This document discusses building a remote controlled car using a Raspberry Pi. The car uses WiFi to connect to a smartphone app for control. The software runs on Java and Node.js and integrates services like Redis. Hardware challenges included modifying an ultrasonic sensor for the Raspberry Pi and reusing parts from a toy car. Lessons learned focused on automation, testing, and prototyping. Future projects discussed using a Raspberry Pi for a quadcopter or tank.

1. RASPBERRY PI CAR
BOGDAN CRACIUN
SIVECO ROMANIA
Build, Code, Deploy and Run

2. Agenda
 Introduction
 Requirements
 Hardware platform
 Software platform & Application code
 Q&A
 Running Mode Demo

3. About me
 Software Architect @ SIVECO Romania from 2003
 Oracle Certified Master, Java EE Enterprise Architect
 Founding member of Oracle Architects Club – Romania chapter

4. Requirements
 Wireless control - no wires
 Wi-Fi based
 Smartphone and Car only setup
 No external Wi-Fi access point needed
 No additional administration system
 Automatic startup of services on power on
 Queue base control
 Automatic impact detection and reaction
 Front lights control
 Status lights for Impact Mode and Commands

5. Main actor

6. Secondary roles

7. Prop

8. Victim

9. Result
v1 v2

10. Running environment

11. Development environment

12. Operating system setup
 Operating system
 Rasbian “Wheezy” – Debian based Raspberry Pi distribution
 Access point
 Hostapd
 EW-7811Un with custom drivers to support AP mode
 DNS & DHCP
 Dnsmasq
 Remove serial console support from standard Raspbian distribution

13. Service integration
 Java Application
 Java Service Wrapper
 Node Application
 Nodejitsu Forever
 Linux native program
 Scripting

14. JeeNode integration
 Using serial communication
 RXTX Java library with native support

15. Car engine
 Java SE Application
 Spring Framework
 IoC container
 Spring Integration
 Redis Channel Adapter
 Custom Serial Channel Adapter
 Using RXTX Serial library

16. Control component - Client
 Client
 JQuery Mobile
 User interface and
interactions
 Socket.io
 Client <> Server
communication
 Virtualjoystick.js
 Dual virtual joystick
support

17. Control component - Server
 Server
 Node.js Server
 Server components (request
handlers and queue
management)
 Redis Server
 Node <> Java integration
using Redis Pub/Sub
 Queue persistence using
Redis sorted sets

18. Image streaming
 mjpg-streamer
 With Raspberry Pi Camera support – 11 fps @ 640x480

19. Software challenges
 No AP mode support in EW-7811Un
 Action: Custom hostapd compatible RTL8188CUS was installed
 Reading HC-SR04 sensor data using Java
 Works fine if it is the only process on Raspberry Pi
 Bad choice to use the sensor with a non real-time SO
 Action: Added a Jeenode (Arduino Uno clone) to run the reading
loop and push data to a serial Raspberry Pi port

20. Software challenges – cont.
 Compiling the following on Raspberry Pi:
 redis server
 node.js
 RXTX native library
 mjpg-streamer – custom module to support image streaming
 Image streaming speed optimization

21. Hardware challenges
 Differences between Raspberry Pi and HC-SR04
Ultrasonic Sensor - 3.3v vs 5v
 Action: Used a basic voltage divider between the
Echo port and the GPIO pin of the Raspberry Pi
 Reuse the dual H-bridge from the toy car PCB
(Printed Circuit Board) or integrate the L298N board
 v1 reuse car PCB
 v2 is connected to motors using L298N board

22. High level Architecture

23. Detailed Diagram

24. Detailed Diagram

25. Lessons learned
 Automate as much as possible
 Build automation
 Test automation
 Use mocks for development and testing
 Development without the real car
 Design a component based system for easy refactoring
 Switch between implementations easy
 Prototype before develop
 It is harder to change something already developed and fully
integrated
 Switch log levels to error/fatal/off
 Use versioning and release management for code and hardware
designs
 Don’t use / break children toys !

26. Final thoughts
 Be a problem solver, not just a programmer.
 Use the best tool for the job
 Does the language really matter?
 Keep your mind open.

27. Testing Team

28. Next projects
 Raspberry Pi assisted
quad-copter
 Raspberry Pi controlled
Tank

29. Q&A
 Demo car connection data:
 SID: orange
 Password: 12345678