夏任务102：做一个GPS钟

实验要求

　　用RPi的串口连接一个GPS模块，从GPS得到实时时间，在7段数码管或LCD上显示

实验工具：

Raspberry Pi Model B主机，

8G c10 SD卡，

USB充电线，

电源需自备5v 1A电源充电头一个

PC机一台（这里用的操作系统是windows7 64bit旗舰版）

LED面板

GPS模块+串口线

实验步骤：

连接电路线路

　　LCD连接参照blog：http://www.freemindworld.com/blog/2013/130310_raspberry_pi_with_lcd.shtml
　　GPS连接RPI

　　　　　　　　GPS板G3203:

　　　　　　　　　　VDD->RPi的3.3V

　　　　　　　　　　TXD->RPi的RXD

　　　　　　　　　　GND->RPi的GND

　　2。在树莓派上安装pyserial：

下载地址：http://sourceforge.net/projects/pyserial/files/pyserial/2.5/

解压后进入目录运行

  python setup.py install

编写代码Adafruit_CharLCD.py：

　　　　　　（LCD显示代码引自git clone https://github.com/lifanxi/rpimenu.git）

#!/usr/bin/python

# based on code from lrvick and LiquidCrystal

# lrvic - https://github.com/lrvick/raspi-hd44780/blob/master/hd44780.py

# LiquidCrystal - https://github.com/arduino/Arduino/blob/master/libraries/LiquidCrystal/LiquidCrystal.cpp

from time import sleep

import serial

import traceback

import os

import commands

import string

class Adafruit_CharLCD:

# commands

LCD_CLEARDISPLAY = 0x01

LCD_RETURNHOME = 0x02

LCD_ENTRYMODESET = 0x04

LCD_DISPLAYCONTROL = 0x08

LCD_CURSORSHIFT = 0x10

LCD_FUNCTIONSET = 0x20

LCD_SETCGRAMADDR = 0x40

LCD_SETDDRAMADDR = 0x80

# flags for display entry mode

LCD_ENTRYRIGHT = 0x00

LCD_ENTRYLEFT = 0x02

LCD_ENTRYSHIFTINCREMENT = 0x01

LCD_ENTRYSHIFTDECREMENT = 0x00

# flags for display on/off control

LCD_DISPLAYON = 0x04

LCD_DISPLAYOFF = 0x00

LCD_CURSORON = 0x02

LCD_CURSOROFF = 0x00

LCD_BLINKON = 0x01

LCD_BLINKOFF = 0x00

# flags for display/cursor shift

LCD_DISPLAYMOVE = 0x08

LCD_CURSORMOVE = 0x00

# flags for display/cursor shift

LCD_DISPLAYMOVE = 0x08

LCD_CURSORMOVE = 0x00

LCD_MOVERIGHT = 0x04

LCD_MOVELEFT = 0x00

# flags for function set

LCD_8BITMODE = 0x10

LCD_4BITMODE = 0x00

LCD_2LINE = 0x08

LCD_1LINE = 0x00

LCD_5x10DOTS = 0x04

LCD_5x8DOTS = 0x00

def show_time(i,interval):

global num

while True:

try:

show(num)

except Exception as ep:

print ep

def __init__(self, pin_rs=4, pin_e=25, pins_db=[17, 18, 27, 22], GPIO = None):

# Emulate the old behavior of using RPi.GPIO if we haven't been given

# an explicit GPIO interface to use

if not GPIO:

import RPi.GPIO as GPIO

self.GPIO = GPIO

self.pin_rs = pin_rs

self.pin_e = pin_e

self.pins_db = pins_db

self.GPIO.setmode(GPIO.BCM)

self.GPIO.setup(self.pin_e, GPIO.OUT)

self.GPIO.setup(self.pin_rs, GPIO.OUT)

for pin in self.pins_db:

self.GPIO.setup(pin, GPIO.OUT)

self.write4bits(0x33) # initialization

self.write4bits(0x32) # initialization

self.write4bits(0x28) # 2 line 5x7 matrix

self.write4bits(0x0C) # turn cursor off 0x0E to enable cursor

self.write4bits(0x06) # shift cursor right

self.displaycontrol = self.LCD_DISPLAYON | self.LCD_CURSOROFF | self.LCD_BLINKOFF

self.displayfunction = self.LCD_4BITMODE | self.LCD_1LINE | self.LCD_5x8DOTS

self.displayfunction |= self.LCD_2LINE

""" Initialize to default text direction (for romance languages) """

self.displaymode = self.LCD_ENTRYLEFT | self.LCD_ENTRYSHIFTDECREMENT

self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) # set the entry mode

self.clear()

def begin(self, cols, lines):

if (lines > 1):

self.numlines = lines

self.displayfunction |= self.LCD_2LINE

self.currline = 0

def home(self):

self.write4bits(self.LCD_RETURNHOME) # set cursor position to zero

self.delayMicroseconds(3000) # this command takes a long time!

def clear(self):

self.write4bits(self.LCD_CLEARDISPLAY) # command to clear display

self.delayMicroseconds(3000) # 3000 microsecond sleep, clearing the display takes a long time

def setCursor(self, col, row):

self.row_offsets = [ 0x00, 0x40, 0x14, 0x54 ]

if ( row > self.numlines ):

row = self.numlines - 1 # we count rows starting w/0

self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row]))

def noDisplay(self):

""" Turn the display off (quickly) """

self.displaycontrol &= ~self.LCD_DISPLAYON