Overview

The MCUXpresso SDK provides a peripheral driver for the Capacitive Touch (CAPT) module of MCUXpresso SDK devices.

The Capacitive Touch module measures the change in capacitance of an electrode plate when an earth-ground connected object (for example, the finger or stylus) is brought within close proximity. Simply stated, the module delivers a small charge to an X capacitor (a mutual capacitance touch sensor), then transfers that charge to a larger Y capacitor (the measurement capacitor), and counts the number of iterations necessary for the voltage across the Y capacitor to cross a predetermined threshold.

Typical use case

Normal Configuration

See the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/capt/capt_basic.

Files
file	fsl_capt.h

Data Structures
struct	capt_config_t
	The structure for CAPT basic configuration. More...

struct	capt_touch_data_t
	The structure for storing touch data. More...

Enumerations
enum	_capt_xpins { kCAPT_X0Pin = 1U << 0U, kCAPT_X1Pin = 1U << 1U, kCAPT_X2Pin = 1U << 2U, kCAPT_X3Pin = 1U << 3U, kCAPT_X4Pin = 1U << 4U, kCAPT_X5Pin = 1U << 5U, kCAPT_X6Pin = 1U << 6U, kCAPT_X7Pin = 1U << 7U, kCAPT_X8Pin = 1U << 8U, kCAPT_X9Pin = 1U << 9U, kCAPT_X10Pin = 1U << 10U, kCAPT_X11Pin = 1U << 11U, kCAPT_X12Pin = 1U << 12U, kCAPT_X13Pin = 1U << 13U, kCAPT_X14Pin = 1U << 14U, kCAPT_X15Pin = 1U << 15U }
	The enumeration for X pins. More...

enum	_capt_interrupt_enable { kCAPT_InterruptOfYesTouchEnable, kCAPT_InterruptOfNoTouchEnable, kCAPT_InterruptOfPollDoneEnable = CAPT_INTENSET_POLLDONE_MASK, kCAPT_InterruptOfTimeOutEnable = CAPT_INTENSET_TIMEOUT_MASK, kCAPT_InterruptOfOverRunEnable = CAPT_INTENSET_OVERUN_MASK }
	The enumeration for enabling/disabling interrupts. More...

enum	_capt_interrupt_status_flags { kCAPT_InterruptOfYesTouchStatusFlag = CAPT_INTSTAT_YESTOUCH_MASK, kCAPT_InterruptOfNoTouchStatusFlag = CAPT_INTSTAT_NOTOUCH_MASK, kCAPT_InterruptOfPollDoneStatusFlag = CAPT_INTSTAT_POLLDONE_MASK, kCAPT_InterruptOfTimeOutStatusFlag = CAPT_INTSTAT_TIMEOUT_MASK, kCAPT_InterruptOfOverRunStatusFlag = CAPT_INTSTAT_OVERUN_MASK }
	The enumeration for interrupt status flags. More...

enum	_capt_status_flags { kCAPT_BusyStatusFlag = CAPT_STATUS_BUSY_MASK, kCAPT_XMAXStatusFlag = CAPT_STATUS_XMAX_MASK }
	The enumeration for CAPT status flags. More...

enum	capt_trigger_mode_t { kCAPT_YHPortTriggerMode = 0U, kCAPT_ComparatorTriggerMode = 1U }
	The enumeration for CAPT trigger mode. More...

enum	capt_inactive_xpins_mode_t { kCAPT_InactiveXpinsHighZMode, kCAPT_InactiveXpinsDrivenLowMode }
	The enumeration for the inactive X pins mode. More...

enum	capt_measurement_delay_t { kCAPT_MeasureDelayNoWait = 0U, kCAPT_MeasureDelayWait3FCLKs = 1U, kCAPT_MeasureDelayWait5FCLKs = 2U, kCAPT_MeasureDelayWait9FCLKs = 3U }
	The enumeration for the delay of measuring voltage state. More...

