5. 硬件定时器¶
定时器可用于各种各样的任务，定期调用函数、计数事件和生成 PWM 信号是最常见的用例。每个定时器由两个 16 位通道组成，这些通道可以连接在一起形成一个 32 位定时器。每个定时器都需要配置操作模式，但随后可以在每个通道上独立配置周期（或频率）。通过使用回调方法，定时器事件可以调用 Python 函数。
以固定频率切换 LED 的示例用法：
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
使用命名函数进行回调的示例：
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
进一步的例子：
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