Header file with declarations and macros for systick utility. More...

#include <util/atomic.h>

Include dependency graph for systick.h:

This graph shows which files directly or indirectly include this file:

Data Structures
struct	SYSTICK_Timer_t
	Represents a SysTick software timer instance. More...

Typedefs
typedef enum SYSTICK_Timer_Status_t	SYSTICK_Timer_Status
	Alias for enum SYSTICK_Timer_Status_t representing SysTick timer states.
typedef struct SYSTICK_Timer_t	SYSTICK_Timer
	Alias for struct SYSTICK_Timer_t representing a SysTick software timer.

Enumerations
enum	SYSTICK_Timer_Status_t { SYSTICK_Timer_Running = 0 , SYSTICK_Timer_Expired }
	Represents the current status of the SysTick timer. More...

Functions
void	systick_init (void)
	Initializes the SysTick timer module.
void	systick_reset (void)
	Resets the SysTick timer value.
void	systick_tick (void)
	Increments the SysTick timer tick counter.
unsigned int	systick_current (void)
	Returns the current SysTick tick counter value.
void	systick_timer_set (SYSTICK_Timer *timer, unsigned int delay_ticks)
	Sets and starts a SysTick software timer.
SYSTICK_Timer_Status	systick_timer_elapsed (SYSTICK_Timer *timer)
	Checks whether a SysTick software timer has expired.
unsigned int	systick_timer_remaining (SYSTICK_Timer *timer)
	Returns the remaining time before a SysTick timer expires.
void	systick_timer_wait (unsigned int ticks)
	Blocks execution for a specified number of SysTick ticks.
void	systick_timer_wait_ms (unsigned int ms)
void	systick_timer_wait_us (unsigned int us)
void	systick_timer_cancel (SYSTICK_Timer *timer)
	Cancels a running SysTick software timer.

Detailed Description

Header file with declarations and macros for systick utility.

This file provides function prototypes, type definitions, and constants for handling systicks on systems.

Author: g.raf

Date: 2026-01-25

Version: 1.0 Release

Copyright: Copyright (c) 2025 g.raf Released under the GPLv3 License. (see LICENSE in repository)

Note: This file is part of a larger project and subject to the license specified in the repository. For updates and the complete revision history, see the GitHub repository.

See also: https://github.com/0x007e/utils-systick "Systick GitHub Repository"

Typedef Documentation

◆ SYSTICK_Timer

typedef struct SYSTICK_Timer_t SYSTICK_Timer

Alias for struct SYSTICK_Timer_t representing a SysTick software timer.

◆ SYSTICK_Timer_Status

typedef enum SYSTICK_Timer_Status_t SYSTICK_Timer_Status

Alias for enum SYSTICK_Timer_Status_t representing SysTick timer states.

Enumeration Type Documentation

◆ SYSTICK_Timer_Status_t

enum SYSTICK_Timer_Status_t

Represents the current status of the SysTick timer.

This enumeration defines the possible states of the SysTick timer. It indicates whether the timer is still counting down or if it has reached zero (expired).

Enumerator
SYSTICK_Timer_Running	Timer is currently running.
SYSTICK_Timer_Expired	Timer has expired.

Function Documentation

◆ systick_current()

unsigned int systick_current ( void )

Returns the current SysTick tick counter value.

This function reads the current value of the internal SysTick tick counter (systick_tick_value) in an atomic operation to prevent race conditions during concurrent access from interrupts. The returned value represents the elapsed system ticks since the last reset or initialization of the SysTick module.

Returns: The current SysTick tick counter value.

Note: The access is performed inside an ATOMIC_BLOCK to ensure data consistency when interrupts may update the tick value.

Here is the caller graph for this function:

◆ systick_init()

void systick_init ( void )

Initializes the SysTick timer module.

This function initializes the SysTick timer by resetting its internal state and preparing it for subsequent use. It calls systick_reset() to ensure the timer starts from a known default state.

Typically, this function should be called once during system initialization before any SysTick-based timing operations are performed.

Note: This function does not start the timer automatically; it only resets
and initializes the SysTick module.

Here is the call graph for this function:

◆ systick_reset()

void systick_reset ( void )

Resets the SysTick timer value.

This function clears the internal SysTick tick counter by setting systick_tick_value to zero. It ensures that the timer restarts counting from the beginning, which is useful during initialization or when restarting time measurements.

Note: This function does not alter the SysTick configuration or status. It only resets the tick counter value.

