Introduction

"Our 3D gForce Mouse will enable use to move the curser in the air freely with the capacity of scrolling"

The rationale for this design is two fold. We wanted to do this design because we wanted to make a zero-impact pointing device for those with injury. We also wanted to implement this injury conscious device for its business opportunities.

We are using the 2-axis ADXL202 accelerometer to measure acclecration and tilt to operate the mouse. We measure the analog output signal and perform A/D conversion on the Mega32 MCU and the STK500 protoboard. Then the MCU generates serial signal packets on STK500 output pins to drive the computer mouse according to the PS/2 standard protocal. This mouse will perform horizontal and vertical movements in addition to scrolling. We will simulate clicking of the mouse buttons by having push buttons on our design breadboard. We origionally designed mouse to calcuate displacement in space due to 3-D acceleration. However we found out that the accelerometer is more accurate in measuring tilt than measuring short pulses of movement. Also, we had to work with the PS/2 protocal because we wanted to implement the scrolling function with our mouse.

Making the PS/2 protocal function is the biggest challenge of our project. The PS/2 protocal is a two way serial transmittion protocal, where the computer (or host) can request to send information to the device. There are no "official" documentation on the PS/2 protocal, but there is execellent information on http://govschl.ndsu.nodak.edu/~achapwes/PICmicro/