SysTick derived clock. More...

#include <cmsis-plus/rtos/os.h>

Inheritance diagram for os::rtos::clock_systick:

Public Types
Types & Constants
using	duration_t = port::clock::duration_t
	Type of variables holding clock durations.

using	timestamp_t = port::clock::timestamp_t
	Type of variables holding clock time stamps.

using	offset_t = port::clock::offset_t
	Type of variables holding clock offsets.

Public Member Functions
Constructors & Destructor
	clock_systick ()
	Construct a SysTick clock object instance.

virtual	~clock_systick () override
	Destruct the SysTick clock object instance.

Public Member Functions
virtual timestamp_t	now (void)
	Tell the current time, possibly adjusted for epoch.

timestamp_t	steady_now (void)
	Tell the current time since startup.

result_t	sleep_for (duration_t duration)
	Sleep for a relative duration.

virtual result_t	sleep_until (timestamp_t timestamp)
	Sleep until an absolute timestamp.

result_t	wait_for (duration_t timeout)
	Timed wait for an event.

timestamp_t	update_for_slept_time (duration_t duration)
	Increase the internal count after a deep sleep.

Public Member Functions
const char *	name (void) const
	Get object name.

Static Public Attributes
Types & Constants
static constexpr uint32_t	frequency_hz = OS_INTEGER_SYSTICK_FREQUENCY_HZ
	SysTick frequency in Hz.

Public Member Functions
virtual void	start (void) override

template<typename Rep_T >
static constexpr clock::duration_t	ticks_cast (Rep_T microsec)
	Convert microseconds to ticks.

Detailed Description

SysTick derived clock.

This clock counts SysTick interrupts since startup.

The SysTick clock should be a steady clock, i.e. the total count of ticks should be monotone ascending (in other words no adjustments to the past should be performed).

For Cortex-M implementations using the standard SysTick, this clock is able to provide accuracy at CPU cycle level, by sampling the SysTick internal counter. For a CPU clock of 100 MHz, this gives a 10 ns resolution, quite high for accurate timing.

Example

void
func(void)
{
   // Do something
 
   // Get the current ticks counter.
   clock::timestamp_t ticks = sysclock.now();
 
   // Put the current thread to sleep for a given number of ticks.
   sysclock.sleep_for(7);
 
   // Put the current thread to sleep for a given number of microseconds.
   // For a 1000 Hz clock, the actual value is 4 ticks.
   sysclock.sleep_for(clock_systick::ticks_cast((uint64_t)(3500)));
 
   // Do something else.
}

Definition at line 468 of file os-clocks.h.

Constructor & Destructor Documentation

◆ clock_systick()

os::rtos::clock_systick::clock_systick ( )

Construct a SysTick clock object instance.

Warning: Cannot be invoked from Interrupt Service Routines.

Definition at line 550 of file os-clocks.cpp.

◆ ~clock_systick()

os::rtos::clock_systick::~clock_systick ( )

overridevirtual

Destruct the SysTick clock object instance.

Warning: Cannot be invoked from Interrupt Service Routines.

Definition at line 560 of file os-clocks.cpp.

Member Function Documentation

◆ name()

const char * os::rtos::internal::object_named::name ( void ) const

inlineinherited

Get object name.

Parameters: None.

Returns: A null terminated string.

All objects return a non-null string; anonymous objects return "-".

Note: Can be invoked from Interrupt Service Routines.

Definition at line 774 of file os-decls.h.

◆ now()

clock::timestamp_t os::rtos::clock::now ( void )

virtualinherited

Tell the current time, possibly adjusted for epoch.

Parameters: None.

Returns: The clock current timestamp (time units from startup plus the epoch offset).

Note: Can be invoked from Interrupt Service Routines.

Reimplemented in os::rtos::adjustable_clock, and os::rtos::clock_highres.

Definition at line 173 of file os-clocks.cpp.

