Timer Module

Since Origin / Contributor Maintainer Source
2014-12-12 Zeroday dnc40085 tmr.c

The tmr module allows access to simple timers. It is aimed at setting up regularly occurring tasks and timing out operations.

What the tmr module is not however, is a time keeping module. While all timeouts are expressed in milliseconds, the accuracy is limited and compounding errors would lead to rather inaccurate time keeping. A module for "wall clock" time is not yet available.

Note

The resolution of the timers is determined by FreeRTOS' tick rate. The default rate of 100 kHz (resulting in 10 ms resolution) can be changed with make menuconfig at item Component config ---> FreeRTOS ---> Tick rate (Hz).

tmr.create()

Creates a dynamic timer object.

Parameters

none

Returns

timer object

Example

local mytimer = tmr.create()

-- oo calling
mytimer:register(5000, tmr.ALARM_SINGLE, function (t) print("expired") end)
mytimer:start()
mytimer = nil

tmr Object

tmr.obj:alarm()

This is a convenience function combining tmr.obj:register() and tmr.obj:start() into a single call.

To free up the resources with this timer when done using it, call tmr.obj:unregister() on it. For one-shot timers this is not necessary, unless they were stopped before they expired.

Syntax

mytmr:alarm(interval_ms, mode, func())

Parameters

  • interval_ms timer interval in milliseconds. Maximum value is 6870947 (1:54:30.947).
  • mode timer mode:
    • tmr.ALARM_SINGLE a one-shot alarm (and no need to call tmr.unregister())
    • tmr.ALARM_SEMI manually repeating alarm (call tmr.start() to restart)
    • tmr.ALARM_AUTO automatically repeating alarm
  • func(timer) callback function which is invoked with the timer object as an argument

Returns

true if the timer was started, false on error

Example

if not tmr.create():alarm(5000, tmr.ALARM_SINGLE, function()
  print("hey there")
end)
then
  print("whoopsie")
end

See also

tmr.obj:interval()

Changes a registered timer's expiry interval.

Syntax

mytmr:interval(interval_ms)

Parameters

  • interval_ms new timer interval in milliseconds. Maximum value is 6870947 (1:54:30.947).

Returns

nil

Example

mytimer = tmr.create()
mytimer:register(10000, tmr.ALARM_AUTO, function() print("hey there") end)
mytimer:interval(3000) -- actually, 3 seconds is better!
mytimer:start()

tmr.obj:register()

Configures a timer and registers the callback function to call on expiry.

To free up the resources with this timer when done using it, call tmr.obj:unregister() on it. For one-shot timers this is not necessary, unless they were stopped before they expired.

Syntax

mytmr:register(interval_ms, mode, func())

Parameters

  • interval_ms timer interval in milliseconds. Maximum value is 6870947 (1:54:30.947).
  • mode timer mode:
    • tmr.ALARM_SINGLE a one-shot alarm (and no need to call tmr.unregister())
    • tmr.ALARM_SEMI manually repeating alarm (call tmr.start() to restart)
    • tmr.ALARM_AUTO automatically repeating alarm
  • func(timer) callback function which is invoked with the timer object as an argument

Note that registering does not start the alarm.

Returns

nil

Example

mytimer = tmr.create()
mytimer:register(5000, tmr.ALARM_SINGLE, function() print("hey there") end)
mytimer:start()

See also

tmr.obj:start()

Starts or restarts a previously configured timer.

Syntax

mytmr:start()

Parameters

none

Returns

true if the timer was started, false on error

Example

mytimer = tmr.create()
mytimer:register(5000, tmr.ALARM_SINGLE, function() print("hey there") end)
if not mytimer:start() then print("uh oh") end

See also

tmr.obj:state()

Checks the state of a timer.

Syntax

mytmr:state()

Parameters

none

Returns

(bool, int) or nil

If the specified timer is registered, returns whether it is currently started and its mode. If the timer is not registered, nil is returned.

Example

mytimer = tmr.create()
print(mytimer:state()) -- nil
mytimer:register(5000, tmr.ALARM_SINGLE, function() print("hey there") end)
running, mode = mytimer:state()
print("running: " .. tostring(running) .. ", mode: " .. mode) -- running: false, mode: 0

tmr.obj:stop()

Stops a running timer, but does not unregister it. A stopped timer can be restarted with tmr.obj:start().

Syntax

mytmr:stop()

Parameters

none

Returns

true if the timer was stopped, false on error

Example

mytimer = tmr.create()
if not mytimer:stop() then print("timer not stopped, not registered?") end

See also

tmr.obj:unregister()

Stops the timer (if running) and unregisters the associated callback.

This isn't necessary for one-shot timers (tmr.ALARM_SINGLE), as those automatically unregister themselves when fired.

Syntax

mytmr:unregister()

Parameters

none

Returns

nil

See also

tmr.obj:register()