enum	capt_reset_delay_t { kCAPT_ResetDelayNoWait = 0U, kCAPT_ResetDelayWait3FCLKs = 1U, kCAPT_ResetDelayWait5FCLKs = 2U, kCAPT_ResetDelayWait9FCLKs = 3U }
	The enumeration for the delay of reseting or draining Cap. More...

enum	capt_polling_mode_t { kCAPT_PollInactiveMode, kCAPT_PollNowMode = 1U, kCAPT_PollContinuousMode }
	The enumeration of CAPT polling mode. More...

enum	capt_dma_mode_t { kCAPT_DMATriggerOnTouchMode = 1U, kCAPT_DMATriggerOnBothMode = 2U, kCAPT_DMATriggerOnAllMode = 3U }
	The enumeration of CAPT DMA trigger mode. More...

Variables
bool	capt_config_t::enableWaitMode
	If enable the wait mode, when the touch event occurs, the module will wait until the TOUCH register is read before starting the next measurement. More...

bool	capt_config_t::enableTouchLower
	enableTouchLower = true: Trigger at count < TCNT is a touch. More...

uint8_t	capt_config_t::clockDivider
	Function clock divider. More...

uint8_t	capt_config_t::timeOutCount
	Sets the count value at which a time-out event occurs if a measurement has not triggered. More...

uint8_t	capt_config_t::pollCount
	Sets the time delay between polling rounds (successive sets of X measurements). More...

uint16_t	capt_config_t::enableXpins
	Selects which of the available X pins are enabled. More...

capt_trigger_mode_t	capt_config_t::triggerMode
	Select the menthods of measuring the voltage across the measurement capacitor. More...

capt_inactive_xpins_mode_t	capt_config_t::XpinsMode
	Determines how X pins enabled in the XPINSEL field are controlled when not active. More...

capt_measurement_delay_t	capt_config_t::mDelay
	Set the time delay after entering step 3 (measure voltage state), before sampling the YH port pin or analog comarator output. More...

capt_reset_delay_t	capt_config_t::rDelay
	Set the number of divided FCLKs the module will remain in Reset or Draining Cap. More...

bool	capt_touch_data_t::yesTimeOut
	'true': if the measurement resulted in a time-out event, 'false': otherwise. More...

bool	capt_touch_data_t::yesTouch
	'true': if the trigger is due to a touch even, 'false': if the trigger is due to a no-touch event. More...

uint8_t	capt_touch_data_t::XpinsIndex
	Contains the index of the X pin for the current measurement, or lowest X for a multiple-pin poll now measurement. More...

uint8_t	capt_touch_data_t::sequenceNumber
	Contains the 4-bit(0-7) sequence number, which increments at the end of each polling round. More...

uint16_t	capt_touch_data_t::count
	Contains the count value reached at trigger or time-out. More...

Driver version
#define	FSL_CAPT_DRIVER_VERSION (MAKE_VERSION(2, 0, 1))
	CAPT driver version 2.0.1. More...

Initialization
void	CAPT_Init (CAPT_Type base, const capt_config_t config)
	Initialize the CAPT module. More...

void	CAPT_Deinit (CAPT_Type *base)
	De-initialize the CAPT module. More...

void	CAPT_GetDefaultConfig (capt_config_t *config)
	Gets an available pre-defined settings for the CAPT's configuration. More...

static void	CAPT_SetThreshold (CAPT_Type *base, uint32_t count)
	Set Sets the count threshold in divided FCLKs between touch and no-touch. More...

void	CAPT_SetPollMode (CAPT_Type *base, capt_polling_mode_t mode)
	Set the CAPT polling mode. More...

static void	CAPT_EnableInterrupts (CAPT_Type *base, uint32_t mask)
	Enable interrupt features. More...

static void	CAPT_DisableInterrupts (CAPT_Type *base, uint32_t mask)
	Disable interrupt features. More...

static uint32_t	CAPT_GetInterruptStatusFlags (CAPT_Type *base)
	Get CAPT interrupts' status flags. More...

static void	CAPT_ClearInterruptStatusFlags (CAPT_Type *base, uint32_t mask)
	Clear the interrupts' status flags. More...

static uint32_t	CAPT_GetStatusFlags (CAPT_Type *base)
	Get CAPT status flags. More...

bool	CAPT_GetTouchData (CAPT_Type base, capt_touch_data_t data)
	Get CAPT touch data. More...

