Overview

The MCUXpresso SDK provides a driver for the Low-Power Interrupt Timer (LPIT) of MCUXpresso SDK devices.

Function groups

The LPIT driver supports operating the module as a time counter.

Initialization and deinitialization

The function LPIT_Init() initializes the LPIT with specified configurations. The function LPIT_GetDefaultConfig() gets the default configurations. The initialization function configures the LPIT operation in doze mode and debug mode.

The function LPIT_SetupChannel() configures the operation of each LPIT channel.

The function LPIT_Deinit() disables the LPIT module and disables the module clock.

Timer period Operations

The function LPITR_SetTimerPeriod() sets the timer period in units of count. Timers begin counting down from the value set by this function until it reaches 0.

The function LPIT_GetCurrentTimerCount() reads the current timer counting value. This function returns the real-time timer counting value, in a range from 0 to a timer period.

The timer period operation functions takes the count value in ticks. User can call the utility macros provided in fsl_common.h to convert to microseconds or milliseconds

Start and Stop timer operations

The function LPIT_StartTimer() starts the timer counting. After calling this function, the timer loads the period value set earlier via the LPIT_SetPeriod() function and starts counting down to 0. When the timer reaches 0, it generates a trigger pulse and sets the timeout interrupt flag.

The function LPIT_StopTimer() stops the timer counting.

Status

Provides functions to get and clear the LPIT status.

Interrupt

Provides functions to enable/disable LPIT interrupts and get current enabled interrupts.

Typical use case

LPIT tick example

Updates the LPIT period and toggles an LED periodically. Refer to the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/lpit

Data Structures
struct	_lpit_chnl_params
	Structure to configure the channel timer. More...

struct	_lpit_config
	LPIT configuration structure. More...

Functions
static void	LPIT_Reset (LPIT_Type *base)
	Performs a software reset on the LPIT module. More...

Driver version
enum	_lpit_chnl { kLPIT_Chnl_0 = 0U, kLPIT_Chnl_1, kLPIT_Chnl_2, kLPIT_Chnl_3 }
	List of LPIT channels. More...

enum	_lpit_timer_modes { kLPIT_PeriodicCounter = 0U, kLPIT_DualPeriodicCounter, kLPIT_TriggerAccumulator, kLPIT_InputCapture }
	Mode options available for the LPIT timer. More...

enum	_lpit_trigger_select { kLPIT_Trigger_TimerChn0 = 0U, kLPIT_Trigger_TimerChn1, kLPIT_Trigger_TimerChn2, kLPIT_Trigger_TimerChn3, kLPIT_Trigger_TimerChn4, kLPIT_Trigger_TimerChn5, kLPIT_Trigger_TimerChn6, kLPIT_Trigger_TimerChn7, kLPIT_Trigger_TimerChn8, kLPIT_Trigger_TimerChn9, kLPIT_Trigger_TimerChn10, kLPIT_Trigger_TimerChn11, kLPIT_Trigger_TimerChn12, kLPIT_Trigger_TimerChn13, kLPIT_Trigger_TimerChn14, kLPIT_Trigger_TimerChn15 }
	Trigger options available. More...

enum	_lpit_trigger_source { kLPIT_TriggerSource_External = 0U, kLPIT_TriggerSource_Internal }
	Trigger source options available. More...

enum	_lpit_interrupt_enable { kLPIT_Channel0TimerInterruptEnable = (1U << 0), kLPIT_Channel1TimerInterruptEnable = (1U << 1), kLPIT_Channel2TimerInterruptEnable = (1U << 2), kLPIT_Channel3TimerInterruptEnable = (1U << 3) }
	List of LPIT interrupts. More...

enum	_lpit_status_flags { kLPIT_Channel0TimerFlag = (1U << 0), kLPIT_Channel1TimerFlag = (1U << 1), kLPIT_Channel2TimerFlag = (1U << 2), kLPIT_Channel3TimerFlag = (1U << 3) }
	List of LPIT status flags. More...

typedef enum _lpit_chnl	lpit_chnl_t
	List of LPIT channels. More...

typedef enum _lpit_timer_modes	lpit_timer_modes_t
	Mode options available for the LPIT timer. More...

typedef enum _lpit_trigger_select	lpit_trigger_select_t
	Trigger options available. More...

typedef enum _lpit_trigger_source	lpit_trigger_source_t
	Trigger source options available.

typedef enum _lpit_interrupt_enable	lpit_interrupt_enable_t
	List of LPIT interrupts. More...

typedef enum _lpit_status_flags	lpit_status_flags_t
	List of LPIT status flags. More...

typedef struct _lpit_chnl_params	lpit_chnl_params_t
	Structure to configure the channel timer. More...

typedef struct _lpit_config	lpit_config_t
	LPIT configuration structure. More...