◆ sleep_for()

result_t os::rtos::clock::sleep_for ( duration_t duration )

inherited

Sleep for a relative duration.

Parameters

[in] duration The number of clock units (ticks or seconds) to sleep.

Return values

ETIMEDOUT	The sleep lasted the entire duration.
EPERM	Cannot be invoked from an Interrupt Service Routines.
EINTR	The sleep was interrupted.

Warning: Cannot be invoked from Interrupt Service Routines.

Definition at line 201 of file os-clocks.cpp.

◆ sleep_until()

result_t os::rtos::clock::sleep_until ( timestamp_t timestamp )

virtualinherited

Sleep until an absolute timestamp.

Parameters

[in] timestamp The absolute moment in time, in clock units.

Return values

ETIMEDOUT	The sleep lasted the entire duration.
EPERM	Cannot be invoked from an Interrupt Service Routines.
EINTR	The sleep was interrupted.

Warning: Cannot be invoked from Interrupt Service Routines.

Reimplemented in os::rtos::adjustable_clock.

Definition at line 243 of file os-clocks.cpp.

◆ start()

void os::rtos::clock_systick::start ( void )

overridevirtual

Warning: Cannot be invoked from Interrupt Service Routines.

Implements os::rtos::clock.

Definition at line 569 of file os-clocks.cpp.

◆ steady_now()

clock::timestamp_t os::rtos::clock::steady_now ( void )

inherited

Tell the current time since startup.

Parameters: None.

Returns: The clock current steady timestamp (time units from startup).

Note: Can be invoked from Interrupt Service Routines.

Definition at line 187 of file os-clocks.cpp.

◆ ticks_cast()

template<typename Rep_T >

static constexpr clock::duration_t os::rtos::clock_systick::ticks_cast ( Rep_T microsec )

staticconstexpr

Convert microseconds to ticks.

Template Parameters

Rep_T Type of input, auto deduced (usually uint32_t or uin64_t)

Parameters

[in] microsec The number of microseconds.

Returns: The number of ticks.

◆ update_for_slept_time()

clock::timestamp_t os::rtos::clock::update_for_slept_time ( duration_t duration )

inherited

Increase the internal count after a deep sleep.

Parameters

duration Number of ticks lost during sleep.

Returns: The clock current steady timestamp (time units from startup).

During deep sleep the interrupts used to count clock ticks are usually disabled and an external RTC is configured to wake-up the device, so a number of clock ticks are lost.

To keep the clocks accurate, it is recommended to sample the external RTC before entering deep sleep and again when the device is back to life, compute the time slept as difference, and use this function to update the internal clock counter.

Definition at line 324 of file os-clocks.cpp.

◆ wait_for()

result_t os::rtos::clock::wait_for ( duration_t timeout )

inherited

Timed wait for an event.

Parameters

[in] timeout The timeout in clock units.

Return values

result::ok	An event occurred before the timeout.
ETIMEDOUT	The wait lasted the entire duration.
EPERM	Cannot be invoked from an Interrupt Service Routines.
EINTR	The sleep was interrupted.

Warning: Cannot be invoked from Interrupt Service Routines.

Definition at line 282 of file os-clocks.cpp.

Member Data Documentation

◆ frequency_hz

constexpr uint32_t os::rtos::clock_systick::frequency_hz = OS_INTEGER_SYSTICK_FREQUENCY_HZ

staticconstexpr

SysTick frequency in Hz.

Definition at line 480 of file os-clocks.h.

The documentation for this class was generated from the following files:

Public Types

Public Member Functions

Static Public Attributes

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ clock_systick()

◆ ~clock_systick()

Member Function Documentation

◆ name()

◆ now()

◆ sleep_for()

◆ sleep_until()

◆ start()

◆ steady_now()

◆ ticks_cast()

◆ update_for_slept_time()

◆ wait_for()

Member Data Documentation

◆ frequency_hz