class TimerWiPy – control hardware timers¶
This class is a non-standard Timer implementation for the WiPy.
It is available simply as
machine.Timer on the WiPy but is named in the
documentation below as
machine.TimerWiPy to distinguish it from the
more general machine.Timer class.
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 behavior (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
Construct a new timer object of the given id. Id of -1 constructs a virtual timer (if supported by a board).
init(mode, *, width=16)¶
Initialise the timer. Example:
tim.init(Timer.PERIODIC) # periodic 16-bit timer tim.init(Timer.ONE_SHOT, width=32) # one shot 32-bit timer
modecan be one of:
TimerWiPy.ONE_SHOT- The timer runs once until the configured period of the channel expires.
TimerWiPy.PERIODIC- The timer runs periodically at the configured frequency of the channel.
TimerWiPy.PWM- Output a PWM signal on a pin.
widthmust be either 16 or 32 (bits). For really low frequencies < 5Hz (or large periods), 32-bit timers should be used. 32-bit mode is only available for
Deinitialises the timer. Stops the timer, and disables the timer peripheral.
channel(channel, **, freq, period, polarity=TimerWiPy.POSITIVE, duty_cycle=0)¶
If only a channel identifier passed, then a previously initialized channel object is returned (or
Noneif there is no previous channel).
Otherwise, a TimerChannel object is initialized and returned.
The operating mode is is the one configured to the Timer object that was used to create the channel.
channelif the width of the timer is 16-bit, then must be either
TIMER.B. If the width is 32-bit then it must be
TIMER.A | TIMER.B.
Keyword only arguments:
freqsets the frequency in Hz.
periodsets the period in microseconds.
periodmust be given, never both.
polaritythis is applicable for
PWM, and defines the polarity of the duty cycle
duty_cycleonly applicable to
PWM. It’s a percentage (0.00-100.00). Since the WiPy doesn’t support floating point numbers the duty cycle must be specified in the range 0-10000, where 10000 would represent 100.00, 5050 represents 50.50, and so on.
When the channel is in PWM mode, the corresponding pin is assigned automatically, therefore there’s no need to assign the alternate function of the pin via the
Pinclass. The pins which support PWM functionality are the following:
GP24on Timer 0 channel A.
GP25on Timer 1 channel A.
GP9on Timer 2 channel B.
GP10on Timer 3 channel A.
GP11on Timer 3 channel B.
class TimerChannel — setup a channel for a timer¶
Timer channels are used to generate/capture a signal using a timer.
TimerChannel objects are created using the Timer.channel() method.
irq(*, trigger, priority=1, handler=None)¶
The behavior of this callback is heavily dependent on the operating mode of the timer channel:
- If mode is
TimerWiPy.PERIODICthe callback is executed periodically with the configured frequency or period.
- If mode is
TimerWiPy.ONE_SHOTthe callback is executed once when the configured timer expires.
- If mode is
TimerWiPy.PWMthe callback is executed when reaching the duty cycle value.
The accepted params are:
prioritylevel of the interrupt. Can take values in the range 1-7. Higher values represent higher priorities.
handleris an optional function to be called when the interrupt is triggered.
TimerWiPy.TIMEOUTwhen the operating mode is either
TimerWiPy.ONE_SHOT. In the case that mode is
TimerWiPy.PWMthen trigger must be equal to
Returns a callback object.
- If mode is
Get or set the timer channel frequency (in Hz).
Get or set the timer channel period (in microseconds).
Get or set the duty cycle of the PWM signal. It’s a percentage (0.00-100.00). Since the WiPy doesn’t support floating point numbers the duty cycle must be specified in the range 0-10000, where 10000 would represent 100.00, 5050 represents 50.50, and so on.