8. Creating a Raspberry Pi Line-following Robot | Raspberry Pi Essentials

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Raspberry Pi Essentials

By : Jack Creasey

3.8 (5)

Raspberry Pi Essentials

3.8 (5)

By: Jack Creasey

Overview of this book

Programmers new to the Raspberry Pi and novice programmers with little to no experience with micro board computing will find the book useful. A basic knowledge of programming languages in general will prove useful for a better understanding of the topics.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Getting Started with Raspberry Pi

1. Getting Started with Raspberry Pi

Let's get started

Unboxing the Raspberry Pi

Local display, keyboard, mouse, or remote headless access

Selecting a screen

Getting your SD Card ready

Booting the Raspberry Pi for the first time

A quick tour of the desktop

Instructions for downloading all project files

Summary

2. Configuring the Raspberry Pi Desktop and Software

2. Configuring the Raspberry Pi Desktop and Software

Hardware and software networking configuration

Configuring the Raspberry Pi desktop and software

Desktop and file manager accelerators

Project 1 – Building a talking clock with a Bash script

Building a talking clock with Python 3

Summary

3. Raspberry Pi and Cameras

3. Raspberry Pi and Cameras

Connecting cameras to the Raspberry Pi

PiCam and PiNoIR

Webcams

Project architecture for the Raspberry Pi security camera

Features and limitations of the cameras

Project 1 – Running raspivid as a background service

Project 1a – Creating a Bash script to drive raspivid

Project 1b – Creating a movement detector with a USB camera

Project 2 – Combining the webcam movement detector and the PiCam camera

Project 3 – Creating a simple Python GUI for the security application

Summary

4. Raspberry Pi Audio Input and Output

4. Raspberry Pi Audio Input and Output

Audio quality and bandwidth

Audio capability on the Raspberry Pi

Understanding the ALSA configuration

Configuring the Raspberry Pi to support high-quality sound

Project 1 – Installing an advanced audio playback application

Building an Internet radio based on VLC and Raspberry Pi

Project 2a – Running VLC in the background for the Internet radio

Project 2b – Designing a playlist file for the Internet radio

Project 2c – Parsing the playlist file for the Internet radio

Project 2d – Implementing a Python text interface to VLC

Project 3 – Implementing a TKinter GUI for the Internet radio

Recording sound files on the Pi

Summary

5. Port Input and Output on the Raspberry Pi

5. Port Input and Output on the Raspberry Pi

Understanding Raspberry Pi digital input and output ports

Driving LEDs as output indicators

TKinter LED demo

TKinter switch demo

Adding a physical switch interface to the Internet radio

Project 1 – Add a switch interface to the Internet radio

Summary

6. Driving I2C Peripherals on the Raspberry Pi

6. Driving I2C Peripherals on the Raspberry Pi

Getting started with I2C

Project 1 – Python control of a PWM board driving RC servo motors

Summary

7. Going Mobile with Raspberry Pi

7. Going Mobile with Raspberry Pi

Remote access to the Raspberry Pi

Remote access from Linux and OSX

Testing your remote session from a PC or Mac

Battery power systems

Project 1 – Selecting a project battery capacity

Summary

8. Creating a Raspberry Pi Line-following Robot

8. Creating a Raspberry Pi Line-following Robot

Implementing a line-following robot

Line-following robot architecture

Implementing rbuttons.py

Implementing rwheel.py

Implementing navigate.py

Steering algorithm

Time to build the mobile system

Line-following robot

Summary

Index

Index

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Implementing navigate.py

The final module for our line-following robot is navigate.py. This program initiates the pipes that will instantiate the rbuttons.py, rcam.py, and rwheel.py programs as separate processes using multiple Popen() functions. It provides a minimal user-text-mode interface, provides the logic to handle button functions, and most importantly provides the logic to steer the robot.

Downloading navigate.py

The following shows the steps to download navigate.py as well as the explanation of the code's functionality:

Use the command line to open a new instance of the Python 2 IDLE (it does not need to have root privilege).
Download navigate.py from the Chapter 8 folder at http://1drv.ms/1ysAxkl
Open navigate.py in the Python IDE (non-privileged).

Review the main() function as follows:

def main():
    if startpipes():
        print 'Aborting....something did not start!'
        sys.exit('Closing application')
    #Start scanning loop
    while True :
        try:
            start...

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