docs/modules/tmr.md
| 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.
!!! attention
NodeMCU formerly provided 7 static timers, numbered 0-6, which could be
used instead of OO API timers initiated with [`tmr.create()`](#tmrcreate).
After a long period of deprecation, these were removed in 2019 Q1.
Creates a dynamic timer object; see below for its method table.
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:
none
timer object
local mytimer = tmr.create()
mytimer:register(5000, tmr.ALARM_SINGLE, function (t) print("expired"); t:unregister() end)
mytimer:start()
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.
tmr.delay(us)
us microseconds to busyloop for
nil
tmr.delay(100)
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.
tmr.now()
none
the current value of the system counter
print(tmr.now())
print(tmr.now())
Provides a simple software watchdog, which needs to be re-armed or disabled before it expires, or the system will be restarted.
tmr.softwd(timeout_s)
timeout_s watchdog timeout, in seconds. To disable the watchdog, use -1 (or any other negative value).
nil
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)
Returns the system uptime, in seconds. Limited to 31 bits, after that it wraps around back to zero.
tmr.time()
none
the system uptime, in seconds, possibly wrapped around
print("Uptime (probably):", tmr.time())
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.
tmr.wdclr()
none
nil
Get value of CPU CCOUNT register which contains CPU ticks. The register is 32-bit and rolls over.
Converting the register's CPU ticks to us is done by dividing it to 80 or 160 (CPU80/CPU160) i.e. tmr.ccount() / node.getcpufreq().
Register arithmetic works without need to account for roll over, unlike tmr.now(). Because of same reason when CCOUNT is having its 32nd bit set, it appears in Lua as negative number.
tmr.ccount()
The current value of CCOUNT register.
function timeIt(fnc, cnt)
local function loopIt(f2)
local t0 = tmr.ccount()
for i=1,cnt do
f2()
end
local t1 = tmr.ccount()
return math.ceil((t1-t0)/cnt)
end
assert(type(fnc) == "function", "function to test missing")
cnt = cnt or 1000
local emptyTime = loopIt(function()end)
local deltaCPUTicks = math.abs(loopIt(fnc) - emptyTime)
local deltaUS = math.ceil(deltaCPUTicks/node.getcpufreq())
return deltaCPUTicks, deltaUS
end
print( timeIt(function() tmr.ccount() end) )
This is a convenience function combining tobj:register() and tobj:start() into a single call. This is the reason why this method has the same parameters as tobj:register().
If tobj:alarm() is invoked on an already running timer the timer is stopped, new parameters are set and timer is (re)started (similar to call tobj:start(true)).
To free up the resources with this timer when done using it, call tobj:unregister() on it. For one-shot timers this is not necessary, unless they were stopped before they expired.
tobj:alarm(interval_ms, mode, func())
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 unregister())tmr.ALARM_SEMI manually repeating alarm (call start() to restart)tmr.ALARM_AUTO automatically repeating alarmfunc(timer) callback function which is invoked with the timer object as an argumenttrue if the timer was started, false on error
if not tmr.create():alarm(5000, tmr.ALARM_SINGLE, function()
print("hey there")
end)
then
print("whoopsie")
end
Changes a registered timer's expiry interval.
tobj:interval(interval_ms)
interval_ms new timer interval in milliseconds. Maximum value is 6870947 (1:54:30.947).nil
mytimer = tmr.create()
mytimer:register(10000, tmr.ALARM_AUTO, function() print("hey there") end)
mytimer:interval(3000) -- actually, 3 seconds is better!
mytimer:start()
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 tobj:unregister() on it. For one-shot timers this is not necessary, unless they were stopped before they expired.
tobj:register(interval_ms, mode, func())
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 tobj:unregister())tmr.ALARM_SEMI manually repeating alarm (call tobj:start() to restart)tmr.ALARM_AUTO automatically repeating alarmfunc(timer) callback function which is invoked with the timer object as an argumentNote that registering does not start the alarm.
nil
mytimer = tmr.create()
mytimer:register(5000, tmr.ALARM_SINGLE, function() print("hey there") end)
mytimer:start()
Starts or restarts a previously configured timer. If the timer is running the timer is restarted only when restart parameter is true. Otherwise false is returned signaling error.
tobj:start([restart])
restart optional boolean parameter forcing to restart already running timertrue if the timer was (re)started, false on error
mytimer = tmr.create()
mytimer:register(5000, tmr.ALARM_SINGLE, function() print("hey there") end)
if not mytimer:start() then print("uh oh") end
Checks the state of a timer.
tobj:state()
None
(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.
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
Stops a running timer, but does not unregister it. A stopped timer can be restarted with tobj:start().
tobj:stop()
None
true if the timer was stopped, false on error
mytimer = tmr.create()
if not mytimer:stop() then print("timer not stopped, not registered?") end
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.
tobj:unregister()
None
nil