ADNK-3043-TI27 データシートの表示（PDF） - Avago Technologies

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ADNK-3043-TI27

Wireless USB Optical Mouse Designer’s Kit

Avago Technologies 

Z Wheel

The motion of Z-wheel is detected using the quadrature

signal generated by optical sensors. Two phototransistors

are connected in a source-follower configuration forming

Channel A and Channel B . An infrared LED shines, causing

the phototransistors to turn on. In between the phototran-

sistors and the LED is a pinwheel that rotates. The spokes

of this pinwheel is mechanically designed to interrupt the

infrared light such that the phototransistors are turned on

and off in a quadrature output pattern. Every change in

the phototransistor outputs represents a count of Z-wheel

movement. Comparing the last state of the optics to the

current state derives directional information. As shown

in Figure 3 below, rotating the wheel forward produces

a unique set of state transitions, and rotating the wheel

backward produces another set of unique state transi-

tions.

Hardware Implementation

Optical Mouse Sensor

This reference design features the ADNS-3040 optical

navigation engine. It contains an Image Acquisition System

(IAS), a Digital Signal Processor (DSP), and a four-wire Serial

Peripheral Interface consists of the serial clock (SCLK), the

master-in/slave-out (MISO) and the master-out/slave-in

(MOSI). In addition a fourth signal chip select (NCS) is used

to select the device on the SPI buss. Motion, is an addi-

tional output from the ADNS-3040 intended to act as an

interrupt to the microcontroller whenever the ADNS-3040

senses motion. When the mouse is moved the ADNS-3040

alerts the system controller by activating the Motion signal

triggering an interrupt service routine. At the same time

the ADNS-3040 accumulates the horizontal and vertical

displacements (count per inch, or cpi) in its Delta_X and

Delta_Y registers respectively. The ADNS-3040 deactivates

the Motion signal as soon as movement stops. The Smart-

Speed technology automatically optimizes the frame rate

by examining the acquired images of the surface. It also

manages the integrated LED driver to coordinate with the

shutter.

The system controller reads the motion information and

reports it to the PC to update the cursor position.

The advantages of using ADNS-3040 optical sensor are the

efficient power management, high tracking accuracy, and

simple communications with the microcontroller via the

full duplex SPI port.

To learn more about sensor’s technical information, please visit the

Avago web site at http://www.avagotech.com

Figure 3. Optics Quadrature Signal Generation

Mouse Buttons

Mouse buttons are connected as standard switches. These

switches are pulled up by the pull up resistors inside the

microcontroller. When the user presses a button, the switch

will be closed and the pin will be pulled LOW to GND. A

LOW state at the pin is interpreted as the button being

pressed. A HIGH state is interpreted as the button has been

released or the button is not being pressed. Normally the

switches are debounced in firmware for 15-20ms. In this

reference design there are three switches: left, Z-wheel,

and right.



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