Raspberry Pi - Week 4

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Contents

Review

• Installed software with apt-get. (including festival).
• Installed and ran VNC to get a remote desktop on the machine.
• Ran a simple python script to synthesize speech ( example)
• Another python tutorial: Learn Python the Hard Way

Video Playback

• Omxplayer is a video player specifically made for the Raspberry PI's GPU made by Edgar (gimli) Hucek from the XBMC project.
  • omxplayer comes pre-installed on our raspbian distribution.
• Try it out.
• Copy a movie file to your raspberry pi using scp. The movie needs to be .mp4 format.
  • you can transcode with ffmpeg:
  • ffmpeg -i mouse_brain.wmv mouse_brain.mp4
• run omxplayer:
  • omxplayer ~/Movies/mouse_brain.mp4
• You can control playback with a number of hotkeys:
  • http://elinux.org/Omxplayer#Hotkeys
  • Try these, and notice the responsiveness of the system. Is there any noticable delay?

ffmpeg

• Install this on your computer, not the raspberry pi.
  • install homebrew
  • brew install ffmpeg
• using ffmpeg to transcode a video file:
  • ffmpeg -i ~/Movies/dogkiss.mov dogkiss.mp4

Scripting Video Playback

video_loop.tar

• We can send the hotkey controls via STDIN in python:
  • http://stackoverflow.com/questions/12755968/sending-arrow-keys-to-popen
• shell script to play a directory of files. (good at corporate conventions)
  • http://www.cenolan.com/2013/03/looping-video-playlist-omxplayer-raspberry-pi/

GPIO

• What are the pins?
  • http://elinux.org/RPi_Low-level_peripherals
• Handy printable reference
  • Raspberry Leaf - http://www.doctormonk.com/2013/02/raspberry-pi-and-breadboard-raspberry.html
• Other headers, not yet populated
  • P5, etc...

Note on voltage Levels

• RPi is 3.3V.
• pin over-voltage protection circuits - http://elinux.org/RPi_Tutorial_EGHS:GPIO_Protection_Circuits

Tutorials

• Single LED-https://projects.drogon.net/raspberry-pi/gpio-examples/tux-crossing/gpio-examples-1-a-single-led/
• GPIO examples-https://projects.drogon.net/raspberry-pi/gpio-examples/
• LCD interface https://projects.drogon.net/raspberry-pi/gpio-examples/lcd-interface/

using GPIO with python

• https://code.google.com/p/raspberry-gpio-python/
  • sudo apt-get update
  • sudo apt-get install python-dev
  • sudo apt-get install python-rpi.gpio
• Examples - https://code.google.com/p/raspberry-gpio-python/wiki/Examples
  • Basic Usage
  • Inputs
  • Outputs
  • PWM
• adafruit - http://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/overview