class Timer – control hardware timers¶
Hardware timers deal with timing of periods and events. Timers are perhaps the most flexible and heterogeneous kind of hardware in MCUs and SoCs, differently greatly from a model to a model. MicroPython’s Timer class defines a baseline operation of executing a callback with a given period (or once after some delay), and allow specific boards to define more non-standard behaviour (which thus won’t be portable to other boards).
See discussion of important constraints on Timer callbacks.
Memory can’t be allocated inside irq handlers (an interrupt) and so
exceptions raised within a handler don’t give much information. See
micropython.alloc_emergency_exception_buf() for how to get around this
- class machine.Timer(id, /, ...)¶
Construct a new timer object of the given
idof -1 constructs a virtual timer (if supported by a board).
idshall not be passed as a keyword argument.
initfor parameters of initialisation.
- Timer.init(*, mode=Timer.PERIODIC, freq=-1, period=-1, callback=None)¶
Initialise the timer. Example:
def mycallback(t): pass # periodic at 1kHz tim.init(mode=Timer.PERIODIC, freq=1000, callback=mycallback) # periodic with 100ms period tim.init(period=100, callback=mycallback) # one shot firing after 1000ms tim.init(mode=Timer.ONE_SHOT, period=1000, callback=mycallback)
modecan be one of:
Timer.ONE_SHOT- The timer runs once until the configured period of the channel expires.
Timer.PERIODIC- The timer runs periodically at the configured frequency of the channel.
freq- The timer frequency, in units of Hz. The upper bound of the frequency is dependent on the port. When both the
periodarguments are given,
freqhas a higher priority and
period- The timer period, in milliseconds.
callback- The callable to call upon expiration of the timer period. The callback must take one argument, which is passed the Timer object. The
callbackargument shall be specified. Otherwise an exception will occurr upon timer expiration:
TypeError: 'NoneType' object isn't callable
Deinitialises the timer. Stops the timer, and disables the timer peripheral.