Getting Started with Raspberry Pi - UCSD 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
2. Recommended
3. Hardware
4. Model B
5. Model A
6. Raspberry
8. Arduino
9. 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
10. Initial Setup
11. http://www.raspberrypi.org/downloads
12. Recommended
13. 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: Use Raspberry PI SD Installer OS X
15. Demo
16. GPIO
18. sudo apt-get install python-dev python-pip sudo easy_install -U distribute sudo pip install RPi.GPIO Preparing
19. Simple
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
21. Hardware
22. Demo
23. Analogue
24. MCP3008 8-Channel 10-Bit ADC With SPI Interface Ra!berryPi wi" ADC
25. 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
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
27. I2C SPI
28. IN =[0000 0001][1CNL ----][---- ----] (8+channel) <<4 OUT=[---- ----][---- -XXX][XXXX XXXX] (10bit) ((r[1] & 3) << 8) + r[2]
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]
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
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
32. Hardware
33. But, That’s Just Ugly!
34. Let’s Add a Display
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 Ra!berryPi Inter-IC Bus - I2C
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
37. I2C SPI
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
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
40. MORE Inputs!!
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)
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
43. Hardware
44. Demo
45. Why? try: # Main Program except KeyboardInterrupt: # On Interrupt finally: GPIO.cleanup()
46. 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
47. Using
48. JSON
49. JavaScript
50. JSON
52. What
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
55. Displaying
56. Wea"er Client
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
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
59. USER Data!! NSA I have some data for you...
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()
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()
62. Demo
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
66. Slides: Code Used in this Talk: http://tompaulus.com/talks https://github.com/tpaulus/SCC-SD2013 Email: tom@tompaulus.com