Data Structure Documentation

struct capt_config_t

Data Fields
bool	enableWaitMode
	If enable the wait mode, when the touch event occurs, the module will wait until the TOUCH register is read before starting the next measurement. More...

bool	enableTouchLower
	enableTouchLower = true: Trigger at count < TCNT is a touch. More...

uint8_t	clockDivider
	Function clock divider. More...

uint8_t	timeOutCount
	Sets the count value at which a time-out event occurs if a measurement has not triggered. More...

uint8_t	pollCount
	Sets the time delay between polling rounds (successive sets of X measurements). More...

uint16_t	enableXpins
	Selects which of the available X pins are enabled. More...

capt_trigger_mode_t	triggerMode
	Select the menthods of measuring the voltage across the measurement capacitor. More...

capt_inactive_xpins_mode_t	XpinsMode
	Determines how X pins enabled in the XPINSEL field are controlled when not active. More...

capt_measurement_delay_t	mDelay
	Set the time delay after entering step 3 (measure voltage state), before sampling the YH port pin or analog comarator output. More...

capt_reset_delay_t	rDelay
	Set the number of divided FCLKs the module will remain in Reset or Draining Cap. More...

struct capt_touch_data_t

Data Fields
bool	yesTimeOut
	'true': if the measurement resulted in a time-out event, 'false': otherwise. More...

bool	yesTouch
	'true': if the trigger is due to a touch even, 'false': if the trigger is due to a no-touch event. More...

uint8_t	XpinsIndex
	Contains the index of the X pin for the current measurement, or lowest X for a multiple-pin poll now measurement. More...

uint8_t	sequenceNumber
	Contains the 4-bit(0-7) sequence number, which increments at the end of each polling round. More...

uint16_t	count
	Contains the count value reached at trigger or time-out. More...

Macro Definition Documentation

#define FSL_CAPT_DRIVER_VERSION (MAKE_VERSION(2, 0, 1))

Enumeration Type Documentation

enum _capt_xpins

Enumerator
kCAPT_X0Pin	CAPT_X0 pin.
kCAPT_X1Pin	CAPT_X1 pin.
kCAPT_X2Pin	CAPT_X2 pin.
kCAPT_X3Pin	CAPT_X3 pin.
kCAPT_X4Pin	CAPT_X4 pin.
kCAPT_X5Pin	CAPT_X5 pin.
kCAPT_X6Pin	CAPT_X6 pin.
kCAPT_X7Pin	CAPT_X7 pin.
kCAPT_X8Pin	CAPT_X8 pin.
kCAPT_X9Pin	CAPT_X9 pin.
kCAPT_X10Pin	CAPT_X10 pin.
kCAPT_X11Pin	CAPT_X11 pin.
kCAPT_X12Pin	CAPT_X12 pin.
kCAPT_X13Pin	CAPT_X13 pin.
kCAPT_X14Pin	CAPT_X14 pin.
kCAPT_X15Pin	CAPT_X15 pin.

enum _capt_interrupt_enable

Enumerator
kCAPT_InterruptOfYesTouchEnable	Generate interrupt when a touch has been detected.
kCAPT_InterruptOfNoTouchEnable	Generate interrupt when a no-touch has been detected.
kCAPT_InterruptOfPollDoneEnable	Genarate interrupt at the end of a polling round, or when a POLLNOW completes.
kCAPT_InterruptOfTimeOutEnable	Generate interrupt when the count reaches the time-out count value before a trigger occurs.
kCAPT_InterruptOfOverRunEnable	Generate interrupt when the Touch Data register has been up-dated before software has read the previous data, and the touch has been detected.

