This is my first RC car control by an Arduino and a wirless router running OpenWRT. There are many OpenWRT supported routers, I'm using a TP-Link TL-MR3020 3G/4G Wireless N Router for this project since it is very slim, low power consumption and it is cheap.

RC car features

• A webcam, the car can be driven without line of sight
• A horn so that you can honk at people.
• LED Headlights attached to the front of the car
• Two wheel drive motor
• Windows GUI application or web interface
• Future Additions: Control by a smartphone (Android & IOS)

Wheel Drive Layout

This project work with the following wheel drive layout.

Prerequisite

• If you do not have SSH client, you need to install one. I'm using PuTTY

• WinSCP (Windows Secure Copy)

• A Linux UVC supported cameras

• A router flashed with OpenWRT, please read here on how to flash the OpenWRT to a TP-Link TL-MR3020 wireless 3G/4G router

• Make sure the router have Internet connection (see below) as it will download the packages from OpenWRT repository

Setup Internet Connection for Router

Connect your PC to router as shown in figure below. After flasing OpenWRT to the router, make sure you have setup the internet connection.

 

Software

1. Arduino sketch runs on Arduino (Arduino_Wifi_Car folder)
2. Shell script (SH script) runs on the router (www folder)
3. The Delphi Wifi_car client application (Delphi Wifi Car folder) or the web interface (www folder) run on computer

 

Arduino Code

Upload the following sketch to Arduino

The serial data send from router to Arduino must start with a special character such as @ and follow by the command (eg. @2), the router may not work correctly (may cause delay) without the start character.

Shell Script run on Router

The Shell Script is just three lines of code, it act as the interface between router and Arduino. Name this file as "car" and save it to router /www/cgi-bin 

When a request is received by the server (router)  for CGI, the parameters it receives are through QUERY_STRING environment variable. QUERY_STRING retrieves the string that follows the ? delimiter in the URL for a query, an URL containing a query string is as follows:

http://routerIP/cgi-bin/[email protected]

When the server (router) receives a request for such a page (eg. http://192.168.0.1/cgi-bin/[email protected]), it will write the command (@2) to  /dev/ttyUSB0 port (it is COM1 in Ms Windows) 

Lua Script run on Router

Lua is come with OpenWRT. If you know Lua programming, you can use it to replace Shell Script.

GUI Interface

Besides the Web GUI, I wrote another client application which runs on MS Windows computer, you can compile the source code in Borland Delphi 7.

Interface between Arduino and Router

The router needs to install USB-SERIAL driver to work with Arduino, please select the correct serial driver for your Arduino.

• Run PuTTY and SSH ro router as shown in figure below

• Enter root as login and enter your router password as shown in figure below

• Update list of available packages and stores it on your router RAM partion (make sure your have internet connection
  

  opkg update

• If you are using Arduino Demilanove or FTDI usb-serial
  

  opkg install kmod-usb-serial-ftdi

• If you are using Teensy / Arduino Uno / Arduino Mega
  

  opkg install kmod-usb-acm

• If you are using PL2303 based USB/serial adapters
  

  opkg install kmod-usb-serial-pl2303

• If you are using CP201x based USB/serial adapters
  

  opkg install kmod-usb-serial-cp210x

Verify router is able to communicate with Arduino

Plug in Arduino to the router USB port and restart the router, wait until the router is ready then enter command below

Plug in the Arduino to the router via USB and use the HTTP GET method to control Arduino from browser.

Syntax: http://routerIP + /cgi-bin/car? + command 

Connect three LED to Arduino, first LED to D9, second LED to D10 and third LED to D6. Launch a browser and enter the URL as below:

Arduino PCB