树莓派一般运行Linux操作系统后通过远程控制来运行，但是往往由于网络原因导致树莓派分配的ip地址被改变，致使需要重新连接屏幕后才能查看树莓派的当前ip。最近手头有个LCD1602，所以尝试将通过驱动LCD屏，使用Python获取到相关网卡的ip，再循环显示到屏幕上。如下为主要的代码，已经通过了测试。

#!/usr/bin/python3
#import
import RPi.GPIO as GPIO
import time
import socket
import fcntl
import struct
# Define GPIO to LCD mapping
LCD_RS = 7
LCD_E  = 8
LCD_D4 = 25
LCD_D5 = 24
LCD_D6 = 23
LCD_D7 = 18

def get_host_ip():
    try:
        s = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
        s.connect(('8.8.8.8',80))
        ip = s.getsockname()[0]
    finally:
        s.close()
    return ip
# Define some device constants
LCD_WIDTH = 16    # Maximum characters per line
LCD_CHR = True
LCD_CMD = False

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line

# Timing constants
#E_PULSE = 0.0005
#E_DELAY = 0.0005
E_PULSE = 0.001
E_DELAY = 0.001


def get_ip_address(ifname):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    return socket.inet_ntoa(fcntl.ioctl(
            s.fileno(),
            0x8915,  # SIOCGIFADDR
            struct.pack('256s', bytes(ifname[:15],'utf-8'))
    )[20:24])
def main():
    # Main program block
  GPIO.setwarnings(False)
  GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
  GPIO.setup(LCD_E, GPIO.OUT)  # E
  GPIO.setup(LCD_RS, GPIO.OUT) # RS
  GPIO.setup(LCD_D4, GPIO.OUT) # DB4
  GPIO.setup(LCD_D5, GPIO.OUT) # DB5
  GPIO.setup(LCD_D6, GPIO.OUT) # DB6
  GPIO.setup(LCD_D7, GPIO.OUT) # DB7
  time.sleep(15)

  # Initialise display
  lcd_init()
  ip1 = get_ip_address('wlan0')
  ip2 = get_ip_address('eth0')
  count = 0;
  while True:
    lcd_string("wlan0:",LCD_LINE_1)
    lcd_string(ip1,LCD_LINE_2)
    time.sleep(2)
    lcd_string("eth0:",LCD_LINE_1)
    lcd_string(ip2,LCD_LINE_2)
    time.sleep(2)
    count += 1
    if count == 10:
        lcd_clr()
        get_ip(ip1,ip2)
        count = 0
def lcd_clr():
    lcd_byte(0x01,LCD_CMD)
    lcd_byte(0x06,LCD_CMD)
    time.sleep(1)
def get_ip(ip1,ip2):
    ip1 = get_ip_address('wlan0')
    ip2 = get_ip_address('eth0')


def lcd_init():
    # Initialise display
  lcd_byte(0x33,LCD_CMD) # 110011 Initialise
  lcd_byte(0x32,LCD_CMD) # 110010 Initialise
  lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
  lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
  lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
  lcd_byte(0x01,LCD_CMD) # 000001 Clear display
  time.sleep(E_DELAY)

def lcd_byte(bits, mode):
    # Send byte to data pins
  # bits = data
  # mode = True  for character
  #        False for command

  GPIO.output(LCD_RS, mode) # RS

  # High bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x10==0x10:
      GPIO.output(LCD_D4, True)
  if bits&0x20==0x20:
      GPIO.output(LCD_D5, True)
  if bits&0x40==0x40:
      GPIO.output(LCD_D6, True)
  if bits&0x80==0x80:
      GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  lcd_toggle_enable()

  # Low bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x01==0x01:
      GPIO.output(LCD_D4, True)
  if bits&0x02==0x02:
      GPIO.output(LCD_D5, True)
  if bits&0x04==0x04:
      GPIO.output(LCD_D6, True)
  if bits&0x08==0x08:
      GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  lcd_toggle_enable()

def lcd_toggle_enable():
    # Toggle enable
  time.sleep(E_DELAY)
  GPIO.output(LCD_E, True)
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)
  time.sleep(E_DELAY)

def lcd_string(message,line):
    # Send string to display

  message = message.ljust(LCD_WIDTH," ")

  lcd_byte(line, LCD_CMD)

  for i in range(LCD_WIDTH):
      lcd_byte(ord(message[i]),LCD_CHR)

if __name__ == '__main__':

  try:
        main()
  except KeyboardInterrupt:
      pass
  finally:
    lcd_byte(0x01, LCD_CMD)
    lcd_string("Goodbye!",LCD_LINE_1)
    GPIO.cleanup()