TMG39921 datasheet(82/96 Pages) OSRAM

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[v1-06] 2018-Feb-27

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TMG3992 − Register Description

Gesture FIFO Access Registers (0xFC − 0xFF)

In Gesture mode, the RAM area is repurposed as a 128 byte FIFO.

Data is stored in four byte blocks. Each block, called a dataset,

contains one integration cycle of North, South, West, & East

gesture data. Thirty-two separate datasets are stored within the

FIFO before wrap-around overflow. If the FIFO overflows (i.e. 33

datasets before host/system can empty FIFO) new datasets will

not replace existing datasets; instead an overflow flag will be

set and new data will be lost.

Host/Systems acquire gesture data by reading addresses: 0xFC,

0xFD, 0xFE, & 0xFF, which directly correspond to North, South,

West, and East data points. Data can be read a single byte at a

time (four consecutive I2C transactions) or by using a page read.

The internal FIFO read pointer and the FIFO Level register,

GFIFOLVL, values are updated when address 0xFF is accessed

(single byte transactions) or when every fourth byte,

corresponding to address 0xFF, is accessed in page mode. If the

FIFO continues to be accessed after GFIFOLVL register is zero,

dataset will be read as zero values.

The recommended procedure for reading data stored in the

FIFO begins when a gesture interrupt is generated (GFIFOLVL >

GFIFOTH). Next, the host reads the FIFO Level register,

GFIFOLVL, to determine the amount of valid data in the FIFO.

Finally, the host begins to read address 0xFC (page read), and

continues to read (clock-out data) until the FIFO is empty

(Number of bytes is 4x GFIFOLVL). For example, if

GFIFOLVL = 2, then the host should initiate a read at address

0xFC, and sequentially read all eight bytes. As the four-byte

blocks are read, GFIFOLVL register is decremented and the

internal FIFO pointers are updated.

Figure 87:

Gesture FIFO Access Registers

Registers

Address

Bits

Description

GFIFO_N

0xFC

7:0

Gesture North FIFO

GFIFO_S

0xFD

7:0

Gesture South FIFO

GFIFO_W

0xFE

7:0

Gesture West FIFO

GFIFO_E

0xFF

7:0

Gesture East FIFO

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