8.4 KiB
Timer Module
| Since | Origin / Contributor | Maintainer | Source |
|---|---|---|---|
| 2014-12-12 | Zeroday | dnc40085 | tmr.c |
The tmr module allows access to simple timers, the system counter and uptime.
It is aimed at setting up regularly occurring tasks, timing out operations, and provide low-resolution deltas.
What the tmr module is not however, is a time keeping module. While most timeouts are expressed in milliseconds or even microseconds, the accuracy is limited and compounding errors would lead to rather inaccurate time keeping. Consider using the rtctime module for "wall clock" time.
NodeMCU provides 7 static timers, numbered 0-6, and dynamic timer creation function tmr.create().
!!! attention
Static timers are deprecated and will be removed later.
tmr.alarm()
This is a convenience function combining tmr.register() and tmr.start() into a single call.
To free up the resources with this timer when done using it, call tmr.unregister() on it. For one-shot timers this is not necessary, unless they were stopped before they expired.
Parameters
id/reftimer id (0-6) or objectinterval_mstimer interval in milliseconds. Maximum value is 6870947 (1:54:30.947).modetimer mode:tmr.ALARM_SINGLEa one-shot alarm (and no need to calltmr.unregister())tmr.ALARM_SEMImanually repeating alarm (calltmr.start()to restart)tmr.ALARM_AUTOautomatically repeating alarm
Returns
true if the timer was started, false on error
Example
if not tmr.alarm(0, 5000, tmr.ALARM_SINGLE, function() print("hey there") end) then print("whoopsie") end
See also
tmr.create()
Creates a dynamic timer object.
Dynamic timer can be used instead of numeric ID in control functions. Also can be controlled in object-oriented way.
Functions supported in timer object:
Parameters
none
Returns
timer object
Example
local mytimer = tmr.create()
-- oo calling
mytimer:register(5000, tmr.ALARM_SINGLE, function (t) print("expired"); t:unregister() end)
mytimer:start()
-- with self parameter
tmr.register(mytimer, 5000, tmr.ALARM_SINGLE, function (t) print("expired"); tmr.unregister(t) end)
tmr.start(mytimer)
tmr.delay()
Busyloops the processor for a specified number of microseconds.
This is in general a bad idea, because nothing else gets to run, and the networking stack (and other things) can fall over as a result. The only time tmr.delay() may be appropriate to use is if dealing with a peripheral device which needs a (very) brief delay between commands, or similar. Use with caution!
Also note that the actual amount of time delayed for may be noticeably greater, both as a result of timing inaccuracies as well as interrupts which may run during this time.
Syntax
tmr.delay(us)
Parameters
us microseconds to busyloop for
Returns
nil
Example
tmr.delay(100)
tmr.interval()
Changes a registered timer's expiry interval.
Syntax
tmr.interval(id/ref, interval_ms)
Parameters
id/reftimer id (0-6) or objectinterval_msnew timer interval in milliseconds. Maximum value is 6870947 (1:54:30.947).
Returns
nil
Example
tmr.register(0, 5000, tmr.ALARM_SINGLE, function() print("hey there") end)
tmr.interval(0, 3000) -- actually, 3 seconds is better!
tmr.now()
Returns the system counter, which counts in microseconds. Limited to 31 bits, after that it wraps around back to zero. That is essential if you use this function to debounce or throttle GPIO input.
Syntax
tmr.now()
Parameters
none
Returns
the current value of the system counter
Example
print(tmr.now())
print(tmr.now())
tmr.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.unregister() on it. For one-shot timers this is not necessary, unless they were stopped before they expired.
Syntax
tmr.register(id/ref, interval_ms, mode, func)
Parameters
id/reftimer id (0-6) or objectinterval_mstimer interval in milliseconds. Maximum value is 6870947 (1:54:30.947).modetimer mode:tmr.ALARM_SINGLEa one-shot alarm (and no need to calltmr.unregister())tmr.ALARM_SEMImanually repeating alarm (calltmr.start()to restart)tmr.ALARM_AUTOautomatically repeating alarm
Note that registering does not start the alarm.
Returns
nil
Example
tmr.register(0, 5000, tmr.ALARM_SINGLE, function() print("hey there") end)
tmr.start(0)
See also
tmr.softwd()
Provides a simple software watchdog, which needs to be re-armed or disabled before it expires, or the system will be restarted.
Syntax
tmr.softwd(timeout_s)
Parameters
timeout_s watchdog timeout, in seconds. To disable the watchdog, use -1 (or any other negative value).
Returns
nil
Example
function on_success_callback()
tmr.softwd(-1)
print("Complex task done, soft watchdog disabled!")
end
tmr.softwd(5)
-- go off and attempt to do whatever might need a restart to recover from
complex_stuff_which_might_never_call_the_callback(on_success_callback)
tmr.start()
Starts or restarts a previously configured timer.
Syntax
tmr.start(id/ref)
Parameters
id/ref timer id (0-6) or object
Returns
true if the timer was started, false on error
Example
tmr.register(0, 5000, tmr.ALARM_SINGLE, function() print("hey there") end)
if not tmr.start(0) then print("uh oh") end
See also
tmr.state()
Checks the state of a timer.
Syntax
tmr.state(id/ref)
Parameters
id/ref timer id (0-6) or object
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
running, mode = tmr.state(0)
tmr.stop()
Stops a running timer, but does not unregister it. A stopped timer can be restarted with tmr.start().
Syntax
tmr.stop(id/ref)
Parameters
id/ref timer id (0-6) or object
Returns
true if the timer was stopped, false on error
Example
if not tmr.stop(2) then print("timer 2 not stopped, not registered?") end
See also
tmr.time()
Returns the system uptime, in seconds. Limited to 31 bits, after that it wraps around back to zero.
Syntax
tmr.time()
Parameters
none
Returns
the system uptime, in seconds, possibly wrapped around
Example
print("Uptime (probably):", tmr.time())
tmr.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
tmr.unregister(id/ref)
Parameters
id/ref timer id (0-6) or object
Returns
nil
Example
tmr.unregister(0)
See also
tmr.wdclr()
Feed the system watchdog.
In general, if you ever need to use this function, you are doing it wrong.
The event-driven model of NodeMCU means that there is no need to be sitting in hard loops waiting for things to occur. Rather, simply use the callbacks to get notified when somethings happens. With this approach, there should never be a need to manually feed the system watchdog.
Syntax
tmr.wdclr()
Parameters
none
Returns
nil