3
Figure 2. Optics Quadrature Signal Generation
Optical Sensor
Avago Technologies ADNS-6000 optical sensor is used in
this reference design as the primary navigation engine.
This Optical Navigation Technology contains an Image Ac-
quisition System, a Digital Signal Processor, a two channel
quadrature output, and a four-wire serial port. The
Sunplus SPCP825A periodically reads the ADNS-6000’s
Delta_X and Delta_Y registers to obtain any horizontal
and vertical motion information happening as a result of
the mouse being moved. The output of the ADNS-6000
optical sensor is 4-wire serial port.
This motion information will be reported to the PC to
update the position of the cursor. The advantages of using
ADNS-6000 optical sensor are the best tracking accuracy,
fl exibility of programming the optical sensor via the SPI
port, and the automatic frame rate feature (1000fps to
6400fps). Besides, ADNS-6000 optical sensor performs
excellent tracking on diffi
cult surfaces which convention-
al Led based technology is unable to track such as glossy
and smooth surfaces. In addition, Burst mode is another
special serial port operation mode that may be used to
reduce the serial transaction time for three predefi ned
operations: motion read and SROM download and frame
capture. The speed improvement is achieved by continu-
ous data clocking to or from multiple registers.
Motion Read is activated by reading the Motion_Burst
register. The ADNS-6000 will respond with the contents
of the Motion, Delta_X, Delta_Y, SQUAL, Shutter_Upper,
Shutter_Lower and Maximum_Pixel registers in that
order. SROM download uses Burst Mode to load the
Avago Technologies-supplied fi rmware fi le contents into
the ADNS-6000. The fi rmware fi le is an ASCII text fi le with
each 2-character byte on a single line. Frame Capture is
a fast way to download a full array of pixel values from a
single frame.
To learn more about sensor’s technical information, please
visit the Avago Technologies web site at http://www.
avagotech.com
Mouse Optics
The motion of Z-wheel is detected using the traditional
method by decoding the quadrature signal generated by
optical sensors. Two phototransistors are connected in
a source-follower confi guration. An infrared LED shines,
causing the phototransistors to turn on. In between the
phototransistors and LED is a pinwheel that turns on the
mouse ball rollers. The fan of this pinwheel is mechanical-
ly designed to block the infrared light such that the pho-
totransistors are turned on and off in a quadrature output
pattern. Every change in the phototransistor outputs rep-
resents a count of mouse movement. Comparing the last
state of the optics to the current state derives direction
information. As shown in Figure 2 below, traveling along
the quadrature signal to the right produces a unique set
of state transitions, and traveling to the left produces
another set of unique state transitions. In this reference
design, only the motion at the Z-wheel is detected using
this method.
