BT815Q-R datasheet(36/64 Pages) BRIDGETEK

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BT81X (815/6) Advanced Embedded Video Engine Datasheet

Version 1.0

Document No.: BRT_000220 Clearance No.: BRT#126

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

data to the BT815 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 4-11 Touch Host Mode Connections

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

BT815

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 4-19

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 the host

writes 0xf to the ID register, BT815 sets the ACK register to 0, transforms all the raw coordinates, and

writes the results to the regular touch registers.

Pseudocode:

wait until REG_EHOST_TOUCH_ACK is 1

for each touch:

write x coordinate to REG_EHOST_TOUCH_X

write y coordinate to REG_EHOST_TOUCH_Y

write id to REG_EHOST_TOUCH_ID

write 0xf to REG_EHOST_TOUCH_ID

As soon as BT815 has converted the coordinates, it writes 1 to the ACK register and sets the INT_CONV

_COMPLETE interrupt flag.

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