getting started with raspberry pi - usc 2013
DESCRIPTION
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
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
Clock Speed
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 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/a10/100 wired Ethernet RJ45
Audio / Video n/a n/a n/aHDMI, 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����������� ������������������ SD����������� ������������������ Cards
•Class����������� ������������������ 4����������� ������������������ Minimum����������� ������������������
•2����������� ������������������ GB����������� ������������������ or����������� ������������������ More����������� ������������������
•Major����������� ������������������ Brands����������� ������������������ are����������� ������������������ Better!
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
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 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����������� ������������������ Input
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����������� ������������������ 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 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
Displaying����������� ������������������ the����������� ������������������ Data
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.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-USC2013
Email: