# ESP32 MicroPython — 4-bit LED Chaser (Knight Rider) 
from machine import Pin
import time

# --- LED pin order (left -> right) ---
LED_PINS = [19, 18, 5, 17]
leds = [Pin(p, Pin.OUT, value=0) for p in LED_PINS]

# --- 4-bit software register (leftmost bit is index 0) ---
register = [1, 0, 0, 0]   # start with the left LED ON
direction = 1             # +1 = move right, -1 = move left

def shift_right(reg, new_bit):
    """Slide all bits one position to the RIGHT; insert new_bit at left (index 0)."""
    for i in range(len(reg) - 1, 0, -1):
        reg[i] = reg[i - 1]
    reg[0] = new_bit
    return reg

def shift_left(reg, new_bit):
    """Slide all bits one position to the LEFT; insert new_bit at the right end."""
    for i in range(0, len(reg) - 1):
        reg[i] = reg[i + 1]
    reg[len(reg) - 1] = new_bit
    return reg

def write_register_to_leds():
    """Parallel-out: show the whole register on the LEDs at once."""
    for i, led in enumerate(leds):
        led.value(register[i])

# --- Main loop = software clock ---
while True:
    # Show current register state on LEDs
    write_register_to_leds()

    # Small delay controls animation speed
    time.sleep_ms(150)

    # Decide which way to shift
    if direction == 1:
        shift_right(register, 0)
        if register == [0, 0, 0, 1]:
            direction = -1
    else:
        shift_left(register, 0)
        if register == [1, 0, 0, 0]:
            direction = 1