FT810Q datasheet(35/60 Pages) FTDI

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Document No.: FT_001165

FT81X

Embedded Video Engine

Datasheet Version 1.2

Clearance No.:

FTDI#440

The five touch coordinates are packed in REG_CTOUCH_TOUCH0_XY, REG_CTOUCH_TOUCH1_XY,

REG_CTOUCH_TOUCH2_XY, REG_CTOUCH_TOUCH3_XY, REG_CTOUCH4_X and REG_CTOUCH4_Y.

Coordinates stored in these registers are signed 16-bit values, so have range -32768 to 32767. The no-

touch condition is indicated by x=y= -32768. These coordinates are already transformed into screen

coordinates based on the raw data read from the CTPM, using the matrix in registers

REG_CTOUCH_TRANSFORM_A-F. To obtain raw (x,y) coordinates read from CTPM, the user sets the

REG_CTOUCH_TRANSFORM_A-F registers to the identity matrix.

The FT81x tag mechanism is implemented by hardware, where up to 5 tags can be looked up.

4.7.5 Short-circuit protection

For resistive touch it is useful to protect the chip from permanent damage due to potential short-circuits

on the 4 XY lines. When a short circuit on the touch screen happens, the FT81x can detect it and stop the

touch detection operation, leaving the 4 XY pins in the high impedance state.

The short-circuit protection can be enabled/disabled by the REG_TOUCH_CONFIG.

4.7.6 Capacitive touch configuration

On capacitive touch system some users may need to adjust the CTPM default values, such as the

registers affecting touch sensitivity. To do this the following sequence shall be executed once after chip

reset:

Hold the touch engine in reset (set REG_CPURESET = 2)

Write the CTPM configure register address and value to FT81x designated memory location

Up to 10 register address/value can be added

Release the touch engine reset (set REG_CPURESET = 0)

The CTPM can be enabled in low power state when the touch function is not required by the application.

Setting the low-power bit in REG_TOUCH_CONFIG will enable the low power mode of the CTPM. When

the low-power bit is cleared, the FT81x touch engine will send a reset to the CTPM, thus re-enabling the

touch detection function.

4.7.7 Touch detection in none-ACTIVE state

When FT81x is in none-ACTIVE state, a touch event can still be detected and reported to the host

through the INT_N pin. In other words, a touch event can wake-up the host if needed.

For resistive touch, the INT_N pin will be asserted low when the screen is touched, regardless of the

setting of the interrupt registers. This will happen when the FT81x is in STANDBY or SLEEP state, but not

in POWERDOWN state.

For capacitive touch, the INT_N pin will follow CTP_INT_N pin when the FT81x is in STANDBY, SLEEP or

POWERDOWN state.

4.8 Power Management

4.8.1 Power supply

The FT81x may be operated with a single supply of 3.3V applied to VCC and VCCIO pins. For operation

with a host MPU/MCU at a lower supply, connect the VCCIO1 to the MPU IO supply to match the interface

voltage. For operation with LCD/touch panels at lower voltages, connect the VCCIO2 to the LCD/touch IO

supply.

FT810Q Datasheet(PDF) 35 Page - Future Technology Devices International Ltd.

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