enum _capt_interrupt_status_flags

Enumerator
kCAPT_InterruptOfYesTouchStatusFlag	YESTOUCH interrupt status flag.
kCAPT_InterruptOfNoTouchStatusFlag	NOTOUCH interrupt status flag.
kCAPT_InterruptOfPollDoneStatusFlag	POLLDONE interrupt status flag.
kCAPT_InterruptOfTimeOutStatusFlag	TIMEOUT interrupt status flag.
kCAPT_InterruptOfOverRunStatusFlag	OVERRUN interrupt status flag.

enum _capt_status_flags

Enumerator
kCAPT_BusyStatusFlag	Set while a poll is currently in progress, otherwise cleared.
kCAPT_XMAXStatusFlag	The maximum number of X pins available for a given device is equal to XMAX+1.

enum capt_trigger_mode_t

Enumerator
kCAPT_YHPortTriggerMode	YH port pin trigger mode.
kCAPT_ComparatorTriggerMode	Analog comparator trigger mode.

enum capt_inactive_xpins_mode_t

Enumerator
kCAPT_InactiveXpinsHighZMode	Xpins enabled in the XPINSEL field are controlled to HIGH-Z mode when not active.
kCAPT_InactiveXpinsDrivenLowMode	Xpins enabled in the XPINSEL field are controlled to be driven low mode when not active.

enum capt_measurement_delay_t

Enumerator
kCAPT_MeasureDelayNoWait	Don’t wait.
kCAPT_MeasureDelayWait3FCLKs	Wait 3 divided FCLKs.
kCAPT_MeasureDelayWait5FCLKs	Wait 5 divided FCLKs.
kCAPT_MeasureDelayWait9FCLKs	Wait 9 divided FCLKs.

enum capt_reset_delay_t

Enumerator
kCAPT_ResetDelayNoWait	Don’t wait.
kCAPT_ResetDelayWait3FCLKs	Wait 3 divided FCLKs.
kCAPT_ResetDelayWait5FCLKs	Wait 5 divided FCLKs.
kCAPT_ResetDelayWait9FCLKs	Wait 9 divided FCLKs.

enum capt_polling_mode_t

Enumerator

kCAPT_PollInactiveMode

No measurements are taken, no polls are performed.

The module remains in the Reset Cap.

kCAPT_PollNowMode

Immediately launches (ignoring Poll Delay) a one-time-only, simultaneous poll of all X pins that are enabled in the XPINSEL field of the Control register, then stops, returning to Reset/Draining Cap.

kCAPT_PollContinuousMode

Polling rounds are continuously performed, by walking through the enabled X pins.

enum capt_dma_mode_t

Enumerator
kCAPT_DMATriggerOnTouchMode	Trigger on touch.
kCAPT_DMATriggerOnBothMode	Trigger on both touch and no-touch.
kCAPT_DMATriggerOnAllMode	Trigger on all touch, no-touch and time-out.

Function Documentation

void CAPT_Init	(	CAPT_Type *	base,
		const capt_config_t *	config
	)

Parameters

base	CAPT peripheral base address.
config	Pointer to "capt_config_t" structure.

void CAPT_Deinit ( CAPT_Type * base )

Parameters

base	CAPT peripheral base address.

void CAPT_GetDefaultConfig ( capt_config_t * config )

This function initializes the converter configuration structure with available settings. The default values are:

*   config->enableWaitMode = false;
*   config->enableTouchLower = true;
*   config->clockDivider = 15U;
*   config->timeOutCount = 12U;
*   config->pollCount = 0U;
*   config->enableXpins = 0U;
*   config->triggerMode = kCAPT_YHPortTriggerMode;
*   config->XpinsMode = kCAPT_InactiveXpinsDrivenLowMode;
*   config->mDelay = kCAPT_MeasureDelayNoWait;
*   config->rDelay = kCAPT_ResetDelayWait9FCLKs;
* 

