from machine import Pin, PWM 
from time import sleep_ms
#led = PWM(Pin(2)) 
led = Pin(2, Pin.OUT) 
pwm = PWM(led)
i = 0

while True:
    for i in range(1024): 
        pwm.duty(i) 
        sleep_ms(15)
    for i in range(1023, -1, -1): 
        pwm.duty(i)
        sleep_ms(15)
# function for() to create decremental value by 1 start from 1023 --> 0 
# from OFF LED to linear increasing brightness, for active-low circuit.
# for loop in range concept "for _ in range (start,end,step)"