TouchDriverBitBang Class Reference

Bit-banged 4-wire resistive touch panel driver. More...

#include <TouchDriverArduino.h>

Inheritance diagram for TouchDriverBitBang:

Collaboration diagram for TouchDriverBitBang:

Public Member Functions
	TouchDriverBitBang (int8_t xPlusPin, int8_t xMinusPin, int8_t yPlusPin, int8_t yMinusPin)
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.
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

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

Bit-banged 4-wire resistive touch panel driver.

Drives the resistive layer's four pins (X-, Y-, X+, Y+) directly via GPIO - pinMode()/digitalWrite()/digitalRead()/analogRead() - rather than through a dedicated touch controller chip such as XPT2046. This matches small resistive touch panels that expose their four resistive-layer pins straight to microcontroller GPIOs instead of routing them through a controller IC.

Requires analogRead() to be available for all four pins, i.e. a real Arduino core (arduino-esp32, AVR, ...) - the ESP-IDF-native TinyGPU/Emulation fallback (see EmulationIDF.h) does not emulate analogRead()/ADC, so this driver will not compile against that fallback.

Position measurement, per axis:

• drive one axis's plates (e.g. X+ HIGH / X- LOW) to set up a voltage gradient across that resistive layer
• float the OTHER axis's plates (INPUT)
• analogRead() one of the other axis's pins: the voltage it picks up is proportional to position along the driven axis

Touch presence is a cheap digital check (Y+ as INPUT_PULLUP, X- driven LOW; a touch shorts the two layers together and pulls Y+ LOW) rather than a calibrated Z1/Z2 pressure measurement - this only needs to know whether the panel is touched at all. Pressure is therefore always reported as 255 while touched, like the capacitive controllers below.

Constructor & Destructor Documentation

TouchDriverBitBang()

TouchDriverBitBang ( int8_t  xPlusPin, int8_t  xMinusPin, int8_t  yPlusPin, int8_t  yMinusPin  )

inline

Parameters

xPlusPin	X+ resistive layer analog pin.
xMinusPin	X- resistive layer digital pin.
yPlusPin	Y+ resistive layer analog pin.
yMinusPin	Y- resistive layer digital pin.

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.

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.

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

• src/TinyGPU/Input/TouchDriverArduino.h