Nuts and Volts - May 2013

THE DESIGN CYCLE

■ BY FRED EADY

ADVANCED TECHNIQUES FOR DESIGN ENGINEERS CONTROLLING HOMEBREWED DEVICES WITH A PS DUALSHOCK 3

There are some things in life that must be done. This project is one of them. How can any red-blooded geek or nerd resist the siren song emanating from the multitude of buttons and joysticks that reside on the island of PlayStation DualShock 3? This month, we will begin an odyssey that will take us to the villages, towns, and cities of a province called USB, which resides in the land of PlayStation. We will travel on a Microchip PIC32MX fueled by the Microchip Application Libraries' free USB stack. Along the way, funds for our travels will be provided by Ellisys and the Microchip X series of C compilers and IDEs. By the time we arrive at our destination, you will be an experienced USB traveler. In addition, you will have also mastered the USB ways of the PlayStation DualShock 3 controller.

THE PLAYSTATION DUALSHOCK 3

There isn’t much I can tell you about the physical PlayStation DualShock 3 that you don’t already know. Besides, we humans are already programmed to push buttons and wiggle joysticks. In that we want to manipulate the PlayStation DualShock 3 with USB bits of our choosing, we’ll take a look at what is going on inside of the DualShock 3.

The best way to get the skinny on the DualShock 3 USB speak is to smell the PlayStation 3’s cooking. Our DualShock 3 USB sniffer is the Ellisys USB Explorer 200 you see standing on its four rubber feet in

Photo 1. I used my laptop and a free program called MotioninJoy to awaken the DualShock 3. The USB Explorer 200 captures the DualShock 3 USB data stream by sitting between the MotioninJoy application and the PS3’s USB interface. A typical Explorer 200 USB session capture can be seen in Screenshot 1.

To get a good idea about what we need to code to connect with the DualShock 3, we’ll use the Explorer 200 to sniff out the PS3’s USB descriptors. The Microchip USB stack automagically retrieves the PS3 descriptors at enumeration time.

A quick look at Screenshot 2 tells us that the PS3 is bus powered and would like to use the maximum

■ PHOTO 1. Other than capturing every little nuance of a USB data stream, I am able to use the Ellisys USB Explorer to record those data streams for further analysis. All you have to do is load and run a copy of the free Ellisys Visual USB application to view my recorded USB data stream captures with your PC.