# Simple MicroPython script to fade the onboard LED with perceptual brightness scaling
# using PWM (Pulse Width Modulation) and gamma correction.

from machine import Pin, PWM
from time import sleep
import math

# Set up PWM on the onboard LED (GPIO 25)
pwm_led = PWM(Pin(25))
pwm_led.freq(1000)

# Gamma value for perceptual scaling (approx. 2.2 for human eye)
gamma = 2.2

# Number of steps for the fade (tweak for smoothness/performance)
steps = 100

# Precompute gamma-corrected values for fading
fade_values = [
    int((math.pow(i / steps, gamma)) * 65535)
    for i in range(steps + 1)
]

# Fade loop
while True:
    # Fade in
    for duty in fade_values:
        pwm_led.duty_u16(duty)
        sleep(0.01)

    # Fade out
    for duty in reversed(fade_values):
        pwm_led.duty_u16(duty)
        sleep(0.01)