Overview

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

Function groups

The LPTMR driver supports operating the module as a time counter or as a pulse counter.

Initialization and deinitialization

The function LPTMR_Init() initializes the LPTMR with specified configurations. The function LPTMR_GetDefaultConfig() gets the default configurations. The initialization function configures the LPTMR for a timer or a pulse counter mode mode. It also sets up the LPTMR's free running mode operation and a clock source.

The function LPTMR_DeInit() disables the LPTMR module and gates the module clock.

Timer period Operations

The function LPTMR_SetTimerPeriod() sets the timer period in units of count. Timers counts from 0 to the count value set here.

The function LPTMR_GetCurrentTimerCount() reads the current timer counting value. This function returns the real-time timer counting value ranging from 0 to a timer period.

The timer period operation function takes the count value in ticks. Call the utility macros provided in the fsl_common.h file to convert to microseconds or milliseconds.

Start and Stop timer operations

The function LPTMR_StartTimer() starts the timer counting. After calling this function, the timer counts up to the counter value set earlier by using the LPTMR_SetPeriod() function. Each time the timer reaches the count value and increments, it generates a trigger pulse and sets the timeout interrupt flag. An interrupt is also triggered if the timer interrupt is enabled.

The function LPTMR_StopTimer() stops the timer counting and resets the timer's counter register.

Status

Provides functions to get and clear the LPTMR status.

Interrupt

Provides functions to enable/disable LPTMR interrupts and get the currently enabled interrupts.

Typical use case

LPTMR tick example

Updates the LPTMR period and toggles an LED periodically.

int main(void)
{
    uint32_t currentCounter = 0U;
    lptmr_config_t lptmrConfig;
    LED_INIT();
    /* Board pin, clock, debug console initialization */
    BOARD_InitHardware();
    /* Configures the LPTMR */
    LPTMR_GetDefaultConfig(&lptmrConfig);
    /* Initializes the LPTMR */
    LPTMR_Init(LPTMR0, &lptmrConfig);
    /* Sets the timer period */
    LPTMR_SetTimerPeriod(LPTMR0, USEC_TO_COUNT(1000000U, LPTMR_SOURCE_CLOCK));
    /* Enables a timer interrupt */
    LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
    /* Enables the NVIC */
    EnableIRQ(LPTMR0_IRQn);
    PRINTF("Low Power Timer Example\r\n");
    /* Starts counting */
    LPTMR_StartTimer(LPTMR0);
    while (1)
    {
        if (currentCounter != lptmrCounter)
        {
            currentCounter = lptmrCounter;
            PRINTF("LPTMR interrupt No.%d \r\n", currentCounter);
        }
    }
}

Data Structures
struct	lptmr_config_t
	LPTMR config structure. More...

Enumerations
enum	lptmr_pin_select_t { kLPTMR_PinSelectInput_0 = 0x0U, kLPTMR_PinSelectInput_1 = 0x1U, kLPTMR_PinSelectInput_2 = 0x2U, kLPTMR_PinSelectInput_3 = 0x3U }
	LPTMR pin selection used in pulse counter mode. More...

enum	lptmr_pin_polarity_t { kLPTMR_PinPolarityActiveHigh = 0x0U, kLPTMR_PinPolarityActiveLow = 0x1U }
	LPTMR pin polarity used in pulse counter mode. More...

enum	lptmr_timer_mode_t { kLPTMR_TimerModeTimeCounter = 0x0U, kLPTMR_TimerModePulseCounter = 0x1U }
	LPTMR timer mode selection. More...

enum	lptmr_prescaler_glitch_value_t { kLPTMR_Prescale_Glitch_0 = 0x0U, kLPTMR_Prescale_Glitch_1 = 0x1U, kLPTMR_Prescale_Glitch_2 = 0x2U, kLPTMR_Prescale_Glitch_3 = 0x3U, kLPTMR_Prescale_Glitch_4 = 0x4U, kLPTMR_Prescale_Glitch_5 = 0x5U, kLPTMR_Prescale_Glitch_6 = 0x6U, kLPTMR_Prescale_Glitch_7 = 0x7U, kLPTMR_Prescale_Glitch_8 = 0x8U, kLPTMR_Prescale_Glitch_9 = 0x9U, kLPTMR_Prescale_Glitch_10 = 0xAU, kLPTMR_Prescale_Glitch_11 = 0xBU, kLPTMR_Prescale_Glitch_12 = 0xCU, kLPTMR_Prescale_Glitch_13 = 0xDU, kLPTMR_Prescale_Glitch_14 = 0xEU, kLPTMR_Prescale_Glitch_15 = 0xFU }
	LPTMR prescaler/glitch filter values. More...

enum	lptmr_prescaler_clock_select_t { kLPTMR_PrescalerClock_0 = 0x0U, kLPTMR_PrescalerClock_1 = 0x1U, kLPTMR_PrescalerClock_2 = 0x2U, kLPTMR_PrescalerClock_3 = 0x3U }
	LPTMR prescaler/glitch filter clock select. More...

enum	lptmr_interrupt_enable_t { kLPTMR_TimerInterruptEnable = LPTMR_CSR_TIE_MASK }
	List of the LPTMR interrupts. More...

enum	lptmr_status_flags_t { kLPTMR_TimerCompareFlag = LPTMR_CSR_TCF_MASK }
	List of the LPTMR status flags. More...

