2

Left Button

ADNS-6000

Optical Mouse Sensor

Wheel Button

Right Button

Z Optics

Sunplus SPCP825A

USB Controller

USB interface

MISO

MOSI

SCLK

NCS

D+/D-

SCLK/SDATA

VREG

1.3k Ohm

Avago Technologies

Firmware Configurable GPIO

The reference firmware is configured to use the GPIO pins

as shown on the schematic in Appendix A. However, it

may be more optimal to use a different I/O configuration

to meet the mechanical constraints of PCB design. The

reference firmware is designed to be easily configured

to another set of pin connections. This is accomplished

through changes in the I/O definitions at the beginning

of the SPCP825A_A6000.asm listing. The following state-

ments are the pin definitions as they exist today. The

firmware will use these definitions to read and configure

the GPIO pins, without any other modifications.

Communications between the Sunplus SPCP825A and

the ADNS-6000 are done through the integrated SPI

interface. The serial port cannot be activated while the

chip is in power down mode (NPD low) or reset (RESET

high). When the SPI is enabled thru PB0 (NCS), the PB2

(SCLK), PB1 (MISO) and PB3 (MOSI) GPIO pins serve

special functions to enable the SPI interface to talk with

external hardware. During normal operation, the Sunplus

SPCP825A SPI is always configured as a Master to output

the serial clock on PB7. Therefore, the USB microcontroller

always initiates communication. Data sent by the ADNS-

6000 optical sensor is received on the PB1 (MISO), and

data is shifted out to the ADNS-6000 through the PB3

(MOSI). See the schematic in Appendix A. When writing

to the ADNS-6000, the microcontroller drive both the

SCLK and the MOSI lines. When reading from the ADNS-

6000, the microcontroller drives both the SCLK and MOSI

Figure 1. Sunplus SPCP825A - ADNS-6000 Optical Mouse Hardware Block Diagram

Hardware Implementation

The standard hardware to implement a mouse is shown

in Figure 1. For X and Y movement, the optical sensor

is used. The Z- wheel movement is detected by a set of

optical sensors that output quadrature signals. For each

button there is a switch that is pulled up internally by the

built in pull up resistors. The D - line is pulled up via a 1.3k

ohm resistor connected to the VREG pin.