TouchDriverGT911 Class Reference

GT911 capacitive touch controller. More...

#include <TouchDriverArduino.h>

Inheritance diagram for TouchDriverGT911:

Collaboration diagram for TouchDriverGT911:

Public Member Functions
	TouchDriverGT911 (TwoWire &wire=Wire, int8_t rstPin=-1, int8_t irqPin=-1, uint8_t i2cAddr=I2C_ADDR_1)
bool	begin () override
	Initialize the controller.
bool	isTouched () override
	Return whether the panel currently appears touched.
bool	getPoint (Point &outPoint) override
	Read the current touch point.
bool	getSecondPoint (Point &outPoint) override
	Read a second, simultaneous touch point, for multi-touch gestures (pinch/rotate).
Public Member Functions inherited from TouchDriver
virtual	~TouchDriver ()=default
virtual bool	begin ()=0
	Initialize the controller.
virtual bool	isTouched ()=0
	Return whether the panel currently appears touched.
virtual bool	getPoint (Point &outPoint)=0
	Read the current touch point.
virtual bool	getSecondPoint (Point &outPoint)
	Read a second, simultaneous touch point, for multi-touch gestures (pinch/rotate).
void	setRotation (Rotation rotation)
Rotation	getRotation () const
bool	setCalibration (const CalibrationData &cal)
	Set and validate calibration.
const CalibrationData &	getCalibration () const
bool	hasCalibration () const

Static Public Attributes
static constexpr uint8_t	I2C_ADDR_1 = 0x5D
static constexpr uint8_t	I2C_ADDR_2 = 0x14

Additional Inherited Members
Protected Member Functions inherited from TouchDriver
Point	mapCoordinates (int16_t rawX, int16_t rawY, uint16_t pressure=255) const
	Convert raw controller coordinates into logical display space.
Static Protected Member Functions inherited from TouchDriver
static bool	validateCalibration (const CalibrationData &cal)
static int32_t	clamp32 (int32_t value, int32_t minimum, int32_t maximum)
	Clamp an integer to an inclusive range.
static int32_t	mapRange (int32_t value, int32_t inMin, int32_t inMax, int32_t outMin, int32_t outMax)
	Map an integer from one range to another.
Protected Attributes inherited from TouchDriver
Rotation	rotation_ = Rotation::Deg0
CalibrationData	calibration_
bool	hasCalibration_ = false

Detailed Description

GT911 capacitive touch controller.

I2C address is normally 0x5D (alt 0x14, selected via the INT pin's level while RST is pulsed - see begin()). Unlike FT6236/CST816S, GT911's register addresses are 16-bit (MSB first), and its X/Y bytes are little-endian (low byte first) rather than the big-endian nibble-packed layout FT6236 uses.

Register layout used:

0x8100 CONFIG_FRESH: write 1 after reset to make the chip start its sensing engine. Without this, the chip stays fully alive and correctly configured but never scans - status sits at 0x80 ("config loaded, idle") forever. 0x80FF config checksum: round-tripped (read then written back unchanged) alongside the CONFIG_FRESH write. 0x814E status: bit7 = buffer ready, bits[3:0] = touch point count. Must be cleared (write 0x00) unconditionally on every poll, not only when a touch was found - clearing it only after a detected touch is a deadlock, since a stale, unacknowledged flag prevents the chip from ever reporting a new one. 0x814F point 0 data (7 bytes: track_id, x_lo, x_hi, y_lo, y_hi, size_lo, size_hi); point N starts at 0x814F + N*7.

Because status must be cleared unconditionally exactly once per poll cycle, isTouched() does the chip's actual read/clear I/O and caches whatever point data was present; getPoint()/getSecondPoint() just return the cached result rather than re-querying the chip. Call isTouched() once per loop iteration (the same usage pattern as this file's other touch drivers) - calling it more than once between getPoint() calls will consume/clear a pending touch before getPoint() sees it.

GT911 genuinely reports up to 5 simultaneous touches (unlike the single-touch FT6236/CST816S/XPT2046 parts also in this file), so getSecondPoint() is a real second contact, not a stub.

Constructor & Destructor Documentation

TouchDriverGT911()

TouchDriverGT911 ( TwoWire &  wire = Wire, int8_t  rstPin = -1, int8_t  irqPin = -1, uint8_t  i2cAddr = I2C_ADDR_1  )

inline

Member Function Documentation

begin()

bool begin ( )

inlineoverridevirtual

Initialize the controller.

The driver does NOT initialize the SPI/I2C bus itself. The application is responsible for calling Wire.begin(), SPI.begin(), and configuring any board-specific bus pins.

Implements TouchDriver.

getPoint()

bool getPoint ( Point &  outPoint )

inlineoverridevirtual

Read the current touch point.

Returns

true if a valid touch point was obtained.

Implements TouchDriver.

getSecondPoint()

bool getSecondPoint ( Point &  outPoint )

inlineoverridevirtual

Read a second, simultaneous touch point, for multi-touch gestures (pinch/rotate).

Returns false by default. Only override this if the underlying controller can genuinely report two simultaneous touches - none of the drivers built into this library can (XPT2046 is a resistive, inherently single-touch controller; CST816S/FT6236 are single-touch capacitive parts), so pinch/rotate gestures built on top of this will not fire against them.

Reimplemented from TouchDriver.

isTouched()

bool isTouched ( )

inlineoverridevirtual

Return whether the panel currently appears touched.

For controllers without an IRQ pin this may perform a controller read.

Implements TouchDriver.

Member Data Documentation

I2C_ADDR_1

constexpr uint8_t I2C_ADDR_1 = 0x5D

staticconstexpr

I2C_ADDR_2

constexpr uint8_t I2C_ADDR_2 = 0x14

staticconstexpr

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The documentation for this class was generated from the following file:

• src/TinyGPU/Input/TouchDriverArduino.h