4-wire resistive touch driver general implementation
[General touch driver]

Collaboration diagram for 4-wire resistive touch driver general implementation:

Modules
	XMEGA 4-wire resistive touch driver internals
Enumerations
enum	touch_states { TOUCH_DISABLED, TOUCH_NOT_TOUCHED, TOUCH_READING_X, TOUCH_READING_Y, TOUCH_PROCESSING, TOUCH_TOUCHED }
	Driver state names. More...
Functions
static void	touch_priv_port_handler (void *int_data)
	Interrupt handler for touch detection.
static void	touch_priv_adc_handler (void *int_data)
	Interrupt handler for AD conversions.
static void	touch_priv_process_samples (void *int_data)
	Process touch samples.
void	touch_init (void)
	Initialize the touch driver.
void	touch_enable (void)
	Enable touch detection and sampling.
void	touch_disable (void)
	Disable touch detection and sampling.
void	touch_get_event (struct touch_event *buffer)
	Get last detected touch event from driver to buffer.
bool	touch_is_touched (void)
	Return current state of touch driver.
void	touch_set_event_handler (touch_event_handler_t handler)
	Set touch event handler for driver.
touch_event_handler_t	touch_get_event_handler (void)
	Get current touch event handler from driver.
void	touch_set_calibration_matrix (const struct touch_calibration_matrix *matrix)
	Assign a calibration matrix to the driver.
void	touch_get_calibration_matrix (struct touch_calibration_matrix *buffer)
	Copy calibration matrix from driver to a buffer.
void	touch_compute_calibration_matrix (const touch_calibration_points_t points, struct touch_calibration_matrix *matrix)
	Compute a calibration matrix.
Variables
static enum touch_states	touch_state
	Current driver state.
static struct touch_event	touch_last_event
	Last detected touch event.
static uint16_t	touch_raw_x
	Temporary raw sample value for X surface.
static uint16_t	touch_raw_y
	Temporary raw sample value for Y surface.
static struct touch_calibration_matrix	touch_matrix
	Calibration matrix for the driver.
touch_event_handler_t	touch_event_handler
	Current touch event handler (set to NULL if no handler should be called).
Definition of interrupt handlers for touch detection and reading

	INTC_DEFINE_HANDLER (CONFIG_TOUCH_PORT_IRQ_ID, touch_priv_port_handler, CONFIG_TOUCH_PORT_INTLVL)
	INTC_DEFINE_HANDLER (CONFIG_TOUCH_ADC_IRQ_ID, touch_priv_adc_handler, CONFIG_TOUCH_ADC_INTLVL)

Detailed Description

This driver makes use of low level interrupts for touch detection, and an ADC for touch position measurements.

Enumeration Type Documentation

enum touch_states

Driver state names.

Enumerator:

TOUCH_DISABLED	Driver is disabled, no sampling will occur.
TOUCH_NOT_TOUCHED	Driver enabled, but panel not touched.
TOUCH_READING_X	Waiting for samples for X coordinate.
TOUCH_READING_Y	Waiting for samples for Y coordinate.
TOUCH_PROCESSING	Waiting for processing of samples.
TOUCH_TOUCHED	Panel is currently touched.

Definition at line 63 of file touch.c.

Function Documentation

void touch_compute_calibration_matrix	(	const touch_calibration_points_t	points,
		struct touch_calibration_matrix *	matrix
	)

Compute a calibration matrix.

Computes the calibration matrix that is used to get the panel coordinates from raw measurements of the touch surface.
This requires that the

Note:: Reference: http://www.embedded.com/story/OEG20020529S0046

Parameters:

	points	Pointer to array containing calibration points.
	matrix	Pointer to storage buffer for the calibration matrix.

Definition at line 270 of file touch.c.

References touch_calibration_matrix::a, assert, touch_calibration_matrix::b, touch_calibration_matrix::c, touch_calibration_matrix::d, touch_calibration_matrix::e, touch_calibration_matrix::f, and touch_calibration_matrix::k.

Referenced by touch_calibrate_task_handler().

void touch_disable ( void )

Disable touch detection and sampling.

Disables interrupts for the GPIO and the ADC.

Definition at line 160 of file touch.c.

References cpu_irq_restore(), cpu_irq_save(), touch_priv_adc_disable_int(), and touch_priv_port_disable_int().

Referenced by touch_init().

void touch_enable ( void )

Enable touch detection and sampling.