Here is the caller graph for this function:

◆ systick_tick()

void systick_tick ( void )

Increments the SysTick timer tick counter.

This function increases the internal systick_tick_value by one. It should be called periodically—typically from the SysTick interrupt service routine—to maintain an accurate system tick counter used for software timing and scheduling operations.

Note: This function must be invoked at a constant rate to ensure correct timekeeping for all SysTick-based timers.

◆ systick_timer_cancel()

void systick_timer_cancel ( SYSTICK_Timer * timer )

Cancels a running SysTick software timer.

This function stops a SysTick timer by setting its status to SYSTICK_Timer_Expired, effectively marking it as completed regardless of its current tick count. Once canceled, the timer will be considered expired and will no longer count down or trigger expiration checks.

Parameters

[in,out] timer Pointer to the SysTick timer instance to cancel.

Note: This function does not modify the timer’s expiration value; it only updates the status flag to indicate expiration.

◆ systick_timer_elapsed()

SYSTICK_Timer_Status systick_timer_elapsed ( SYSTICK_Timer * timer )

Checks whether a SysTick software timer has expired.

This function determines if the specified SYSTICK_Timer instance has reached its expiration tick value. If the current SysTick count has passed the timer's expire value, the timer status is updated to SYSTICK_Timer_Expired. Otherwise, the timer remains in the running state.

Parameters

[in,out] timer Pointer to the SysTick timer instance to check.

Returns

The current status of the timer:

SYSTICK_Timer_Running
SYSTICK_Timer_Expired

Note: The comparison uses signed arithmetic to handle counter wraparound
conditions correctly when the SysTick tick counter overflows.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ systick_timer_remaining()

unsigned int systick_timer_remaining ( SYSTICK_Timer * timer )

Returns the remaining time before a SysTick timer expires.

This function calculates the number of SysTick ticks remaining until the specified SYSTICK_Timer instance reaches its expiration value. If the timer has already expired, its status is updated to SYSTICK_Timer_Expired, and the function returns zero.

Parameters

[in,out] timer Pointer to the SysTick timer instance to query.

Returns: The number of SysTick ticks remaining until expiration, or 0 if the timer has already expired.

Note: The comparison uses signed arithmetic to correctly handle counter wraparound when the SysTick tick counter overflows.

Here is the call graph for this function:

◆ systick_timer_set()

void systick_timer_set	(	SYSTICK_Timer *	timer,
		unsigned int	delay_ticks )

Sets and starts a SysTick software timer.

This function initializes a given SYSTICK_Timer instance by setting its expiration tick value relative to the current SysTick count. The timer is configured to expire after the specified number of delay_ticks and marked as running.

Parameters

[in,out]	timer	Pointer to the SysTick timer instance to configure.
[in]	delay_ticks	Number of SysTick ticks after which the timer should expire.

Note: The timer must be periodically checked (e.g., via systick_timer_expired()) to determine when it has reached its expiration.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ systick_timer_wait()

void systick_timer_wait ( unsigned int ticks )

Blocks execution for a specified number of SysTick ticks.

This function creates a temporary SYSTICK_Timer instance and waits until it expires. The function blocks program execution by polling the timer status in a busy-wait loop, using a NOP instruction for each iteration to prevent compiler optimization and reduce power consumption on some architectures.

Parameters

[in] ticks The number of SysTick ticks to wait before returning.

Note: This is a blocking delay function and should only be used when precise timing is required, and multitasking is not critical. For non-blocking timing, use SYSTICK_Timer with periodic checks via systick_timer_elapsed() instead.

Here is the call graph for this function:

◆ systick_timer_wait_ms()

void systick_timer_wait_ms ( unsigned int ms )

Here is the caller graph for this function:

◆ systick_timer_wait_us()

void systick_timer_wait_us ( unsigned int us )

Data Structures

Typedefs

Enumerations

Functions

Detailed Description

Typedef Documentation

◆ SYSTICK_Timer

◆ SYSTICK_Timer_Status

Enumeration Type Documentation

◆ SYSTICK_Timer_Status_t

Function Documentation

◆ systick_current()

◆ systick_init()

◆ systick_reset()

◆ systick_tick()

◆ systick_timer_cancel()

◆ systick_timer_elapsed()

◆ systick_timer_remaining()

◆ systick_timer_set()

◆ systick_timer_wait()

◆ systick_timer_wait_ms()

◆ systick_timer_wait_us()