apt-get install python-dev python-pipsudo easy_install -U distribute

sudo pip install RPi.GPIO

Preparing����������� ������������������  Python

Simple����������� ������������������  Blink����������� ������������������  App

from time import sleepimport 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 connecteddelay = .5GPIO.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����������� ������������������  Input

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-bcm2708blacklist 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-spidevcd 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) <<4OUT=[---- ----][---- -XXX][XXXX XXXX] (10bit)

((r[1] & 3) << 8) + r[2]

IN =[0000 0001][1CNL ----][---- ----]

(8+channel) <<4OUT=[---- ----][---- -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 timeimport spidevimport 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 = 0statusLED = 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 addressSDA - Serial DataSCL - 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-bcm2708blacklist 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 timeimport spidevimport RPi.GPIO as GPIOfrom lib.Char_Plate.Adafruit_CharLCDPlate import Adafruit_CharLCDPlateimport smbus GPIO.setwarnings(False)GPIO.setmode(GPIO.BCM)lcd = Adafruit_CharLCDPlate()spi = spidev.SpiDev()pot_adc = 0         # ADCl = list()          # List for Light Sensor AveragingstatusLED = 23print "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

Digital I/O Pins

Analog Input Pins

Price

40 mA

14 (6 PWM)

6

$30

Using����������� ������������������  Outside����������� ������������������  Data

JSON

JavaScript����������� ������������������  Object����������� ������������������  Notation???JSON

??{ "firstName": "John", "lastName": "Smith", "age": 25, "address": { "streetAddress": "21 2nd Street", "city": "New York", "state": "NY", "postalCode": 10021 }, "phoneNumber": [ { "type": "home", "number": "212 555-1234" }, { "type": "fax", "number": "646 555-4567" } ]}

JSON����������� ������������������  meet����������� ������������������  JASON

{ "firstName": "John", "lastName": "Smith", "age": 25, "address": { "streetAddress": "21 2nd Street", "city": "New York", "state": "NY", "postalCode": 10021 }, "phoneNumber": [ { "type": "home", "number": "212 555-1234" }, { "type": "fax", "number": "646 555-4567" } ]}

What����������� ������������������  time����������� ������������������  is����������� ������������������  it����������� ������������������  in����������� ������������������  <city>?

#! /usr/bin/python#Written By Tom Paulus, @tompaulus, www.tompaulus.com import requestsimport 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

Displaying����������� ������������������  the����������� ������������������  Data

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!')

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.pyapp_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

SummaryWow! We have learned a lot!!

1. Initial Setup of the Raspberry Pi2. Made a little LED blink

3. Dealt with an Analog Value and Displayed it4. 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

Slides:

Code Used in this Talk:

http://tompaulus.com/talks

https://github.com/tpaulus/SCC-SD2013

Email:

tom@tompaulus.com