开拖拉机的熊猫

夏任务103：做一个网络时钟

浙江大学计算机科学与技术学院 / 课程：嵌入式系统 / 指导教师：翁恺

做一个网络时钟，通过ntp从一个互联网服务器得到时间，实时在7段数码管或LCD上显示时间

先决条件：完成任务16：配置ntp客户端

1.       焊接LCD1602

略……嗯……我不是在卖萌，而是因为……之前买过一块Sparten-3E的板子（就是和体系实验用的一样的板子）然后刚好有一块已经焊好的1602的屏，就直接拆下来拿过来用了^_^而且是块蓝屏，我喜欢的颜色~

2.       连接LCD1602与树莓派

LCD1602液晶屏提供了16列x2行的ASCII字符显示能力，工作电压5V，提供4位数据与8位数据两种工作模式，Raspberry Pi的GPIO口数量很有限，所以我们使用4位数据模式。

LCD1602液晶屏模块提供了16个引脚，我们只需接其中的12个即可：

1)         VSS，接地，RPi PIN 6

2)         VDD，接5V电源，PRi PIN 2

3)         VO，液晶对比度调节，接电位器中间的引脚

4)         RS，寄存器选择，接GPIO 14，RPi PIN 8

5)         RW，读写选择，接地，表示写模式，PRi PIN 6

6)         EN，使能信号，接GPIO 15，RPi PIN 10

7)         D0，数据位0，4位工作模式下不用，不接

8)         D1，数据位1，4位工作模式下不用，不接

9)         D2，数据位2，4位工作模式下不用，不接

10)     D3，数据位3，4位工作模式下不用，不接

11)     D4，数据位4，接GPIO 17，RPi PIN 11

12)     D5，数据位5，接GPIO 18，RPi PIN 12

13)     D6，数据位6，接GPIO 27，RPi PIN 13

14)     D7，数据位7，接GPIO 22，RPi PIN 15

15)     A，液晶屏背光+，接5V，RPi PIN 2

16)     K，液晶屏背光-，接地，RPi PIN 6

注意：

u  请注意GIPO引脚编号与Raspberry Pi上P1扩展口的PIN编号的区别，别搞混了。

u  如果你的液晶屏没有背光，则15,16脚可能不会引出，也就不用接线。

u  LCD1602工作电压是5V，而RPi的GPIO口工作电压是3.3V，所以RW脚请确保接地进入写模式，否则尝试从LCD1602读取数据可能会烧掉RPi。

u  VO脚接的是电位器，电位器的另外两个脚分别接5V和地。通过调节这个电位器，可以调节液晶屏的对比度。

u  Raspberry Pi有Rev 1和Rev 2两个版本，它们对于PIN 13的定义是不同的。市面上现在大部分都是Rev 2版本，PIN 13对应GPIO 27。如果你的RPi是老的Rev 1版本，PIN 13对应是GPIO 21，你需要调整程序中的参数，把27改为21。

3.       显示时间日期

驱动LCD1602

wget https://raw.github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/master/Adafruit_CharLCD/Adafruit_CharLCD.py

显示时间的python脚本clock.py

nano clock.py

贴入以下内容（基于https://raw.github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/master/Adafruit_CharLCD/Adafruit_CharLCD_IPclock_example.py修改）

#!/usr/bin/python from Adafruit_CharLCD import Adafruit_CharLCD from subprocess import * from time import sleep, strftime from datetime import datetime lcd = Adafruit_CharLCD() lcd.begin(16,1) while 1:         lcd.clear()         lcd.message(datetime.now().strftime(‘%Y %b %d %a\n  %H : %M : %S’))         sleep(1)

执行脚本

sudo python clock.py

效果如图：

当然也可以直接用一个脚本来完成这件事：

#!/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 from datetime import datetime 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 __init__(self, pin_rs=14, pin_e=15, 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() lcd.noBlink() while True: sleep(1) lcd.clear() lcd.message(datetime.now().strftime(' %H : %M : %S \n%b %d %Y %a')) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 #!/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 from datetime import datetime   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 __init__(self, pin_rs=14, pin_e=15, 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()     lcd.noBlink()       while True:         sleep(1)         lcd.clear()         lcd.message(datetime.now().strftime('  %H : %M : %S \n%b %d %Y %a'))

4. 写在后面

这个接线真是接的我头昏眼花，我必须得说，在做这个任务的时候我最大的愿望就是……我能把那一排杜邦线和面包线撕开一根一根用或者几根几根用……这一排在一起接真是要人命的！

 

Acknowledgement

http://www.freemindworld.com/blog/2013/130310_raspberry_pi_with_lcd.shtml

http://hugozhu.myalert.info/2013/03/23/19-raspberry-pi-drive-1602-lcd.html

http://learn.adafruit.com/drive-a-16×2-lcd-directly-with-a-raspberry-pi/wiring