Driver version
#define	FSL_LPTMR_DRIVER_VERSION (MAKE_VERSION(2, 0, 1))
	Version 2.0.1.

Initialization and deinitialization
void	LPTMR_Init (LPTMR_Type base, const lptmr_config_t config)
	Ungates the LPTMR clock and configures the peripheral for a basic operation. More...

void	LPTMR_Deinit (LPTMR_Type *base)
	Gates the LPTMR clock. More...

void	LPTMR_GetDefaultConfig (lptmr_config_t *config)
	Fills in the LPTMR configuration structure with default settings. More...

Interrupt Interface
static void	LPTMR_EnableInterrupts (LPTMR_Type *base, uint32_t mask)
	Enables the selected LPTMR interrupts. More...

static void	LPTMR_DisableInterrupts (LPTMR_Type *base, uint32_t mask)
	Disables the selected LPTMR interrupts. More...

static uint32_t	LPTMR_GetEnabledInterrupts (LPTMR_Type *base)
	Gets the enabled LPTMR interrupts. More...

Status Interface
static uint32_t	LPTMR_GetStatusFlags (LPTMR_Type *base)
	Gets the LPTMR status flags. More...

static void	LPTMR_ClearStatusFlags (LPTMR_Type *base, uint32_t mask)
	Clears the LPTMR status flags. More...

Read and write the timer period
static void	LPTMR_SetTimerPeriod (LPTMR_Type *base, uint32_t ticks)
	Sets the timer period in units of count. More...

static uint32_t	LPTMR_GetCurrentTimerCount (LPTMR_Type *base)
	Reads the current timer counting value. More...

Timer Start and Stop
static void	LPTMR_StartTimer (LPTMR_Type *base)
	Starts the timer. More...

static void	LPTMR_StopTimer (LPTMR_Type *base)
	Stops the timer. More...

Data Structure Documentation

struct lptmr_config_t

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

The configuration struct can be made constant so it resides in flash.

Data Fields
lptmr_timer_mode_t	timerMode
	Time counter mode or pulse counter mode.

lptmr_pin_select_t	pinSelect
	LPTMR pulse input pin select; used only in pulse counter mode.

lptmr_pin_polarity_t	pinPolarity
	LPTMR pulse input pin polarity; used only in pulse counter mode.

bool	enableFreeRunning
	True: enable free running, counter is reset on overflow False: counter is reset when the compare flag is set.

bool	bypassPrescaler
	True: bypass prescaler; false: use clock from prescaler.

lptmr_prescaler_clock_select_t	prescalerClockSource
	LPTMR clock source.

lptmr_prescaler_glitch_value_t	value
	Prescaler or glitch filter value.

Enumeration Type Documentation

enum lptmr_pin_select_t

Enumerator
kLPTMR_PinSelectInput_0	Pulse counter input 0 is selected.
kLPTMR_PinSelectInput_1	Pulse counter input 1 is selected.
kLPTMR_PinSelectInput_2	Pulse counter input 2 is selected.
kLPTMR_PinSelectInput_3	Pulse counter input 3 is selected.

enum lptmr_pin_polarity_t

Enumerator
kLPTMR_PinPolarityActiveHigh	Pulse Counter input source is active-high.
kLPTMR_PinPolarityActiveLow	Pulse Counter input source is active-low.

enum lptmr_timer_mode_t

Enumerator
kLPTMR_TimerModeTimeCounter	Time Counter mode.
kLPTMR_TimerModePulseCounter	Pulse Counter mode.

