Pi Use RX/TX

import serial, time
import RPi.GPIO as GPIO


GPIO.setmode(GPIO.BCM)
GPIO.setup(4, GPIO.OUT)

a=GPIO.PWM(4,50)
a.start(5)

piw = serial.Serial('/dev/ttyAMA0', 115200, timeout=1)

piw.open()

try:
        while 1:
                response = 'no'
                response = piw.readline()
                if response == 'pi':
                        a.ChangeDutyCycle(99)
                        print'ON'+response
                else:
                        a.ChangeDutyCycle(0)
                        print'off'+response
except KeyboardInterrupt:
    piw.close()

https://github.com/lurch/rpi-serial-console

sudo rpi-serial-console disable

關掉才能傳輸

參考:
http://pyserial.sourceforge.net/shortintro.html
https://mail.python.org/pipermail/python-list/2009-October/555361.html