216 lines
8.4 KiB
ReStructuredText
216 lines
8.4 KiB
ReStructuredText
.. currentmodule:: machine
|
|
|
|
class Timer -- control internal timers
|
|
======================================
|
|
|
|
.. only:: port_wipy
|
|
|
|
Timers can be used for a great variety of tasks, calling a function periodically,
|
|
counting events, and generating a PWM signal are among the most common use cases.
|
|
Each timer consists of two 16-bit channels and this channels can be tied together to
|
|
form one 32-bit timer. The operating mode needs to be configured per timer, but then
|
|
the period (or the frequency) can be independently configured on each channel.
|
|
By using the callback method, the timer event can call a Python function.
|
|
|
|
Example usage to toggle an LED at a fixed frequency::
|
|
|
|
from machine import Timer
|
|
from machine import Pin
|
|
led = Pin('GP16', mode=Pin.OUT) # enable GP16 as output to drive the LED
|
|
tim = Timer(3) # create a timer object using timer 3
|
|
tim.init(mode=Timer.PERIODIC) # initialize it in periodic mode
|
|
tim_ch = tim.channel(Timer.A, freq=5) # configure channel A at a frequency of 5Hz
|
|
tim_ch.irq(handler=lambda t:led.toggle(), trigger=Timer.TIMEOUT) # toggle a LED on every cycle of the timer
|
|
|
|
Example using named function for the callback::
|
|
|
|
from machine import Timer
|
|
from machine import Pin
|
|
tim = Timer(1, mode=Timer.PERIODIC, width=32)
|
|
tim_a = tim.channel(Timer.A | Timer.B, freq=1) # 1 Hz frequency requires a 32 bit timer
|
|
|
|
led = Pin('GP16', mode=Pin.OUT) # enable GP16 as output to drive the LED
|
|
|
|
def tick(timer): # we will receive the timer object when being called
|
|
global led
|
|
led.toggle() # toggle the LED
|
|
|
|
tim_a.irq(handler=tick, trigger=Timer.TIMEOUT) # create the interrupt
|
|
|
|
Further examples::
|
|
|
|
from machine import Timer
|
|
tim1 = Timer(1, mode=Timer.ONE_SHOT) # initialize it in one shot mode
|
|
tim2 = Timer(2, mode=Timer.PWM) # initialize it in PWM mode
|
|
tim1_ch = tim1.channel(Timer.A, freq=10, polarity=Timer.POSITIVE) # start the event counter with a frequency of 10Hz and triggered by positive edges
|
|
tim2_ch = tim2.channel(Timer.B, freq=10000, duty_cycle=5000) # start the PWM on channel B with a 50% duty cycle
|
|
tim2_ch.freq(20) # set the frequency (can also get)
|
|
tim2_ch.duty_cycle(3010) # set the duty cycle to 30.1% (can also get)
|
|
tim2_ch.duty_cycle(3020, Timer.NEGATIVE) # set the duty cycle to 30.2% and change the polarity to negative
|
|
tim2_ch.period(2000000) # change the period to 2 seconds
|
|
|
|
.. 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:: Timer(id, ...)
|
|
|
|
.. only:: port_wipy
|
|
|
|
Construct a new timer object of the given id. ``id`` can take values from 0 to 3.
|
|
|
|
|
|
Methods
|
|
-------
|
|
|
|
.. only:: port_wipy
|
|
|
|
.. method:: Timer.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:
|
|
|
|
- ``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.
|
|
- ``Timer.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:: Timer.deinit()
|
|
|
|
Deinitialises the timer. Disables all channels and associated IRQs.
|
|
Stops the timer, and disables the timer peripheral.
|
|
|
|
.. only:: port_wipy
|
|
|
|
.. method:: Timer.channel(channel, \**, freq, period, polarity=Timer.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
|
|
-------
|
|
|
|
.. only:: port_wipy
|
|
|
|
.. 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 ``Timer.PERIODIC`` the callback is executed periodically
|
|
with the configured frequency or period.
|
|
- If mode is ``Timer.ONE_SHOT`` the callback is executed once when
|
|
the configured timer expires.
|
|
- If mode is ``Timer.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 ``Timer.TIMEOUT`` when the operating mode is either ``Timer.PERIODIC`` or
|
|
``Timer.ONE_SHOT``. In the case that mode is ``Timer.PWM`` then trigger must be equal to
|
|
``Timer.MATCH``.
|
|
|
|
Returns a callback object.
|
|
|
|
.. only:: port_wipy
|
|
|
|
.. 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:: Timer.ONE_SHOT
|
|
.. data:: Timer.PERIODIC
|
|
.. data:: Timer.PWM
|
|
|
|
Selects the timer operating mode.
|
|
|
|
.. data:: Timer.A
|
|
.. data:: Timer.B
|
|
|
|
Selects the timer channel. Must be ORed (``Timer.A`` | ``Timer.B``) when
|
|
using a 32-bit timer.
|
|
|
|
.. data:: Timer.POSITIVE
|
|
.. data:: Timer.NEGATIVE
|
|
|
|
Timer channel polarity selection (only relevant in PWM mode).
|
|
|
|
.. data:: Timer.TIMEOUT
|
|
.. data:: Timer.MATCH
|
|
|
|
Timer channel IRQ triggers.
|