BT817Q-R datasheet(35/59 Pages) BRIDGETEK

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BT817/8 Advanced Embedded Video Engine Datasheet

Version 1.1

Document No.: BRT_000302 Clearance No.: BRT#154

FW_WR(patch++, i_set);

}

FW_WR(patch, i_eol);

VC.wr(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 BT817 touch engine will send a reset to the CTPM, thus

re-enabling the touch detection function.

4.8.7

Host Driven Multi-Touch

If the host MCU can provide touch inputs, it can supply them directly to the BT817 using touch host

mode. By using touch host mode, an application can choose to select a touch controller that is not in

the BT817 direct support list. For example, Touch Host mode would allow controllers to be used from

other manufacturers beyond Focaltech and Goodix.

To use the touch host mode, the host MCU shall be connected to the touch panel directly. The four

touch related pins of the BT817 can be left unconnected on the PCB. The host MCU is responsible for

communicating with the touch controller, fetching the touch data when reported, and writing the touch

data to the BT817 for touch TAG lookup and reporting.

The touch host mode can be entered by setting bit 14 in register REG_TOUCH_CONFIG and resetting

the touch engine:

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

Write 1 to bit 14 in REG_TOUCH_CONFIG (set REG_TOUCH_CONFIG = 0x4000)

Release the touch engine reset (set REG_CPURESET = 0)

Figure 4-9 Touch Host Mode Connections

In touch host mode, the host supplies touch information via four registers:

BT817

address

Bits

Description

0x30210c

REG_EHOST_TOUCH_X

Unsigned

16-bit

Touch x coordinate

0x302118

REG_EHOST_TOUCH_Y

Unsigned

16-bit

Touch y coordinate

0x302114

REG_EHOST_TOUCH_ID

4-bit

Touch ID / phase

0x302170

REG_EHOST_TOUCH_ACK

4-bit

Acknowledgement

Table 4-21

Registers for Touch Host Mode

The host writes raw (x; y) coordinates and IDs to the above registers. Up to 5 touches can be set,

using touch IDs 0-4. The host indicates no touch by supplying coordinates (0x8000; 0x8000). When

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