#define	FSL_LPIT_DRIVER_VERSION (MAKE_VERSION(2, 1, 1))
	Version 2.1.1.

Initialization and deinitialization
void	LPIT_Init (LPIT_Type base, const lpit_config_t config)
	Ungates the LPIT clock and configures the peripheral for a basic operation. More...

void	LPIT_Deinit (LPIT_Type *base)
	Disables the module and gates the LPIT clock. More...

void	LPIT_GetDefaultConfig (lpit_config_t *config)
	Fills in the LPIT configuration structure with default settings. More...

status_t	LPIT_SetupChannel (LPIT_Type base, lpit_chnl_t channel, const lpit_chnl_params_t chnlSetup)
	Sets up an LPIT channel based on the user's preference. More...

Interrupt Interface
static void	LPIT_EnableInterrupts (LPIT_Type *base, uint32_t mask)
	Enables the selected PIT interrupts. More...

static void	LPIT_DisableInterrupts (LPIT_Type *base, uint32_t mask)
	Disables the selected PIT interrupts. More...

static uint32_t	LPIT_GetEnabledInterrupts (LPIT_Type *base)
	Gets the enabled LPIT interrupts. More...

Status Interface
static uint32_t	LPIT_GetStatusFlags (LPIT_Type *base)
	Gets the LPIT status flags. More...

static void	LPIT_ClearStatusFlags (LPIT_Type *base, uint32_t mask)
	Clears the LPIT status flags. More...

Read and Write the timer period
static void	LPIT_SetTimerPeriod (LPIT_Type *base, lpit_chnl_t channel, uint32_t ticks)
	Sets the timer period in units of count. More...

static void	LPIT_SetTimerValue (LPIT_Type *base, lpit_chnl_t channel, uint32_t ticks)
	Sets the timer period in units of count. More...

static uint32_t	LPIT_GetCurrentTimerCount (LPIT_Type *base, lpit_chnl_t channel)
	Reads the current timer counting value. More...

Timer Start and Stop
static void	LPIT_StartTimer (LPIT_Type *base, lpit_chnl_t channel)
	Starts the timer counting. More...

static void	LPIT_StopTimer (LPIT_Type *base, lpit_chnl_t channel)
	Stops the timer counting. More...

Data Structure Documentation

struct _lpit_chnl_params

Data Fields
bool	chainChannel
	true: Timer chained to previous timer; false: Timer not chained

lpit_timer_modes_t	timerMode
	Timers mode of operation. More...

lpit_trigger_select_t	triggerSelect
	Trigger selection for the timer.

lpit_trigger_source_t	triggerSource
	Decides if we use external or internal trigger. More...

bool	enableReloadOnTrigger
	true: Timer reloads when a trigger is detected; false: No effect

bool	enableStopOnTimeout
	true: Timer will stop after timeout; false: does not stop after timeout

bool	enableStartOnTrigger
	true: Timer starts when a trigger is detected; false: decrement immediately

Field Documentation

lpit_timer_modes_t _lpit_chnl_params::timerMode

lpit_trigger_source_t _lpit_chnl_params::triggerSource

struct _lpit_config

This structure holds the configuration settings for the LPIT peripheral. To initialize this structure to reasonable defaults, call the LPIT_GetDefaultConfig() function and pass a pointer to the configuration structure instance.

The configuration structure can be made constant so as to reside in flash.

Data Fields
bool	enableRunInDebug
	true: Timers run in debug mode; false: Timers stop in debug mode

bool	enableRunInDoze
	true: Timers run in doze mode; false: Timers stop in doze mode

Typedef Documentation

typedef enum _lpit_chnl lpit_chnl_t

Note: Actual number of available channels is SoC-dependent

typedef enum _lpit_timer_modes lpit_timer_modes_t

typedef enum _lpit_trigger_select lpit_trigger_select_t

This is used for both internal and external trigger sources. The actual trigger options available is SoC-specific, user should refer to the reference manual.

typedef enum _lpit_interrupt_enable lpit_interrupt_enable_t

Note: Number of timer channels are SoC-specific. See the SoC Reference Manual.

typedef enum _lpit_status_flags lpit_status_flags_t

Note: Number of timer channels are SoC-specific. See the SoC Reference Manual.

typedef struct _lpit_chnl_params lpit_chnl_params_t

typedef struct _lpit_config lpit_config_t

This structure holds the configuration settings for the LPIT peripheral. To initialize this structure to reasonable defaults, call the LPIT_GetDefaultConfig() function and pass a pointer to the configuration structure instance.

