Description

Non-blocking software timers that have to be polled to determine if they have expired.

File(s):

These timers are suitable for applications that are not timing critical. A global counter is incremented with each clock tick and this value is polled to determine if a timer has expired. Provision is made for counter roll-over.

This module depends on a system clock module, e.g. px_sysclk.h : System Clock using a TMRx peripheral to return a counter that is incremented with every system clock tick. The number of ticks per second (Hz) is defined with PX_SYSTMR_TICKS_PER_SEC.

Example:

#include "px_sysclk.h"
#include "px_systmr.h"
#include "px_compiler.h"
 
void px_systmr_test(void)
{
    // Create a timer object
    px_systmr_t tmr;
 
    // Initialise module
    px_sysclk_init();
 
    // Enable interrupts
    px_interrupts_enable();
  
    // Start timer with a 250 ms timeout
    px_systmr_start(&tmr, TMR_MS_TO_TICKS(250));
    
    // Loop forever
    while(true)
    {
        // Wait until timer has expired
        while(!px_systmr_has_expired(&tmr))
        {
            ;
        }
 
        // Restart timer
        px_systmr_restart(&tmr);
        
        // Do someting...
    }
}

Data Structures
struct	px_systmr_t
	Structure to track state of a timer. More...

Macros
#define	PX_SYSTMR_TICKS_PER_SEC PX_SYSCLK_CFG_TICKS_PER_SEC
	The number of timer ticks per second. More...

#define	PX_SYSTMR_MS_TO_TICKS(delay_in_ms) PX_UDIV_ROUND((delay_in_ms) * PX_SYSTMR_TICKS_PER_SEC, 1000ul)
	Macro used to convert a timeout in milliseconds to timer ticks. More...

Typedefs
typedef px_sysclk_ticks_t	px_systmr_ticks_t
	Size definition of the tick counter. More...

Enumerations
enum	px_systmr_state_t
	Timer state. More...

Functions
void	px_systmr_start (px_systmr_t *systmr, const px_systmr_ticks_t delay_in_ticks)
	Start a timer. More...

bool	px_systmr_has_started (const px_systmr_t *systmr)
	See if a timer has been started. More...

bool	px_systmr_has_expired (px_systmr_t *systmr)
	See if a timer has expired. More...

void	px_systmr_stop (px_systmr_t *systmr)
	Stop a running timer. More...

void	px_systmr_restart (px_systmr_t *systmr)
	Restart a timer with the delay set with px_systmr_start(). More...

void	px_systmr_reset (px_systmr_t *systmr)
	Reset a timer with the delay set with px_systmr_start(). More...

void	px_systmr_wait (const px_systmr_ticks_t delay_in_ticks)
	Blocking wait for specified number of ticks. More...

px_systmr_ticks_t	px_systmr_ticks_elapsed (px_systmr_t *systmr)
	Return the number of ticks that have elapsed sinced the timer has been started. More...

Data Structure Documentation

◆ px_systmr_t

struct px_systmr_t

Structure to track state of a timer.

Definition at line 74 of file px_systmr.h.

Data Fields
px_systmr_state_t	state	State of timer: STOPPED, STARTED or EXPIRED.
px_systmr_ticks_t	start_tick	Tick when timer started.
px_systmr_ticks_t	delay_in_ticks	Timer delay, used for subsequent timer restarts/resets.

Macro Definition Documentation

◆ PX_SYSTMR_TICKS_PER_SEC

#define PX_SYSTMR_TICKS_PER_SEC PX_SYSCLK_CFG_TICKS_PER_SEC

The number of timer ticks per second.

Definition at line 59 of file px_systmr.h.

◆ PX_SYSTMR_MS_TO_TICKS

#define PX_SYSTMR_MS_TO_TICKS ( delay_in_ms ) PX_UDIV_ROUND((delay_in_ms) * PX_SYSTMR_TICKS_PER_SEC, 1000ul)

Macro used to convert a timeout in milliseconds to timer ticks.

Parameters

[in] delay_in_ms Delay in milliseconds

Returns: Delay in timer ticks

Definition at line 177 of file px_systmr.h.

