Overview

The MCUXpresso SDK provides a driver for the Pulse Width Timer (PWT) of MCUXpresso SDK devices.

Function groups

The PWT driver supports capture or measure the pulse width mapping on its input channels. The counter of PWT has two selectable clock sources, Timer clock and alternative clock. PWT module supports programmable positive or negative pulse edges, and programmable interrupt generation upon pulse width values or counter overflow.

Initialization and deinitialization

The function PWT_Init() initializes the PWT with specified configurations. The function PWT_GetDefaultConfig() gets the default configurations. The initialization function configures the PWT for the requested register update mode for register with buffers.

The function PWT_Deinit() disables the PWT counter and turns off the module clock.

Reset

The function PWT_Reset() is built into PWT as a mechanism used to reset/restart the pulse width timer.

Status

Provides functions to get and clear the PWT status.

Interrupt

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

Start & Stop timer

The function PWT_StartTimer() starts the PWT time counter.

The function PWT_StopTimer() stops the PWT time counter.

GetInterrupt

Provides functions to generate Overflow/Pulse Width Data Ready Interrupt.

Get Timer value

The function PWT_GetCurrentTimerCount() is set to read the current counter value.

The function PWT_ReadPositivePulseWidth() is set to read the positive pulse width.

The function PWT_ReadNegativePulseWidth() is set to read the negative pulse width.

PWT Operations

Input capture operations

The input capture operations sets up an channel for input capture.

The function EdgeCapture can be used to measure the pulse width of a signal. A channel is used during capture with the input signal coming through a channel n. The capture edge for each channel, and any filter value to be used when processing the input signal.

Typical use case

PWT measure

This is an example code to measure the pulse width:

Refer to the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/pwt

Data Structures
struct	pwt_config_t
	PWT configuration structure. More...

Macros
#define	FSL_PWT_DRIVER_VERSION (MAKE_VERSION(2, 0, 1))
	Version 2.0.1.

Enumerations
enum	pwt_clock_source_t { kPWT_TimerClock = 0U, kPWT_AlternativeClock }
	PWT clock source selection. More...

enum	pwt_clock_prescale_t { kPWT_Prescale_Divide_1 = 0U, kPWT_Prescale_Divide_2, kPWT_Prescale_Divide_4, kPWT_Prescale_Divide_8, kPWT_Prescale_Divide_16, kPWT_Prescale_Divide_32, kPWT_Prescale_Divide_64, kPWT_Prescale_Divide_128 }
	PWT prescaler factor selection for clock source. More...

enum	pwt_input_edge_t { kPWT_StartFall_CaptureFall_Edge = 0U, kPWT_StartRise_CaptureRiseAndFall_Edge, kPWT_StartFall_CaptureRiseAndFall_Edge, kPWT_StartRise_CaptureRise_Edge }
	PWT Input Edge. More...

enum	pwt_input_select_t { kPWT_InputPort_0 = 0U, kPWT_InputPort_1, kPWT_InputPort_2, kPWT_InputPort_3 }
	PWT input port selection. More...

enum	pwt_interrupt_enable_t { kPWT_ModuleInterruptEnable = PWT_R1_PWTIE_MASK, kPWT_PulseWidthReadyInterruptEnable = PWT_R1_PRDYIE_MASK, kPWT_CounterOverflowInterruptEnable = PWT_R1_POVIE_MASK }
	List of PWT interrupts. More...

enum	pwt_status_flags_t { kPWT_CounterOverflowFlag = PWT_R1_PWTOV_MASK, kPWT_PulseWidthValidFlag = PWT_R1_PWTRDY_MASK }
	List of PWT flags. More...

Functions
static uint16_t	PWT_GetCurrentTimerCount (PWT_Type *base)
	Reads the current counter value. More...

static uint16_t	PWT_ReadPositivePulseWidth (PWT_Type *base)
	Reads the positive pulse width. More...

static uint16_t	PWT_ReadNegativePulseWidth (PWT_Type *base)
	Reads the negative pulse width. More...

static void	PWT_Reset (PWT_Type *base)
	Performs a software reset on the PWT module. More...

Initialization and deinitialization
void	PWT_Init (PWT_Type base, const pwt_config_t config)
	Ungates the PWT clock and configures the peripheral for basic operation. More...

void	PWT_Deinit (PWT_Type *base)
	Gates the PWT clock. More...

void	PWT_GetDefaultConfig (pwt_config_t *config)
	Fills in the PWT configuration structure with the default settings. More...

Interrupt Interface
static void	PWT_EnableInterrupts (PWT_Type *base, uint32_t mask)
	Enables the selected PWT interrupts. More...

static void	PWT_DisableInterrupts (PWT_Type *base, uint32_t mask)
	Disables the selected PWT interrupts. More...

static uint32_t	PWT_GetEnabledInterrupts (PWT_Type *base)
	Gets the enabled PWT interrupts. More...

Status Interface
static uint32_t	PWT_GetStatusFlags (PWT_Type *base)
	Gets the PWT status flags. More...

static void	PWT_ClearStatusFlags (PWT_Type *base, uint32_t mask)
	Clears the PWT status flags. More...

Timer Start and Stop
static void	PWT_StartTimer (PWT_Type *base)
	Starts the PWT counter. More...

static void	PWT_StopTimer (PWT_Type *base)
	Stops the PWT counter. More...