The configuration structure can be made constant so as to reside in flash.

Enumeration Type Documentation

enum _lpit_chnl

Note: Actual number of available channels is SoC-dependent

Enumerator
kLPIT_Chnl_0	LPIT channel number 0.
kLPIT_Chnl_1	LPIT channel number 1.
kLPIT_Chnl_2	LPIT channel number 2.
kLPIT_Chnl_3	LPIT channel number 3.

enum _lpit_timer_modes

Enumerator
kLPIT_PeriodicCounter	Use the all 32-bits, counter loads and decrements to zero.
kLPIT_DualPeriodicCounter	Counter loads, lower 16-bits decrement to zero, then upper 16-bits decrement.
kLPIT_TriggerAccumulator	Counter loads on first trigger and decrements on each trigger.
kLPIT_InputCapture	Counter loads with 0xFFFFFFFF, decrements to zero. It stores the inverse of the current value when a input trigger is detected

enum _lpit_trigger_select

This is used for both internal and external trigger sources. The actual trigger options available is SoC-specific, user should refer to the reference manual.

Enumerator
kLPIT_Trigger_TimerChn0	Channel 0 is selected as a trigger source.
kLPIT_Trigger_TimerChn1	Channel 1 is selected as a trigger source.
kLPIT_Trigger_TimerChn2	Channel 2 is selected as a trigger source.
kLPIT_Trigger_TimerChn3	Channel 3 is selected as a trigger source.
kLPIT_Trigger_TimerChn4	Channel 4 is selected as a trigger source.
kLPIT_Trigger_TimerChn5	Channel 5 is selected as a trigger source.
kLPIT_Trigger_TimerChn6	Channel 6 is selected as a trigger source.
kLPIT_Trigger_TimerChn7	Channel 7 is selected as a trigger source.
kLPIT_Trigger_TimerChn8	Channel 8 is selected as a trigger source.
kLPIT_Trigger_TimerChn9	Channel 9 is selected as a trigger source.
kLPIT_Trigger_TimerChn10	Channel 10 is selected as a trigger source.
kLPIT_Trigger_TimerChn11	Channel 11 is selected as a trigger source.
kLPIT_Trigger_TimerChn12	Channel 12 is selected as a trigger source.
kLPIT_Trigger_TimerChn13	Channel 13 is selected as a trigger source.
kLPIT_Trigger_TimerChn14	Channel 14 is selected as a trigger source.
kLPIT_Trigger_TimerChn15	Channel 15 is selected as a trigger source.

enum _lpit_trigger_source

Enumerator
kLPIT_TriggerSource_External	Use external trigger input.
kLPIT_TriggerSource_Internal	Use internal trigger.

enum _lpit_interrupt_enable

Note: Number of timer channels are SoC-specific. See the SoC Reference Manual.

Enumerator
kLPIT_Channel0TimerInterruptEnable	Channel 0 Timer interrupt.
kLPIT_Channel1TimerInterruptEnable	Channel 1 Timer interrupt.
kLPIT_Channel2TimerInterruptEnable	Channel 2 Timer interrupt.
kLPIT_Channel3TimerInterruptEnable	Channel 3 Timer interrupt.

enum _lpit_status_flags

Note: Number of timer channels are SoC-specific. See the SoC Reference Manual.

Enumerator
kLPIT_Channel0TimerFlag	Channel 0 Timer interrupt flag.
kLPIT_Channel1TimerFlag	Channel 1 Timer interrupt flag.
kLPIT_Channel2TimerFlag	Channel 2 Timer interrupt flag.
kLPIT_Channel3TimerFlag	Channel 3 Timer interrupt flag.

Function Documentation

void LPIT_Init	(	LPIT_Type *	base,
		const lpit_config_t *	config
	)

This function issues a software reset to reset all channels and registers except the Module Control register.

Note: This API should be called at the beginning of the application using the LPIT driver.

