import utime
utime.sleep(0.1) # Wait for USB to become ready

from machine import Pin, I2C, Timer
from pico_i2c_lcd import I2cLcd

sda = Pin(0)
scl = Pin(1)
i2c = I2C(0, sda=sda, scl=scl, freq=40000)
lcd = I2cLcd(i2c, 0x27, 2, 16)

r0_leds = [Pin(i, Pin.OUT) for i in range(2, 6)]
r1_leds = [Pin(i, Pin.OUT) for i in range(6, 10)]
r2_leds = [Pin(i, Pin.OUT) for i in range(10, 14)]
carry_led = Pin(14, Pin.OUT)


def add_4bit_registers(r0, r1):
    result = r0 + r1
    carry = 0
    if result > 15:
        result = result & 0x0F
        carry = 1
    return result, carry


def display_registers(r0, r1, result, carry):
    for i in range(4):
        bit = (r0 >> (3 - i)) & 1
        r0_leds[i].value(bit)
    for i in range(4):
        bit = (r1 >> (3 - i)) & 1
        r1_leds[i].value(bit)
    for i in range(4):
        bit = (result >> (3 - i)) & 1
        r2_leds[i].value(bit)
    carry_led.value(carry)


def display_results(timer):
    lcd.clear()
    for r0 in range(16):
        for r1 in range(16):
            result, carry = add_4bit_registers(r0, r1)
            result_str = f"r0={r0:04b} r1={r1:04b} => r2={result:04b}  C={carry}"
            lcd.clear()
            lcd.putstr(result_str)
            display_registers(r0, r1, result, carry)
            utime.sleep(0.5) 


timer = Timer(freq=1, mode=Timer.PERIODIC, callback=display_results)