User Manual
17
Figure 11. Directional Orientation
An interrupt is generated based on the number of gesture
“datasets” results placed in the FIFO. A dataset is dened
as 4-byte directional data corresponding to U-D-L-R.The
FIFO can buer up to 32 datasets before it overows. If
the FIFO overows (host did not read quickly enough)
then the most recent data will be lost. If the FIFO level,
GFLVL, becomes greater or equal to the threshold value
set by GFIFOTH, then the GVALID bit is set, indicating valid
data is available; the gesture interrupt bit, GINT, is assert-
ed, and if GIEN bit is set a hardware interrupt on the INT
pin will also assert. Before exit of gesture engine, one nal
interrupt will always occur if GVALID is asserted, signaling
data remains in the FIFO. Gesture Interrupts ags: GINT,
GVALID, and GFLVL are cleared by emptying e. all data has
been read).
The correlation of motion to FIFO data and direction char-
acteristics) is not obvious at rst glance. As depicted in
Figure 12, the four directional sensors are placed in an
orthogonal pattern optically lensed aperture. Diodes are
designated as: U, D, L, R; the 8-bit results corresponding
to each diode is available at the following sequential FIFO
locations: 0xFC, 0xFD, 0xFE, and 0xFF.
Ideally, gesture detection works by capturing and compar-
ing the amplitude and phase dierence between direc-
tional sensor results. The directional sensors are arranged
such that the diode opposite to the directional motion
receives a larger portion of the reected IR signal upon
entry, then a smaller portion upon exit. In the example il-
lustration, a downward or rightward motion of a target is
illustrated per the respective arrows in Figure 11.
Directional Orientation
Counts
Time
Up 0xFC Down 0xFD Left 0xFE Right 0xFF
Counts
Time
Up 0xFC Down 0xFD Left 0xFE Right 0xFF
LED
U
D
L R
Ideal response
Ideal response
Downward
motion
Rightward
motion