Parameters

base	LPIT peripheral base address.
config	Pointer to the user configuration structure.

void LPIT_Deinit ( LPIT_Type * base )

Parameters

base	LPIT peripheral base address.

void LPIT_GetDefaultConfig ( lpit_config_t * config )

The default values are:

*    config->enableRunInDebug = false;
*    config->enableRunInDoze = false;
* 

Parameters

config Pointer to the user configuration structure.

status_t LPIT_SetupChannel	(	LPIT_Type *	base,
		lpit_chnl_t	channel,
		const lpit_chnl_params_t *	chnlSetup
	)

This function sets up the operation mode to one of the options available in the enumeration lpit_timer_modes_t. It sets the trigger source as either internal or external, trigger selection and the timers behaviour when a timeout occurs. It also chains the timer if a prior timer if requested by the user.

Parameters

base	LPIT peripheral base address.
channel	Channel that is being configured.
chnlSetup	Configuration parameters.

static void LPIT_EnableInterrupts	(	LPIT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	LPIT peripheral base address.
mask	The interrupts to enable. This is a logical OR of members of the enumeration lpit_interrupt_enable_t

static void LPIT_DisableInterrupts	(	LPIT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	LPIT peripheral base address.
mask	The interrupts to enable. This is a logical OR of members of the enumeration lpit_interrupt_enable_t

static uint32_t LPIT_GetEnabledInterrupts ( LPIT_Type * base )

inlinestatic

Parameters

base	LPIT peripheral base address.

Returns: The enabled interrupts. This is the logical OR of members of the enumeration lpit_interrupt_enable_t

static uint32_t LPIT_GetStatusFlags ( LPIT_Type * base )

inlinestatic

Parameters

base	LPIT peripheral base address.

Returns: The status flags. This is the logical OR of members of the enumeration lpit_status_flags_t

static void LPIT_ClearStatusFlags	(	LPIT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	LPIT peripheral base address.
mask	The status flags to clear. This is a logical OR of members of the enumeration lpit_status_flags_t

static void LPIT_SetTimerPeriod	(	LPIT_Type *	base,
		lpit_chnl_t	channel,
		uint32_t	ticks
	)

inlinestatic

Timers begin counting down from the value set by this function until it reaches 0, at which point it generates an interrupt and loads this register value again. Writing a new value to this register does not restart the timer. Instead, the value is loaded after the timer expires.

Note: User can call the utility macros provided in fsl_common.h to convert to ticks.

Parameters

base	LPIT peripheral base address.
channel	Timer channel number.
ticks	Timer period in units of ticks.

static void LPIT_SetTimerValue	(	LPIT_Type *	base,
		lpit_chnl_t	channel,
		uint32_t	ticks
	)

inlinestatic

In the Dual 16-bit Periodic Counter mode, the counter will load and then the lower 16-bits will decrement down to zero, which will assert the output pre-trigger. The upper 16-bits will then decrement down to zero, which will negate the output pre-trigger and set the timer interrupt flag.

Note: Set TVAL register to 0 or 1 is invalid in compare mode.

Parameters

base	LPIT peripheral base address.
channel	Timer channel number.
ticks	Timer period in units of ticks.

static uint32_t LPIT_GetCurrentTimerCount	(	LPIT_Type *	base,
		lpit_chnl_t	channel
	)

inlinestatic

This function returns the real-time timer counting value, in a range from 0 to a timer period.

Note: User can call the utility macros provided in fsl_common.h to convert ticks to microseconds or milliseconds.

Parameters

base	LPIT peripheral base address.
channel	Timer channel number.

Returns: Current timer counting value in ticks.

static void LPIT_StartTimer	(	LPIT_Type *	base,
		lpit_chnl_t	channel
	)

inlinestatic

After calling this function, timers load the period value and count down to 0. When the timer reaches 0, it generates a trigger pulse and sets the timeout interrupt flag.

Parameters

base	LPIT peripheral base address.
channel	Timer channel number.

static void LPIT_StopTimer	(	LPIT_Type *	base,
		lpit_chnl_t	channel
	)

inlinestatic

Parameters

base	LPIT peripheral base address.
channel	Timer channel number.

static void LPIT_Reset ( LPIT_Type * base )

inlinestatic

This resets all channels and registers except the Module Control Register.

Parameters

base	LPIT peripheral base address.

Overview

Function groups

Initialization and deinitialization

Timer period Operations

Start and Stop timer operations

Status

Interrupt

Typical use case

LPIT tick example

Data Structures

Functions

Driver version

Initialization and deinitialization

Interrupt Interface

Status Interface

Read and Write the timer period

Timer Start and Stop

Data Structure Documentation

Data Fields

Field Documentation

Data Fields

Typedef Documentation

Enumeration Type Documentation

Function Documentation