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ISSUE 10 MAR 2013

Get printed copies at

themagpi.com

A Magazine for Raspberry Pi Users

This Issue...

WebIOPi Framework

Expansion boards

Backup SD cards

Scratch fractals

BASH basics

Charm

Win a 512Mb

Model B

Raspberry Pi

& case!

Raspberry Pi is a trademark of The Raspberry Pi Foundation.

This magazine was created using a Raspberry Pi computer.

www.

hemagpi

com

h p www hemagp com

Welcome to isssue 10,

Thank you to all of those who have ordered volume one (issues 1-8). After

some printing delays, the cordex binder for volume 1 has been submitted for

rapid production. The final pdf files needed for printing each of the magazines

are nearing completion. We expect to be releasing pdfs for printing this week.

We are very grateful for your continued patience. Such delays are not expected

with volume 2, since all of the articles are already in the correct format for

printing.

In this month's issue there is a great selection of hardware and software

projects. We are pleased to present part 2 of the WebIOPi and backup articles,

new programming langauges and our regular Scratch and Python pages. For

those looking for automation solutions, there is one article with a whole range

of extension boards.

We are on the look out for willing volunteers to help with layout, testing and

proof reading activities.

If you can dedicate some time, please email

editor@themagpi.com.

Chief Editor of The MagPi

The MagPi Team

Ash Stone

- Chief Editor / Administration

Chris 'tzj' Stagg

- Administration

Matt '0ther0judge0'

- Website / Administration

Tim 'meltwater' Cox

- Administration

Lix

- Administration

Aaron Shaw

- Page Design / Graphics

Bryan Butler

- Page Design & Theme / Graphics

Ian McAlpine

- Page Design / Graphics

Isa McKenty

- Page Design

Simon Johnson

- Page Design

Steve Drew

- Page Design

W.H. Bell

- Page Design / Administration

Mark Robson

- Proof Reading

Michael Beaucage

- Graphics

Contents

CAM - PART 2

REMOTE CONTROLLED ROBOT

REST Framework (WebIOPi)

Robot remote control with raspberry Pi

COCKTAIL OF EXPANSION BOARDS

selection of different expansion boards for interfacing projects

MONTH'S

1 1

THIS

512mb Rasp.

COMPETITION

from PC Supplies LTD

Win a

Pi model B and case,

- PART 2

1 2

BACKING UP

card images safe and restoring backups

Keeping the SD

GAFFER

1 6

BASH

some lashup

TAPE

with the Bourne-again shell

Learn

scripts

1 9

WHAT'S ON GUIDE

in your area

Find this month's events

TO CHARM

INTRODUCTION

to get coding with the Raspberry Pi

Encouraging others

C++ CACHE

streams, reading and writing files

Introducing C++

PART

SCRATCH PATCH - GPIO CONTROL

Pi with a

Celebrate the anniversary of the Raspberry

LEDborg candle

SCRATCH FRACTALS

Scratch

Generate fractal images with

PYTHON PIT

client-server model for parallel calculations

Using a simple

FEEDBACK FROM READERS

HAPPY BIRTHDAY RASPBERRY PI!

http://www.themagpi.com

WebIOPi - Raspberry Pi REST framework

Remote Controlled

Robot Cam, Part II

DIFFICULTY : ADVANCED

Building the interface

Building your own interface is also easy, and is

based on a HTML file embedding some

Javascript. You only have to load the webiopi.js

file from your HTML file to use the WebIOPi

power. Create a new index.html file next to your

Python script:

<html >

<head>

<ti tl e>CamBot</ti tl e>

<scri pt type=" text/j avascri pt"

src=" /webi opi . j s" ></scri pt>

// J avascri pt code goes here

</scri pt>

</head>

<body>

</di v>

</body>

</html >

Eric PTAK

Guest Writer

In the script section, we add an init function to

build the interface using WebIOPi library. It

contains many functions to ease creation of

buttons that control GPIO. Here we use a basic

button to call a different function on press and

release. Each function calls a different macro on

the server. Don’t forget to register the init

function to WebIOPi. It will be called when

everything is loaded and ready.

functi on i ni t() {

var button =

webi opi (). createButton(

" bt_up" ,

// i d

" /\\" ,

// l abel

go_forward, // press

stop);

// rel ease

$(" #box" ). append(button);

}

functi on go_forward() {

w(). cal l Macro(" go_forward" );

}

functi on stop() {

w(). cal l Macro(" stop" );

}

webi opi (). ready(i ni t);

Take note of the starting slash when loading

webiopi.js, to ensure it will be searched in the

root of the server or it may be not found.

I added an empty script section; we will use the

WebIOPi JS library here. There is also a div box,

which will contain controls.

Be careful that webiopi() is a function and a

reserved word that need brackets to return the

WebIOPi object. You can use w() to short the

webiopi() call.

It’s now time to start the server and enjoy the

interface. Open a terminal in the folder you

created Python and HTML files and execute the

script:

$ sudo python yourscri pt. py

Resetti ng camera setti ngs

Camera bri ghtness l evel i s 0

Camera contrast l evel i s 255

Camera saturati on l evel i s 255

Camera gai n l evel i s 255

Savi ng i mage to: snap. j pg

If uvccapture returns without error, we can

continue to stream the webcam.

I use MJPG-STREAMER, which is really easy to

use. It gives me a 320x240@25fps pass-through

MJPEG stream over HTTP. I tried FFMPEG but

it takes the RAW output of the webcam to

encode it in MJPEG with a framerate under 5fps.

You can download MJPG-STREAMER at

http://sourceforge.net/projects/mjpg-streamer/

You will also need libjpeg8-dev you can install

using aptitude/apt-get.

Uncompress and build MJPG-STREAMER using

make command. Then execute it:

$ . /mj pg_streamer - i " . /i nput_uvc. so

–r 320x240 –f 25" - o " . /output_http. so

–n –p 8001" &

Open a browser to the webiopi to control the

chassis. Hold the button to go forward and

release it to stop. The last piece missing is the

webcam.

Add a webcam stream

There are many possibilities to stream a

webcam, which may depend on the model you

have. In my case, I have a recent webcam which

outputs both RAW and MJPEG formats up to

1280x720@30fps.

First, check your webcam is installed with a

terminal:

$ l susb

[. . . ]

Bus 001 Devi ce 005: ID 046d: 0825

Logi tech, Inc. Webcam C270

$ l s /dev/vi deo*

/dev/vi deo0

Back to HTML file, add a img tag with src set to

http://raspberrypi:8001/?action=stream replacing

raspberrypi by your Pi’s IP. You can also directly

try the URL in your browser.

...

<i mg

src=" http: //raspberrypi : 8001/?acti on=s

tream" >

</body>

</html >

Then, to check it’s working, you can install

uvccapture using apt-get or aptitude and take a

single snapshot:

$ uvccapture - v

Usi ng vi deodevi ce: /dev/vi deo0

Savi ng i mages to: snap. j pg

Image si ze: 320x240

Taki ng snapshot every 0 seconds

Taki ng i mages usi ng mmap

Conclusion

With this article, you learned how to install

WebIOPi and how to use it in your own Python

scripts to write macros you can call from the web.

Plik z chomika:

Leniek

Inne pliki z tego folderu:

Inne foldery tego chomika:

humble_bundle