from machine import Pin
import time

# Define GPIO pins for the LEDs (D0 - D3)
led_pins = [15, 14, 13, 12]

# Initialize LED pins as output
leds = [Pin(pin_num, Pin.OUT) for pin_num in led_pins]

def display_binary(value):
    # Display the 4-bit binary representation on the LEDs
    for i in range(4):
        bit = (value >> i) & 1
        leds[i].value(bit)

# Main loop
counter = 0
while True:
    display_binary(counter)
    print(f"Counter: {counter} (Binary: {counter:04b})")  # <-- Added print here
    time.sleep(1)  # Wait for 1 second
    counter = (counter + 1) % 16  # Loop back after 15