Data Structure Documentation

struct pwt_config_t

This structure holds the configuration settings for the PWT peripheral. To initialize this structure to reasonable defaults, call the PWT_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
pwt_clock_source_t	clockSource
	Clock source for the counter.

pwt_clock_prescale_t	prescale
	Pre-scaler to divide down the clock.

pwt_input_select_t	inputSelect
	PWT Pulse input port selection.

pwt_input_edge_t	edge
	PWT Input Edge.

Enumeration Type Documentation

enum pwt_clock_source_t

Enumerator
kPWT_TimerClock	The Timer clock is used as the clock source of PWT counter.
kPWT_AlternativeClock	Alternative clock is used as the clock source of PWT counter.

enum pwt_clock_prescale_t

Enumerator
kPWT_Prescale_Divide_1	PWT clock divided by 1.
kPWT_Prescale_Divide_2	PWT clock divided by 2.
kPWT_Prescale_Divide_4	PWT clock divided by 4.
kPWT_Prescale_Divide_8	PWT clock divided by 8.
kPWT_Prescale_Divide_16	PWT clock divided by 16.
kPWT_Prescale_Divide_32	PWT clock divided by 32.
kPWT_Prescale_Divide_64	PWT clock divided by 64.
kPWT_Prescale_Divide_128	PWT clock divided by 128.

enum pwt_input_edge_t

Enumerator
kPWT_StartFall_CaptureFall_Edge	The first falling-edge starts the pulse width measurement, and on all the subsequent falling edges, the pulse width is captured.
kPWT_StartRise_CaptureRiseAndFall_Edge	The first rising edge starts the pulse width measurement, and on all the subsequent rising and falling edges, the pulse width is captured.
kPWT_StartFall_CaptureRiseAndFall_Edge	The first falling edge starts the pulse width measurement, and on all the subsequent rising and falling edges, the pulse width is captured.
kPWT_StartRise_CaptureRise_Edge	The first-rising edge starts the pulse width measurement, and on all the subsequent rising edges, the pulse width is captured.

enum pwt_input_select_t

Enumerator
kPWT_InputPort_0	PWT input comes from PWTIN[0].
kPWT_InputPort_1	PWT input comes from PWTIN[1].
kPWT_InputPort_2	PWT input comes from PWTIN[2].
kPWT_InputPort_3	PWT input comes from PWTIN[3].

enum pwt_interrupt_enable_t

Enumerator
kPWT_ModuleInterruptEnable	Module Interrupt.
kPWT_PulseWidthReadyInterruptEnable	Pulse width data ready interrupt.
kPWT_CounterOverflowInterruptEnable	Counter overflow interrupt.

enum pwt_status_flags_t

Enumerator
kPWT_CounterOverflowFlag	Counter overflow flag.
kPWT_PulseWidthValidFlag	Pulse width valid flag.

Function Documentation

void PWT_Init	(	PWT_Type *	base,
		const pwt_config_t *	config
	)

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

Parameters

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

void PWT_Deinit ( PWT_Type * base )

Parameters

base	PWT peripheral base address

void PWT_GetDefaultConfig ( pwt_config_t * config )

The default values are:

*   config->clockSource = kPWT_TimerClock;
*   config->prescale = kPWT_Prescale_Divide_1;
*   config->inputSelect = kPWT_InputPort_0;
*   config->edge = kPWT_StartRise_CaptureRiseAndFall_Edge;
* 

Parameters

config Pointer to the user configuration structure.

static void PWT_EnableInterrupts	(	PWT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

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

static void PWT_DisableInterrupts	(	PWT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

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

static uint32_t PWT_GetEnabledInterrupts ( PWT_Type * base )

inlinestatic

Parameters

base	PWT peripheral base address

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

static uint32_t PWT_GetStatusFlags ( PWT_Type * base )

inlinestatic

Parameters

base	PWT peripheral base address

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

static void PWT_ClearStatusFlags	(	PWT_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

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

static void PWT_StartTimer ( PWT_Type * base )

inlinestatic

Parameters

base	PWT peripheral base address

static void PWT_StopTimer ( PWT_Type * base )

inlinestatic

Parameters

base	PWT peripheral base address

static uint16_t PWT_GetCurrentTimerCount ( PWT_Type * base )

inlinestatic

This function returns the timer counting value

Parameters

base	PWT peripheral base address

Returns: Current 16-bit timer counter value

static uint16_t PWT_ReadPositivePulseWidth ( PWT_Type * base )

inlinestatic

This function reads the low and high registers and returns the 16-bit positive pulse width

Parameters

base	PWT peripheral base address.

Returns: The 16-bit positive pulse width.

static uint16_t PWT_ReadNegativePulseWidth ( PWT_Type * base )

inlinestatic

This function reads the low and high registers and returns the 16-bit negative pulse width

Parameters

base	PWT peripheral base address.

Returns: The 16-bit negative pulse width.

static void PWT_Reset ( PWT_Type * base )

inlinestatic

Parameters

base	PWT peripheral base address

Overview

Function groups

Initialization and deinitialization

Reset

Status

Interrupt

Start & Stop timer

GetInterrupt

Get Timer value

PWT Operations

Input capture operations

Typical use case

PWT measure

Data Structures

Macros

Enumerations

Functions

Initialization and deinitialization

Interrupt Interface

Status Interface

Timer Start and Stop

Data Structure Documentation

Data Fields

Enumeration Type Documentation

Function Documentation