enum lptmr_prescaler_glitch_value_t

Enumerator
kLPTMR_Prescale_Glitch_0	Prescaler divide 2, glitch filter does not support this setting.
kLPTMR_Prescale_Glitch_1	Prescaler divide 4, glitch filter 2.
kLPTMR_Prescale_Glitch_2	Prescaler divide 8, glitch filter 4.
kLPTMR_Prescale_Glitch_3	Prescaler divide 16, glitch filter 8.
kLPTMR_Prescale_Glitch_4	Prescaler divide 32, glitch filter 16.
kLPTMR_Prescale_Glitch_5	Prescaler divide 64, glitch filter 32.
kLPTMR_Prescale_Glitch_6	Prescaler divide 128, glitch filter 64.
kLPTMR_Prescale_Glitch_7	Prescaler divide 256, glitch filter 128.
kLPTMR_Prescale_Glitch_8	Prescaler divide 512, glitch filter 256.
kLPTMR_Prescale_Glitch_9	Prescaler divide 1024, glitch filter 512.
kLPTMR_Prescale_Glitch_10	Prescaler divide 2048 glitch filter 1024.
kLPTMR_Prescale_Glitch_11	Prescaler divide 4096, glitch filter 2048.
kLPTMR_Prescale_Glitch_12	Prescaler divide 8192, glitch filter 4096.
kLPTMR_Prescale_Glitch_13	Prescaler divide 16384, glitch filter 8192.
kLPTMR_Prescale_Glitch_14	Prescaler divide 32768, glitch filter 16384.
kLPTMR_Prescale_Glitch_15	Prescaler divide 65536, glitch filter 32768.

enum lptmr_prescaler_clock_select_t

Note: Clock connections are SoC-specific

Enumerator
kLPTMR_PrescalerClock_0	Prescaler/glitch filter clock 0 selected.
kLPTMR_PrescalerClock_1	Prescaler/glitch filter clock 1 selected.
kLPTMR_PrescalerClock_2	Prescaler/glitch filter clock 2 selected.
kLPTMR_PrescalerClock_3	Prescaler/glitch filter clock 3 selected.

enum lptmr_interrupt_enable_t

Enumerator
kLPTMR_TimerInterruptEnable	Timer interrupt enable.

enum lptmr_status_flags_t

Enumerator
kLPTMR_TimerCompareFlag	Timer compare flag.

Function Documentation

void LPTMR_Init	(	LPTMR_Type *	base,
		const lptmr_config_t *	config
	)

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

Parameters

base	LPTMR peripheral base address
config	A pointer to the LPTMR configuration structure.

void LPTMR_Deinit ( LPTMR_Type * base )

Parameters

base	LPTMR peripheral base address

void LPTMR_GetDefaultConfig ( lptmr_config_t * config )

The default values are as follows.

*    config->timerMode = kLPTMR_TimerModeTimeCounter;
*    config->pinSelect = kLPTMR_PinSelectInput_0;
*    config->pinPolarity = kLPTMR_PinPolarityActiveHigh;
*    config->enableFreeRunning = false;
*    config->bypassPrescaler = true;
*    config->prescalerClockSource = kLPTMR_PrescalerClock_1;
*    config->value = kLPTMR_Prescale_Glitch_0;
* 

Parameters

config A pointer to the LPTMR configuration structure.

static void LPTMR_EnableInterrupts	(	LPTMR_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

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

static void LPTMR_DisableInterrupts	(	LPTMR_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	LPTMR peripheral base address
mask	The interrupts to disable. This is a logical OR of members of the enumeration lptmr_interrupt_enable_t.

static uint32_t LPTMR_GetEnabledInterrupts ( LPTMR_Type * base )

inlinestatic

Parameters

base	LPTMR peripheral base address

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

static uint32_t LPTMR_GetStatusFlags ( LPTMR_Type * base )

inlinestatic

Parameters

base	LPTMR peripheral base address

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

static void LPTMR_ClearStatusFlags	(	LPTMR_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

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

static void LPTMR_SetTimerPeriod	(	LPTMR_Type *	base,
		uint32_t	ticks
	)

inlinestatic

Timers counts from 0 until it equals the count value set here. The count value is written to the CMR register.

Note

The TCF flag is set with the CNR equals the count provided here and then increments.
Call the utility macros provided in the fsl_common.h to convert to ticks.

Parameters

base	LPTMR peripheral base address
ticks	A timer period in units of ticks, which should be equal or greater than 1.

static uint32_t LPTMR_GetCurrentTimerCount ( LPTMR_Type * base )

inlinestatic

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

Note: Call the utility macros provided in the fsl_common.h to convert ticks to usec or msec.

Parameters

base	LPTMR peripheral base address

Returns: The current counter value in ticks

static void LPTMR_StartTimer ( LPTMR_Type * base )

inlinestatic

After calling this function, the timer counts up to the CMR register value. Each time the timer reaches the CMR value and then increments, it generates a trigger pulse and sets the timeout interrupt flag. An interrupt is also triggered if the timer interrupt is enabled.

Parameters

base	LPTMR peripheral base address

static void LPTMR_StopTimer ( LPTMR_Type * base )

inlinestatic

This function stops the timer and resets the timer's counter register.

Parameters

base	LPTMR peripheral base address

Overview

Function groups

Initialization and deinitialization

Timer period Operations

Start and Stop timer operations

Status

Interrupt

Typical use case

LPTMR tick example

Data Structures

Enumerations

Driver version

Initialization and deinitialization

Interrupt Interface

Status Interface

Read and write the timer period

Timer Start and Stop

Data Structure Documentation

Data Fields

Enumeration Type Documentation

Function Documentation