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.

int main(void)
{
    /* Structure of initialize LPIT */
    lpit_config_t lpitConfig;
    lpit_chnl_params_t lpitChannelConfig;
    /* Initialize and enable LED */
    LED_Init();
    /* Board pin, clock, debug console init */
    BOARD_InitHardware();
    LPIT_GetDefaultConfig(&lpitConfig);
    /* Init lpit module */
    LPIT_Init(LPIT0, &lpitConfig);
    lpitChannelConfig.chainChannel = false;
    lpitChannelConfig.enableReloadOnTrigger = false;
    lpitChannelConfig.enableStartOnTrigger = false;
    lpitChannelConfig.enableStopOnTimeout = false;
    lpitChannelConfig.timerMode = kLPIT_PeriodicCounter;
    /* Set default values for the trigger source */
    lpitChannelConfig.triggerSelect = kLPIT_Trigger_TimerChn0;
    lpitChannelConfig.triggerSource = kLPIT_TriggerSource_External;
    /* Init lpit channel 0 */
    LPIT_SetupChannel(LPIT0, kLPIT_Chnl_0, &lpitChannelConfig);
    /* Set timer period for channel 0 */
    LPIT_SetTimerPeriod(LPIT0, kLPIT_Chnl_0, USEC_TO_COUNT(1000000U, LPIT_SOURCECLOCK));
    /* Enable timer interrupts for channel 0 */
    LPIT_EnableInterrupts(LPIT0, kLPIT_Channel0TimerInterruptEnable);
    /* Enable at the NVIC */
    EnableIRQ(LPIT0_IRQn);
    /* Start channel 0 */
    PRINTF("\r\nStarting channel No.0 ...");
    LPIT_StartTimer(LPIT0, kLPIT_Chnl_0);
    while (true)
    {
        /* Check whether occur interupt and toggle LED */
        if (true == lpitIsrFlag)
        {
            PRINTF("\r\n Channel No.0 interrupt is occured !");
            LED_Toggle();
            lpitIsrFlag = false;
        }
    }
}

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

struct	lpit_config_t
	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_t { kLPIT_Chnl_0 = 0U, kLPIT_Chnl_1, kLPIT_Chnl_2, kLPIT_Chnl_3 }
	List of LPIT channels. More...

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

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

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

#define	FSL_LPIT_DRIVER_VERSION (MAKE_VERSION(2, 0, 0))
	Version 2.0.0.

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 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_t

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_t::timerMode

lpit_trigger_source_t lpit_chnl_params_t::triggerSource

struct 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.

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

Enumeration Type Documentation

enum lpit_chnl_t

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_t

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_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.

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_t

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

enum lpit_interrupt_enable_t

Note: Number of timer channels are SoC-specific. See the Kinetis 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_t

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

Enumeration Type Documentation

Function Documentation