"""Program 4-5: Loopback test. Explore the readline() function.
           Put a jumper between the GP21 pin and the GP20 pin.
"""

import time
from machine import UART, Pin

uart1 = UART(1, baudrate = 9600, rx = Pin(21), tx = Pin(20))
m = uart1.write("ABCDEFGHIJKLMNO\nPQRSTUVWXYZ")
time.sleep_ms(30)
n = uart1.readline()
print (m, n)
p = uart1.readline()
print (p)