Parameters

base	CAPT peripheral base address.
config	Pointer to the configuration structure.

static void CAPT_SetThreshold	(	CAPT_Type *	base,
		uint32_t	count
	)

inlinestatic

Parameters

base	CAPT peripheral base address.
count	The count threshold.

void CAPT_SetPollMode	(	CAPT_Type *	base,
		capt_polling_mode_t	mode
	)

Parameters

base	CAPT peripheral base address.
mode	The selection of polling mode.

static void CAPT_EnableInterrupts	(	CAPT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	CAPT peripheral base address.
mask	The mask of enabling interrupt features. Please refer to "_capt_interrupt_enable".

static void CAPT_DisableInterrupts	(	CAPT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	CAPT peripheral base address.
mask	The mask of disabling interrupt features. Please refer to "_capt_interrupt_enable".

static uint32_t CAPT_GetInterruptStatusFlags ( CAPT_Type * base )

inlinestatic

Parameters

base	CAPT peripheral base address.

Returns: The mask of interrupts' status flags. please refer to "_capt_interrupt_status_flags".

static void CAPT_ClearInterruptStatusFlags	(	CAPT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	CAPT peripheral base address.
mask	The mask of clearing the interrupts' status flags, please refer to "_capt_interrupt_status_flags".

static uint32_t CAPT_GetStatusFlags ( CAPT_Type * base )

inlinestatic

Parameters

base	CAPT peripheral base address.

Returns: The mask of CAPT status flags. Please refer to "_capt_status_flags" Or use CAPT_GET_XMAX_NUMBER(mask) to get XMAX number.

bool CAPT_GetTouchData	(	CAPT_Type *	base,
		capt_touch_data_t *	data
	)

Parameters

base	CAPT peripheral base address.
data	The structure to store touch data.

Returns: If return 'true', which means get valid data. if return 'false', which means get invalid data.

Variable Documentation

bool capt_config_t::enableWaitMode

Other-wise, measurements continue.

bool capt_config_t::enableTouchLower

Trigger at count > TCNT is a no-touch. enableTouchLower = false: Trigger at count > TCNT is a touch. Trigger at count < TCNT is a no-touch. Notice: TCNT will be set by "CAPT_DoCalibration" API.

uint8_t capt_config_t::clockDivider

The function clock is divided by clockDivider+1 to produce the divided FCLK for the module. The available range is 0-15.

uint8_t capt_config_t::timeOutCount

The time-out count value is calculated as 2^timeOutCount. The available range is 0-12.

uint8_t capt_config_t::pollCount

After each polling round completes, the module will wait 4096 x PollCount divided FCLKs before starting the next polling round. The available range is 0-255.

uint16_t capt_config_t::enableXpins

Please refer to '_capt_xpins'. For example, if want to enable X0, X2 and X3 pins, you can set "enableXpins = kCAPT_X0Pin | kCAPT_X2Pin | kCAPT_X3Pin".

capt_trigger_mode_t capt_config_t::triggerMode

capt_inactive_xpins_mode_t capt_config_t::XpinsMode

capt_measurement_delay_t capt_config_t::mDelay

capt_reset_delay_t capt_config_t::rDelay

bool capt_touch_data_t::yesTimeOut

bool capt_touch_data_t::yesTouch

uint8_t capt_touch_data_t::XpinsIndex

uint8_t capt_touch_data_t::sequenceNumber

uint16_t capt_touch_data_t::count

Overview

Typical use case

Normal Configuration

Files

Data Structures

Enumerations

Variables

Driver version

Initialization

Data Structure Documentation

Data Fields

Data Fields

Macro Definition Documentation

Enumeration Type Documentation

Function Documentation

Variable Documentation