Nuts and Volts

THE DESIGN CYCLE

■ BY FRED EADY

ADVANCED TECHNIQUES FOR DESIGN ENGINEERS TAMING THE DUALSHOCK 3 BEAST

The PlayStation DualShock 3 was initially designed as a user interface for the PlayStation gaming system. Fortunately for us, Sony decided to design the DualShock 3 around the USB HID specification.

HID devices do not normally require any specialized operating system-dependent drivers.

Using the HID specification potentially allows the DualShock 3 to connect to most any USB host device. This works to our advantage. The Microchip USB stack supports standard HID protocols hosted by PIC32MX microcontrollers.

All we have to do is determine what the DualShock 3 wants to hear, and get the messages through via a HID-based USB link.

SNAKES AND PENGUINS

Despite the snake problem we are now enduring in the Florida Everglades, uttering the word Python is not all bad. The “bad” pythons are quickly gobbling up our four-legged critters (alligators included). The “good” pythons aren’t really snakes at all. These “Pythons” that don’t coil and swallow deer whole represent a programming language.

Unlike leopard seals, sharks, and killer whales, Python (the programming language) does not prey on penguins. The penguin described here doesn’t slide on ice and eat cold fish. The penguin represents the operating system we call Linux.

In that our “animals” are really units of logic, we could logically state that, in this case, the snake talks to the penguin. We could also look at it from the reverse perspective and state that the penguin eats the snake. (Let’s not go there.) To give us some clues as to how to code our PIC32MX USB host, we must listen to the snake too. For instance, this hissing will come in handy later:

const unsigned char
enable_SIXAXIS[] =
{0x03,0xF4,0x42,0x0C,0x00,0x00}
;

As we work our way through the PIC32MX PlayStation DualShock 3 client driver code, we will depend heavily on the snakes in the grass. We’ll also use all of the hardware technology and applications available to us to fill in the bits and bytes of information that the snakes and penguins won’t share with us. The Ellisys USB Explorer 200 and MotioninJoy Gamepad Tool will be very busy.

■ SCREENSHOT 1. It is very important to know the device address that gets assigned to the PlayStation DualShock 3. The Microchip USB stack takes care of the device addressing task automagically.