A C++ template library for embedded applications
MIT licensed
Designed and
maintained by
John Wellbelove
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Callback Timer Locked


A software timer class that can manage up to 254 timers. Each one may be repeating or single shot.
When a timer triggers it will call the selected function. The function may be a class member or free function.
The timers are driven from a call to tick(uint32_t count). This call would normally be made from a high priority
interrupt routine. The destination function will receive the callback in the same context as the tick call.
The call to tick has a low overhead when a timer is not 'due'. Internally the timers are stored in 'first timeout' order so
only the head of the list needs to be checked.

Each timer may have a period of up to 232-2 ticks (4,294,967,294).
At 1ms per tick this would equate to just over 49 days.

Defines the following classes:-
etl::icallback_timer_locked
etl::callback_timer_locked

The access to the timers is controlled by three external functions, supplied to the timer by the
member function set_locks.

The three delegate parameters are:-
Try Lock  Attempts to set the lock. Returns true if successful, otherwise false.
Lock      Sets the lock.
Unlock    Resets the lock.

Uses definitions from timer.h

Important:
For correct operation of the timer framework, the routine that calls tick must not be pre-emptible by another routine
that calls a timer function. Also, calls to the timer framework may only be made from the caller of tick and one other,
lower priority, thread of execution
____________________________________________________________________________________________________

icallback_timer_locked

The base class for all timer controllers.

Type definitions

callback_type    etl::delegate<void(void)>
The function type used for callbacks.

try_lock_type    etl::delegate<bool(void)>
The function type used for 'try lock'.

lock_type        etl::delegate<void(void)>
The function type used for 'lock'.

unlock_type      etl::delegate<void(void)>
The function type used for 'unlock'.
____________________________________________________________________________________________________

Member functions

etl::timer::id::type register_timer(callback_type callback),
                                    uint32_t      period,                                       
                                    bool          repeating)
Registers a timer calling a free or static function.
callback  A delegate to the callback free funtion that will be callled when the timer expires.
period    The timer period in ticks.
repeating false if single shot, true if repeating.

Returns the allocated timer id or etl::timer::mode::NO_TIMER if one was not available.
____________________________________________________________________________________________________
bool unregister_timer(etl::timer::id::type id)
Unregisters a timer.
If the timer is active then it will be stopped.
Returns true if a timer with the id was successfully unregistered.
___________________________________________________________________________________________________
void enable(bool state)
Enables or disables the timer manager according to the state.
____________________________________________________________________________________________________
bool is_running() const
Returns true if the timer manager is enabled.
____________________________________________________________________________________________________
void clear()
Clears the callback timer back to the initial state. All timers will be stopped and unregistered.
____________________________________________________________________________________________________
bool tick(uint32_t count)
This function updates the internal tick counter (if enabled) and must pass the number of ticks that have occurred since
the last call. If the count encompasses more than one period of a repeating timer then the timer will be triggered
multiple times in one call to tick.
Returns true if the tick counter was updated, otherwise false. This may be used by the calling routine to accumulate
unprocessed tick counts.
____________________________________________________________________________________________________
bool start(etl::timer::id::type id, bool immediate = false)
Starts the timer with the specified id.
If the timer is already running then the timer Is restarted from the current tick count.
If immediate is true then the timer is triggered on the next call to tick(). Note: Single shot timers will only trigger
once.
If the id does not correspond to a registered timer then returns false.
____________________________________________________________________________________________________
bool stop(etl::timer::id::type id)
Stops the timer with the specified id.
Does nothing if the timer is already stopped.
if the id does not correspond to a registered timer then returns false.
____________________________________________________________________________________________________
bool set_period(etl::timer::id::type id, uint32_t period)
Stops the timer with the specified id.
Sets a new timer period.
Returns true if successful.
____________________________________________________________________________________________________
bool set_mode(etl::timer::id::type id, bool repeating)
Stops the timer with the specified id.
Sets a new timer mode.
Returns true if successful.
____________________________________________________________________________________________________
void set_locks(try_lock_type try_lock_, lock_type lock_, lock_type unlock_)
Sets the try-lock, lock and unlock delegates.
____________________________________________________________________________________________________
Constants
MAX_TIMERS
The maximum number of timers that can be handled.
____________________________________________________________________________________________________

callback_timer_locked


Template parameters

MAX_TIMERS The number of timers to be supported. The maximum number is 254.
A value of 255 will result in a compile error.

callback_timer_locked()
Default construct.
The lock callback delegates are not set.
____________________________________________________________________________________________________
callback_timer_locked(try_lock_type try_lock, lock_type lock, unlock_type unlock)
Construct from lock callback delegates.
____________________________________________________________________________________________________

Example


//***************************************************************************
// Class callback via etl::function
//***************************************************************************
class Test
{
public:

  Test()
    : ticks(0)
  {
  }

  void callback()
  {
    ++ticks;
  }

  int ticks;
};
 
using callback_type = etl::icallback_timer_atomic::callback_type;

callback_type member_callback = callback_type::create<Test, test, &Test::callback> member_callback;

//***************************************************************************
// Free function callback via etl::function
//***************************************************************************
int free_ticks1 = 0;

void free_callback1()
{
  ++free_ticks;
}

callback_type free_callback1 = callback_type::create<free_function_callback>();

//***************************************************************************
// Timer controller.
//***************************************************************************
etl::callback_timer<2> timer_controller;

//***************************************************************************
// The main loop.
//***************************************************************************
int main()
{
  etl::timer::id::type id1 = timer_controller.register_timer(member_callback,
                                                             1000,
                                                             etl::timer::mode::SINGLE_SHOT);

  etl::timer::id::type id2 = timer_controller.register_timer(free_function_callback,
                                                             100,
                                                             etl::timer::mode::REPEATING);

  timer_controller.start(id1);
  timer_controller.start(id2);
  timer_controller.start(id3);

  timer_controller.enable(true);

  // Start timer interrupts here.

  while (true)
  {
    // Loop forever.
  }

  return 0;
}

//***************************************************************************
// The interrupt timer callback.
//***************************************************************************
void timer_interrupt()
{
  const uint32_t TICK = 1;
  static uint32_t nticks = TICK;

  if (timer_controller.tick(nticks))
  {
    nticks = TICK;
  }
  else
  {
    nticks += TICK;
  }
}
callback_timer_locked.h