Resets the driver and touch state, configures GPIO pins for touch detection and enables interrupts for GPIO and the ADC.

Definition at line 137 of file touch.c.

References touch_last_event, TOUCH_NOT_TOUCHED, touch_priv_adc_clear_int_flag(), touch_priv_adc_enable_int(), touch_priv_port_clear_int_flag(), touch_priv_port_enable_int(), touch_priv_port_set_detection(), touch_state, and touch_event::type.

void touch_get_calibration_matrix ( struct touch_calibration_matrix * buffer )

Copy calibration matrix from driver to a buffer.

Parameters:

buffer

Address of buffer to copy calibration matrix to.

Definition at line 250 of file touch.c.

References assert, and touch_matrix.

void touch_get_event ( struct touch_event * buffer )

Get last detected touch event from driver to buffer.

Parameters:

buffer

Buffer to store touch event in.

Definition at line 179 of file touch.c.

References assert, cpu_irq_restore(), cpu_irq_save(), and touch_last_event.

touch_event_handler_t touch_get_event_handler ( void )

Get current touch event handler from driver.

Returns:: Address of the currently set handler function.

Definition at line 226 of file touch.c.

References touch_event_handler.

void touch_init ( void )

Initialize the touch driver.

Initializes the GPIO pins and ADC for touch detection and measurements, as well as the driver states.
Must be called before any other function in this driver.

Note:: The touch driver is left disabled, and must be explicitly enabled by use of touch_enable().

Definition at line 111 of file touch.c.

References softirq_set_handler(), touch_disable(), touch_event_handler, touch_last_event, TOUCH_NOT_TOUCHED, touch_priv_adc_init(), touch_priv_port_init(), touch_priv_process_samples(), touch_state, and touch_event::type.

bool touch_is_touched ( void )

Return current state of touch driver.

Return values:

	true	Driver is sensing a touch.
	false	Driver is not sensing a touch.

Definition at line 198 of file touch.c.

References touch_last_event, and touch_event::type.

void touch_priv_adc_handler ( void * int_data ) [static]

Interrupt handler for AD conversions.

Handles and triggers raw measurements of position on the touch surfaces.
After measurements are completed, a soft IRQ is either raised or touch_priv_process_samples() called directly, depending on configuration.

Parameters:

int_data

Not used here.

Definition at line 460 of file touch.c.

References assert, softirq_raise(), touch_priv_adc_get_x(), touch_priv_adc_get_y, touch_priv_adc_set_surface_y(), touch_priv_adc_start(), touch_priv_port_set_detection(), touch_priv_port_set_gradient_y(), touch_priv_process_samples(), TOUCH_PROCESSING, touch_raw_x, touch_raw_y, TOUCH_READING_X, TOUCH_READING_Y, and touch_state.

void touch_priv_port_handler ( void * int_data ) [static]

Interrupt handler for touch detection.

Disables itself and triggers the first touch position measurement.
The first measurements are done on the X surface of the touch panel.

Parameters:

int_data

Not used here.

Definition at line 430 of file touch.c.

References assert, TOUCH_NOT_TOUCHED, touch_priv_adc_set_surface_x(), touch_priv_adc_start(), touch_priv_port_disable_int(), touch_priv_port_set_gradient_x(), touch_raw_x, touch_raw_y, TOUCH_READING_X, touch_state, and TOUCH_TOUCHED.

void touch_priv_process_samples ( void * int_data ) [static]

Process touch samples.

Uses the calibration matrix to compute touch position in panel coordinates from the current raw touch measurements.
The driver and touch states are updated according to the event, and its handler (if set) is called if a new event was in fact detected.

Parameters:

int_data

Not used here.

Definition at line 330 of file touch.c.

References touch_calibration_matrix::a, touch_calibration_matrix::b, touch_calibration_matrix::c, touch_calibration_matrix::d, touch_calibration_matrix::e, touch_calibration_matrix::f, touch_calibration_matrix::k, touch_point::panel_x, touch_point::panel_y, touch_event::point, touch_point::raw_x, touch_point::raw_y, touch_event_handler, touch_last_event, touch_matrix, TOUCH_NOT_TOUCHED, touch_priv_port_clear_int_flag(), touch_priv_port_enable_int(), touch_priv_port_is_int_flag_set(), touch_raw_x, touch_raw_y, touch_state, TOUCH_TOUCHED, and touch_event::type.