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BT817A Automotive Advanced Video Engine Datasheet

Version 1.0

Document No.: BRT_000251 Clearance No.: BRT#194

uint16_t main = FW_RD(0) & 0xfff;

uint16_t i_set = 0x4000 | (main - 4);

uint16_t patch = main + 1;

uint16_t i_eol = FW_RD(patch);

while (num_regs--) {

uint8_t reg = *reg_value++;

uint8_t val = *reg_value++;

FW_WR(patch++, 0x8000 | val);

FW_WR(patch++, 0x8000 | reg);

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 BT817A touch engine will send a reset to the CTPM, thus

re-enabling the touch detection function.

4.8.5 Host Driven Multi-Touch

If the host MCU can provide touch inputs, it can supply them directly to the BT817A using touch host

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

the BT817A 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 BT817A 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 BT817A 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 4-8 Touch Host Mode Connections

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

BT817

address

Bits

Description

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