手頭有一塊 LCD1602顯示屏，於是嘗試着用樹莓派控制它的顯示。網上直接找到現成的例子，操作成功，在此記錄。
樹莓派版本：Model 3B+
樹莓派系統：Raspbian Stretch with desktop and recommended software，April 2019
參考資料：《樹莓派+LCD1602實現系統監控: IP/時鍾/溫度/內存》。
在樹莓派電源關閉時，根據參考資料中的連接方式（截圖如下）連接樹莓派、LCD顯示屏和電位器，因為很多引腳需要連接正負極，樹莓派上沒有足夠多的5v，所以我用了一個面包板。
連接好后如下圖所示。我的線太長了，顯得有些亂，大家接線的時候小心短路。
樹莓派開機。
LCD 顯示屏就會亮，但沒有顯示內容。
將參考資料中的兩個 python 文件保存至樹莓派中的同一文件夾下，長文件命名為1602led.py，短文件命名為1602.py。代碼如下，點擊+展開：
#!/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 class 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)
代碼需用 python2.7 運行，終端進入對應的文件夾下，執行 python 1602.py ，就能發現顯示屏變化了。注意，可能需要旋轉電位器轉軸來矯正顯示屏。
運行結果：
該程序是無限循環的，終止程序后（control+C），顯示屏會保留最后狀態。
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