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

# Constants
B_REF = 0.5               # Target brightness
MAX_ADC = 4095            # 12-bit ADC max value
SERVO_MIN = 0             # 0° PWM duty
SERVO_MAX = 180           # 180° PWM duty
Kp, Ki, Kd = 30, 5, 10    # PID gains
DT = 1.0                  # Time step

# Hardware setup
ldr = ADC(Pin(4))              # LDR sensor
ldr.atten(ADC.ATTN_11DB)       # Full voltage input
servo = PWM(Pin(41))           # Servo motor
servo.freq(50)                 # Servo PWM frequency

# Control variables
integral = 0
last_error = 0

# Helper functions
def brightness():
    return 1.0 - (ldr.read() / MAX_ADC)  # Inverted brightness

def clamp(u):
    return max(SERVO_MIN, min(SERVO_MAX, int(u)))  # Keep angle in 0–180

# Logging header
print("t\tb(t)\te(t)\tu(t)")

# Simulation loop: 0 to 50 seconds
for t in range(51):
    b = brightness()
    error = b - B_REF
    integral += error * DT
    derivative = (error - last_error) / DT

    # PID control
    u = clamp(Kp * error + Ki * integral + Kd * derivative + 90)
    servo.duty(u)  # direct duty set, same as your original logic

    print(f"{t}\t{b:.3f}\t{error:.3f}\t{u}")

    last_error = error
    sleep(1)