手头有一块 LCD1602显示屏，于是尝试着用树莓派控制它的显示。网上直接找到现成的例子，操作成功，在此记录。

 

树莓派版本：Model 3B+

树莓派系统：Raspbian Stretch with desktop and recommended software，April 2019

参考资料：《》。

在树莓派电源关闭时，根据参考资料中的连接方式（截图如下）连接树莓派、LCD显示屏和电位器，因为很多引脚需要连接正负极，树莓派上没有足够多的5v，所以我用了一个面包板。

连接好后如下图所示。我的线太长了，显得有些乱，大家接线的时候小心短路。

树莓派开机。

LCD 显示屏就会亮，但没有显示内容。

将参考资料中的两个 python 文件保存至树莓派中的同一文件夹下，长文件命名为1602led.py，短文件命名为1602.py。代码如下，点击+展开：

#!/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 sleepclass lcd1602:    # 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.setwarnings(False)        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 = lcd1602()    lcd.clear()    lcd.message("hello world!")

#!/usr/bin/python from lcd1602 import *from datetime import *import commands def get_cpu_temp():    tmp = open('/sys/class/thermal/thermal_zone0/temp')    cpu = tmp.read()    tmp.close()    return '{:.2f}'.format( float(cpu)/1000 ) + ' C' def get_gpu_temp():    tmp = commands.getoutput('vcgencmd measure_temp|awk -F= \'{print $2}\'').replace('\'C','')    gpu = float(tmp)    return '{:.2f}'.format( gpu ) + ' C' def get_time_now():    return datetime.now().strftime('    %H:%M:%S\n   %Y-%m-%d') def get_ip_info():    return commands.getoutput('ifconfig wlan0|grep inet|awk -Faddr: \'{print $2}\'|awk \'{print $1}\'') def get_mem_info():    total= commands.getoutput('free -m|grep Mem:|awk \'{print $2}\'')      free = commands.getoutput('free -m|grep cache:|awk \'{print $4}\'')    return 'MEM:\n    ' + free +' / '+ total +' M' lcd = lcd1602()lcd.clear() if __name__ == '__main__':     while(1):        lcd.clear()        lcd.message( get_ip_info() )        sleep(5)                 lcd.clear()        lcd.message( get_time_now() )        sleep(5)                 lcd.clear()        lcd.message( get_mem_info() )        sleep(5)         lcd.clear()        lcd.message( 'CPU: ' + get_cpu_temp()+'\n' )        lcd.message( 'GPU: ' + get_gpu_temp() )        sleep(5)

代码需用 python2.7 运行，终端进入对应的文件夹下，执行 python 1602.py ，就能发现显示屏变化了。注意，可能需要旋转电位器转轴来矫正显示屏。

运行结果：

 

该程序是无限循环的，终止程序后（control+C），显示屏会保留最后状态。

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