FT800 datasheet(30/55 Pages) FTDI

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Document No.: FT_000792

FT800

Embedded Video Engine

Datasheet Version 1.1

Clearance No.: FTDI# 334

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

REG_TOUCH_MODE.

Table 4-14 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 MPU write '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 in register

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.

4.8 Power Management

4.8.1 Power supply

The FT800 may be operated with a single supply of 3.3V apply to VCC and VCCIO pins. For

operation with host MPU/MCU at lower supply, connect the VCCIO to MPU power to match the

interface power.

Table 4-15 Power supply

Symbol

Typical

Description

VCCIO

1.8V, or 2.5V, or 3.3V

Supply for Host interface digital I/O

pad only, LCD RGB interface supply

from VCC.

VCC

3.3V

Supply for chip

FT800 Datasheet(PDF) 30 Page - Future Technology Devices International Ltd.

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