71 lines
3.1 KiB
ReStructuredText
71 lines
3.1 KiB
ReStructuredText
Hardware timers
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===============
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Timers can be used for a great variety of tasks, calling a function periodically,
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counting events, and generating a PWM signal are among the most common use cases.
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Each timer consists of two 16-bit channels and this channels can be tied together to
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form one 32-bit timer. The operating mode needs to be configured per timer, but then
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the period (or the frequency) can be independently configured on each channel.
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By using the callback method, the timer event can call a Python function.
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Example usage to toggle an LED at a fixed frequency::
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from machine import Timer
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from machine import Pin
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led = Pin('GP16', mode=Pin.OUT) # enable GP16 as output to drive the LED
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tim = Timer(3) # create a timer object using timer 3
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tim.init(mode=Timer.PERIODIC) # initialize it in periodic mode
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tim_ch = tim.channel(Timer.A, freq=5) # configure channel A at a frequency of 5Hz
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tim_ch.irq(handler=lambda t:led.toggle(), trigger=Timer.TIMEOUT) # toggle a LED on every cycle of the timer
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Example using named function for the callback::
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from machine import Timer
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from machine import Pin
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tim = Timer(1, mode=Timer.PERIODIC, width=32)
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tim_a = tim.channel(Timer.A | Timer.B, freq=1) # 1 Hz frequency requires a 32 bit timer
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led = Pin('GP16', mode=Pin.OUT) # enable GP16 as output to drive the LED
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def tick(timer): # we will receive the timer object when being called
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global led
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led.toggle() # toggle the LED
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tim_a.irq(handler=tick, trigger=Timer.TIMEOUT) # create the interrupt
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Further examples::
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from machine import Timer
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tim1 = Timer(1, mode=Timer.ONE_SHOT) # initialize it in one shot mode
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tim2 = Timer(2, mode=Timer.PWM) # initialize it in PWM mode
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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
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tim2_ch = tim2.channel(Timer.B, freq=10000, duty_cycle=5000) # start the PWM on channel B with a 50% duty cycle
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tim2_ch.freq(20) # set the frequency (can also get)
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tim2_ch.duty_cycle(3010) # set the duty cycle to 30.1% (can also get)
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tim2_ch.duty_cycle(3020, Timer.NEGATIVE) # set the duty cycle to 30.2% and change the polarity to negative
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tim2_ch.period(2000000) # change the period to 2 seconds
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Additional constants for Timer class
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------------------------------------
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.. data:: Timer.PWM
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PWM timer operating mode.
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.. data:: Timer.A
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.. data:: Timer.B
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Selects the timer channel. Must be ORed (``Timer.A`` | ``Timer.B``) when
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using a 32-bit timer.
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.. data:: Timer.POSITIVE
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.. data:: Timer.NEGATIVE
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Timer channel polarity selection (only relevant in PWM mode).
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.. data:: Timer.TIMEOUT
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.. data:: Timer.MATCH
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Timer channel IRQ triggers.
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