An Interface between the Arduino and the Vexplorer

I picked up a vexplorer from woot! recently with the goal of using my arduinos with it. The vexplorer has a wireless color camera as well as a gripper. The vexplorer is designed to be more like a remote control toy than a autonomous robot and if I had any chance of using my arduinos with it it would be good to have a flexible interface to the unit.

There are several internet resources that describe how to take the vexplorer hardware and interface it with alternate forms of control. Basically, there are two options 1) interface using pulse position modulation (PPM) signals or 2) discard the radio transmitter and receivers and interface directly to the motors of the vexplorer using H bridges.

Here are a few links describing a PPM interface:

• http://profmason.com/?p=513
• http://www.vexforum.com/showthread.php?t=7056&page=2

Here is a link to using H bridges - http://www.instructables.com/id/How-to-Program-the-Vexplorer-Using-Arduino/ and an Arduino shield that provides motor control http://www.adafruit.com/index.php?main_page=product_info&cPath=17_21&products_id=81

I wanted to be able to control the vexplorer wirelessly using an arduino and do so in a low cost way. Specifically, I wanted the arduino to receive input from the joysticks and buttons of the radio transmitter, send motor commands to the vexplorer, receive commands from the radio transmitter and finally control the motors of the vexplorer. Thus I opted for a two way PPM interface at both the transmitter and receiver. This should allow for several cool projects including:

• translation of a single joystick's X/Y position such that it controls both drive motors of the vexplorer i.e., use a single joystick to control the vexplorer's movements instead of two joysticks in tank control mode. I should be able to locate the arduino at the transmitter or the receiver
  
• image processing on my computer with feedback to the vexplorer as described at profmason.com
  
• movement macros
  
• autonomous behaviors but still have the option of radio control to override the robot