VT5366V032 datasheet(17/30 Pages) STMICROELECTRONICS

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VT5366

Operation

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5.5

Operating mode

The VT5366 itself has only two operating modes; ON - when PowerDown = 0 and OFF -

when PowerDown = 1

Overall system behavior is controlled by the external microprocessor which can switch the

VT5366 on and off with various duty cycles. Typical operation is described below.

The processor enables the VT5366 by setting PowerDown (pin 23) LOW.

The processor delays for Ton (typically 250µs) to allow some frames to be captured.

The processor then monitors Motion Detect to see if motion has occurred. If Motion

Detect (pin 24) = 0 then no motion has been detected and the VT5366 can be put back

to sleep by setting PowerDown HIGH.

The processor then waits for a time Tsleep and returns to step (1).

If motion IS detected at step (3) i.e. Motion Detect = 1 then the motion vectors are read

over the I2C interface. The processor can then monitor Motion Detect again to see if

further motion has occurred.

5.6

Motion sensitivity in non RUN modes

Before going into a non-run mode write 0x40 to register 0x2F (ie. when the mouse goes into

idle mode), this will make the motion engine more sensitive to frame change at lower non-

run frame rates on low contrast surfaces.

When waking up (on motion detect) re-write the default 0x10 to register 0x2F to maintain

running motion accuracy.

5.7

Overall system performance

The overall performance of a wireless mouse system depends on many different factors

including:

–

Battery choice

–

Power supply design

–

Choice of external microprocessor

–

Design of firmware running in external processor

–

Design of external RF transmission circuitry

–

User model i.e. how much time the mouse is actually being used and surface type.

Note:

See Applications Note AN2473 for details on Optical Wireless Mouse Design using the

VT5366.

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