FT810Q datasheet(33/60 Pages) FTDI

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Document No.: FT_001165

FT81X

Embedded Video Engine

Datasheet Version 1.2

Clearance No.:

FTDI#440

The host controls the TOUCH SCREEN ENGINE operation mode by writing the REG_TOUCH_MODE.

Table 4-17 Resistive Touch Controller Operating Mode

REG_TOUCH_MODE

Mode

Description

OFF

Acquisition stopped, only touch detection interrupt is still valid.

ONE-SHOT

Perform acquisition once every time the MPU writes '1' to

REG_TOUCH_MODE.

FRAME-SYNC

Perform acquisition for every frame sync (~60 data

acquisition/second.

CONTINUOUS

Perform acquisition continuously at approximately 1000 data

acquisition / second.

The Touch Screen Engine captures the raw X and Y coordinate and writes to register REG_TOUCH_RAW

XY. The range of these values is 0-1023. If the touch screen is not being pressed, both registers read

65535 (FFFFh).

These touch values are transformed into screen coordinates using the matrix in registers

REG_TOUCH_TRANSFORM_A-F.

The

post-transform

coordinates

are

available

REG_TOUCH_SCREEN_XY. If the touch screen is not being pressed, both registers read -32768 (8000h).

The values for REG TOUCH TRANSFORM A-F may be computed using an on-screen calibration process.

If the screen is being touched, the screen coordinates are looked up in the screen's tag buffer, delivering

a final 8-bit tag value, in REG TOUCH TAG. Because the tag lookup takes a full frame, and touch

coordinates change continuously, the original (x; y) used for the tag lookup is also available in

REG_TOUCH_TAG_XY.

Screen touch pressure is available in REG_TOUCH_RZ. The value is relative to the resistance of the touch

contact, a lower value indicates more pressure. The register defaults to 32767 when touch is not

detected. The REG_TOUCH_THRESHOLD can be set to accept a touch only when the force threshold is

exceeded.

4.7.2 Capacitive Touch Control

The Capacitive Touch Screen Engine (CTSE) of the FT81x communicates with the external capacitive

touch panel module (CTPM) through an I2C interface. The CTPM will assert its interrupt line when there is

a touch detected. Upon detecting CTP_INT_N line active, the FT81x will read the touch data through I2C.

Up to 5 touches can be reported and stored in FT81x registers.

For a supported CTPM list please consult FTDI website.

FT810Q Datasheet(PDF) 33 Page - Future Technology Devices International Ltd.

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