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）
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#!/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 5×7 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
![LCD显示GPS时钟[嵌入式系统]](https://img.zhankr.net/50hizjq1bo345083.jpg)