Typedef Documentation

◆ px_systmr_ticks_t

typedef px_sysclk_ticks_t px_systmr_ticks_t

Size definition of the tick counter.

Definition at line 63 of file px_systmr.h.

Enumeration Type Documentation

◆ px_systmr_state_t

enum px_systmr_state_t

Timer state.

Definition at line 66 of file px_systmr.h.

Function Documentation

◆ px_systmr_start()

void px_systmr_start	(	px_systmr_t *	systmr,
		const px_systmr_ticks_t	delay_in_ticks
	)

Start a timer.

Parameters

[in,out]	systmr	Pointer to a timer object
[in]	delay_in_ticks	Delay in timer ticks

Definition at line 35 of file px_systmr.c.

◆ px_systmr_has_started()

bool px_systmr_has_started ( const px_systmr_t * systmr )

See if a timer has been started.

Parameters

[in] systmr Pointer to a timer object

Return values

true	timer started
false	timer stopped or expired

Definition at line 45 of file px_systmr.c.

◆ px_systmr_has_expired()

bool px_systmr_has_expired ( px_systmr_t * systmr )

See if a timer has expired.

Parameters

[in,out] systmr Pointer to a timer object

Return values

true	timer expired
false	timer not expired or timer stopped

Definition at line 57 of file px_systmr.c.

◆ px_systmr_stop()

void px_systmr_stop ( px_systmr_t * systmr )

Stop a running timer.

Parameters

[in,out] systmr Pointer to a timer object

Definition at line 103 of file px_systmr.c.

◆ px_systmr_restart()

void px_systmr_restart ( px_systmr_t * systmr )

Restart a timer with the delay set with px_systmr_start().

The timer will expire from the current timer tick + systmr->delay_in_ticks.

Parameters

[in,out] systmr Pointer to a timer object

Definition at line 109 of file px_systmr.c.

◆ px_systmr_reset()

void px_systmr_reset ( px_systmr_t * systmr )

Reset a timer with the delay set with px_systmr_start().

The timer will expire on systmr->start_tick + systmr->delay_in_ticks.

Use this function instead of px_systmr_restart() for periodic timers, because the frequency will not drift over time. An error may accumulate if there is a delay between px_systmr_has_expired() and px_systmr_restart(). Thus the prefered usage for a periodic timer is:

while(true)
{
    // Wait until timer has expired
    while(px_systmr_has_expired(&systmr) == false)
    {
        ;
    }
    // Reset periodic timer
    px_systmr_reset(&systmr);
    // Do something...
}

Parameters

[in,out] systmr Pointer to a timer object

Definition at line 117 of file px_systmr.c.

◆ px_systmr_wait()

void px_systmr_wait ( const px_systmr_ticks_t delay_in_ticks )

Blocking wait for specified number of ticks.

Parameters

[in] delay_in_ticks Delay in timer ticks

Definition at line 125 of file px_systmr.c.

◆ px_systmr_ticks_elapsed()

px_systmr_ticks_t px_systmr_ticks_elapsed ( px_systmr_t * systmr )

Return the number of ticks that have elapsed sinced the timer has been started.

Parameters

[in,out] systmr Pointer to a timer object

Returns: px_systmr_ticks_t Number of ticks elapsed

Definition at line 135 of file px_systmr.c.

Description

Data Structures

Macros

Typedefs

Enumerations

Functions

Data Structure Documentation

◆ px_systmr_t

Macro Definition Documentation

◆ PX_SYSTMR_TICKS_PER_SEC

◆ PX_SYSTMR_MS_TO_TICKS

Typedef Documentation

◆ px_systmr_ticks_t

Enumeration Type Documentation

◆ px_systmr_state_t

Function Documentation

◆ px_systmr_start()

◆ px_systmr_has_started()

◆ px_systmr_has_expired()

◆ px_systmr_stop()

◆ px_systmr_restart()

◆ px_systmr_reset()

◆ px_systmr_wait()

◆ px_systmr_ticks_elapsed()