LCD显示GPS时钟[嵌入式系统]

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：

1. 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

　　

1. 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

self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

def display(self):

""" Turn the display on (quickly) """

self.displaycontrol |= self.LCD_DISPLAYON

self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

def noCursor(self):

""" Turns the underline cursor on/off """

self.displaycontrol &= ~self.LCD_CURSORON

self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

def cursor(self):

""" Cursor On """

self.displaycontrol |= self.LCD_CURSORON

self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

def noBlink(self):

""" Turn on and off the blinking cursor """

self.displaycontrol &= ~self.LCD_BLINKON

self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

def noBlink(self):

""" Turn on and off the blinking cursor """

self.displaycontrol &= ~self.LCD_BLINKON

self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)

def DisplayLeft(self):

""" These commands scroll the display without changing the RAM """

self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT)

def scrollDisplayRight(self):

""" These commands scroll the display without changing the RAM """

self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT);

def leftToRight(self):

""" This is for text that flows Left to Right """

self.displaymode |= self.LCD_ENTRYLEFT

self.write4bits(self.LCD_ENTRYMODESET | self.displaymode);

def rightToLeft(self):

""" This is for text that flows Right to Left """

self.displaymode &= ~self.LCD_ENTRYLEFT

self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)

def autoscroll(self):

""" This will 'right justify' text from the cursor """

self.displaymode |= self.LCD_ENTRYSHIFTINCREMENT

self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)

def noAutoscroll(self):

""" This will 'left justify' text from the cursor """

self.displaymode &= ~self.LCD_ENTRYSHIFTINCREMENT

self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)

def write4bits(self, bits, char_mode=False):

""" Send command to LCD """

self.delayMicroseconds(1000) # 1000 microsecond sleep

bits=bin(bits)[2:].zfill(8)

self.GPIO.output(self.pin_rs, char_mode)

for pin in self.pins_db:

self.GPIO.output(pin, False)

for i in range(4):

if bits[i] == "1":

self.GPIO.output(self.pins_db[::-1][i], True)

self.pulseEnable()

for pin in self.pins_db:

self.GPIO.output(pin, False)

for i in range(4,8):

if bits[i] == "1":

self.GPIO.output(self.pins_db[::-1][i-4], True)

self.pulseEnable()

def delayMicroseconds(self, microseconds):

seconds = microseconds / float(1000000)    # divide microseconds by 1 million for seconds

sleep(seconds)

def pulseEnable(self):

self.GPIO.output(self.pin_e, False)

self.delayMicroseconds(1)              # 1 microsecond pause - enable pulse must be > 450ns

self.GPIO.output(self.pin_e, True)

self.delayMicroseconds(1)              # 1 microsecond pause - enable pulse must be > 450ns

self.GPIO.output(self.pin_e, False)

self.delayMicroseconds(1)              # commands need > 37us to settle

def message(self, text):

""" Send string to LCD. Newline wraps to second line"""

for char in text:

if char == '\n':

self.write4bits(0xC0) # next line

else:

self.write4bits(ord(char),True)

if __name__ == '__main__':

lcd = Adafruit_CharLCD()

mest="Lab102 GPS Clock \n time: "

　　message="show"

while True:

try:

tmp=ser.readline()

if tmp.find('GPRMC')==1:

buf = tmp.split(',')

tim = buf[1]

print tim

num = tim[0:8]

message= mest+num

lcd.clear()

lcd.message(message)

except Exception as e:

print e

#ser.close()

ser = serial.Serial('/dev/ttyAMA0')

　　　　　　3.SSH连接树莓派，运行该代码,LCD显示如图：

　　　　　　　　

sudo python Adafruit_CharLCD.py