Personally, I find this to be a sad state of affairs when an intelligent robot with SONAR vision is asked to behave like an RC car.   I’ve named this mode of operation “Slave Mode” to quietly voice my opinion on the matter.  It’s something like a zombie version of the same rover and you can understand why R2-D2 was so interested in getting rid of that restraining bolt in the first Star Wars movie so he could run for the hills.

For the record, I wrote a command interpreter for the Rover so you can send him into Slave mode with a Wi-Fi device, ZigBee, or even from his own web server.  Truly, he is not going to escape and run off to find Obi-Won Kenobi.

Adding ZigBee to the Rover… Scary Scary!

I admit that ZigBee is pretty intimidating but getting him up and running was less than a day with the Rabbit code.

The first thing you want to realize is that you can set up one of the ZigBee modems to fake out a serial port.  Why is that important?  It means my Rover doesn’t need to know “thing one” about ZigBee.  He just writes or reads with his serial port and the modem does all the work.  If there is no need to worry about the ZigBee software, I don’t increase my project’s code size and my CPU doesn’t have to carry the overhead either.

On the other end I have an RCM4510W acting as the ZigBee coordinator to the Rover’s ZigBee end device.  He comes up using our ZigBee API, sends off a command to set the Rover’s modem as a transparent serial port and then sits there listening as my rover happily chatters away to his fake serial port.  Little does he know that every log entry is being passed wirelessly to my other Rabbit where I can easily dump the data into a log file.

ZigBee at Play

In this video you can see our Rover happily face-planting into a cube wall while he reliably sends us a description of his many woes via the ZigBee connection back to my PC.

You will see an XBee Series 2 modem on the Rover in the video and in the image below.

You can see the blue ZigBee Modem on the PCB.

Test # 29 – SONAR Sweeping Bench Test

Test #30 – SONAR Sweeping Floor Test

Here we are getting closer to good collision avoidance.  Bob the Dreaded Conduit Pipe looks like he may be close to defeat.

Test #27 – Oops!

Here the Rover is crashing because we aren’t sending any braking to his motors.  That means he is coasting forward even when he detects an obstacle.

Test #28 – Restoring the Hard Braking

Here the braking has been restored.  We brake by sending 1-2 inverted pulses to the motors which pops the wheels in the opposite direction very briefly.  It’s a jolting stop, but it certainly beats crashing.