You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
70 lines
3.1 KiB
70 lines
3.1 KiB
Hardware timers
|
|
===============
|
|
|
|
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
|
|
|
|
|
|
Additional constants for Timer class
|
|
------------------------------------
|
|
|
|
.. data:: Timer.PWM
|
|
|
|
PWM 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.
|
|
|