from machine import Pin,PWM
import time


led = Pin(26, Pin.OUT, value=0)
pwm=PWM(led,freq=1000,duty=0)
#Pin(26)
#pwm.duty(1023)
#pwm.duty(512)
pwm.duty(0)
for i in range(1024):
    pwm.duty(i)
    time.sleep_ms(5)
for i in range(1023, 0, -1):  # 从1023递减到0
    pwm.duty(i)
    time.sleep_ms(5)