serial_write.py

# serial_write.py
import serial, time

SERIALPORT = "/dev/ttyS0"
ser = serial.Serial(SERIALPORT, baudrate=115200, bytesize=8, parity="N", stopbits=1, rtscts=False, xonxoff=False)

def write_data():
    while True:
        txt = input("input some thing ...\r\n")
        if txt.startswith("exit"):
            break
        print(txt)
        ser.write(bytearray(txt.strip().encode()) + b'\r\n')

    print("bye!")

if __name__ == '__main__':
    print(ser)
    print("write data")
    write_data()