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diff --git a/docs/library/machine.TimerWiPy.rst b/docs/library/machine.TimerWiPy.rst new file mode 100644 index 000000000..abbcc28ff --- /dev/null +++ b/docs/library/machine.TimerWiPy.rst @@ -0,0 +1,159 @@ +.. currentmodule:: machine +.. _machine.TimerWiPy: + +class TimerWiPy -- control hardware timers +========================================== + +.. note:: + + 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 :ref:`machine.Timer <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 :ref:`important constraints <machine_callbacks>` on +Timer callbacks. + +.. note:: + + Memory can't be allocated inside irq handlers (an interrupt) and so + exceptions raised within a handler don't give much information. See + :func:`micropython.alloc_emergency_exception_buf` for how to get around this + limitation. + +Constructors +------------ + +.. class:: TimerWiPy(id, ...) + + Construct a new timer object of the given id. Id of -1 constructs a + virtual timer (if supported by a board). + +Methods +------- + +.. method:: TimerWiPy.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 + + Keyword arguments: + + - ``mode`` can 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. + + - ``width`` must 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 ``ONE_SHOT`` AND ``PERIODIC`` modes. + +.. method:: TimerWiPy.deinit() + + Deinitialises the timer. Stops the timer, and disables the timer peripheral. + +.. method:: TimerWiPy.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 ``None`` if 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. + + - ``channel`` if the width of the timer is 16-bit, then must be either ``TIMER.A``, ``TIMER.B``. + If the width is 32-bit then it **must be** ``TIMER.A | TIMER.B``. + + Keyword only arguments: + + - ``freq`` sets the frequency in Hz. + - ``period`` sets the period in microseconds. + + .. note:: + + Either ``freq`` or ``period`` must be given, never both. + + - ``polarity`` this is applicable for ``PWM``, and defines the polarity of the duty cycle + - ``duty_cycle`` only 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. + + .. note:: + + 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 ``Pin`` class. The pins which + support PWM functionality are the following: + + - ``GP24`` on Timer 0 channel A. + - ``GP25`` on Timer 1 channel A. + - ``GP9`` on Timer 2 channel B. + - ``GP10`` on Timer 3 channel A. + - ``GP11`` on 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. + +Methods +------- + +.. method:: timerchannel.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.PERIODIC`` the callback is executed periodically + with the configured frequency or period. + - If mode is ``TimerWiPy.ONE_SHOT`` the callback is executed once when + the configured timer expires. + - If mode is ``TimerWiPy.PWM`` the callback is executed when reaching the duty + cycle value. + + The accepted params are: + + - ``priority`` level of the interrupt. Can take values in the range 1-7. + Higher values represent higher priorities. + - ``handler`` is an optional function to be called when the interrupt is triggered. + - ``trigger`` must be ``TimerWiPy.TIMEOUT`` when the operating mode is either ``TimerWiPy.PERIODIC`` or + ``TimerWiPy.ONE_SHOT``. In the case that mode is ``TimerWiPy.PWM`` then trigger must be equal to + ``TimerWiPy.MATCH``. + + Returns a callback object. + +.. method:: timerchannel.freq([value]) + + Get or set the timer channel frequency (in Hz). + +.. method:: timerchannel.period([value]) + + Get or set the timer channel period (in microseconds). + +.. method:: timerchannel.duty_cycle([value]) + + 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. + +Constants +--------- + +.. data:: TimerWiPy.ONE_SHOT +.. data:: TimerWiPy.PERIODIC + + Timer operating mode. |