Servo - August 2015

I have been talking about adding vision to robots these last two columns and I will continue with that theme this month. There are many camera options to choose from that are small enough to fit on just about any robot. The simple camera modules often output their data in ways that our lower cost controllers cannot handle. Some output analog levels need to be converted on a pixel-by-pixel basis, and we need to track horizontal and vertical sync signals. Some output digital values for each pixel, but use a compressed video format that our microcontrollers lack the processing power (or memory space) to deal with.

With that in mind, I went searching for cameras that could be interfaced to our simple microcontrollers that can be used with rudimentary vision algorithms to do either navigation or object detection.

The Gameboy Camera Hack

When we consider using inexpensive vision systems with our inexpensive robot controllers, we should mention the first hacks which made this possibility a reality over 10 years ago. I speak, of course, about the Gameboy® camera hacks that were able to give small robots monochrome vision. The first hack that I know about is detailed in the SRS Encoder (Seattle Robotics Society Newsletter) in 2002 ( www.seattlerobotics.org/encoder/200205/gbcam.html).

The article was by Dafydd Walters and used a 68332 robot board. The link will give you the details of how he used the camera.

The second source I know personally. Daniel Harrington showed me his Gameboy camera hack in action. Daniel used a custom controller board with an Atmel 8515 that he demonstrated following a white ping-pong ball. A write-up of his design is actually on the Atmel microcontroller site.

I tried to include the direct link here, but the URL is really ugly. So, I suggest that you go to www.atmel.com and search for “issue4_pg39_ 43_ robotics.pdf” to get Daniel’s project. Figure 1 is a picture of his ping-pong ball tracking robot. His article can also be found in Circuit Cellar issue #151

(February 2003); you can find his code files at www.dtweed.com/circuitcellar

/ caj00151.htm.

This camera is particularly interesting because it had edge-detection features that simplified using it for object tracking. Because it is monochrome, you can pull an image from it with our newer, faster microcontroller boards very quickly to analyze images in real time.

If you like hacking your own stuff, I recommend that you check these articles out and try it yourself. You can still get these cameras on eBay for $7 or so. The total cost of this project will be time and probably less than $10 in parts (not including the microcontroller board).

by Dennis Clark

Our resident expert on all things robotic is merely an email away.

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r. Roboto is limping back from crawlspace floodwaters this month. The "mile high" land of Colorado seems more like a mile deep these days. My spirits are high, however, and I have nearly beaten the kelpies back from taking over the house. Things should be settling down soon! As I write this column, the SparkFun 7th annual AVC competition is coming up in a week. You can bet Mr. Roboto will be there to cheer everyone on and watch for innovations that we can all pick up on! Anyway, let’s move onward to this month's topic: robot vision.