Getting Pleo to make purposeful movements and sounds starts with processing all of the input he receives. The eight touch sensors are a big source of information. Sosoka explains, "Each of [the touch sensors] has dedicated processing that they can do inside of a dedicated chip."
A separate processor in Pleo's head handles input from the area around that part of his body. Sosoka describes the processing power located there:
It's an ARM7 32-bit microprocessor, and it's very powerful and it's very fast ... That processor is responsible for managing the sound input through Pleo's two microphones for binaural hearing. [It also handles] infrared communication and infrared object detection and for the CMOS sensor, the camera sensing ... there is a photo interrupter in his mouth, so when we put something in its mouth ... that's opaque [to infrared light] Pleo can sense that it's there. That processor also manages the two touch sensors that are right there under his chin and on top of his head. Pleo's Head Pleo's slightly oversized head isn't just for the sake of appearance. In addition to all the sensors and processing power stored there, the head contains a motor and a gearbox to control his eyes and mouth.
Other processors help turn all this input into movement. Sosoka explains:
There are four small, 8-bit microprocessors, and those ... are used to control the motors. So they take the high-level motion description, kind of like a vector format for motion, and then they render it into the actual motion that Pleo has. They do that through the use of a servo motor system ... they do a few other housekeeping chores, but they are primarily running the 14 motors.
Pleo's final microprocessor, another ARM7 23-bit processor, governs Pleo's connections to computer data from the outside world. "It handles the SD card, it handles the USB, it manages the flash data," Sosoka says. This processor also acts as Pleo's overall brain. "It manages the talking to the head, talking to the motor controllers, it deals with kind of all the other stuff that's going on in there. That's where Pleo's personality and behavior exist."
On the next page, we'll look at how Pleo's body carries out these instructions, and we'll explore some of the challenges the development team discovered when working on Pleo's physical structure.