标签：液晶屏
为利用学习单片机时留下的1602lcd，在树莓派下尝试使用，查找资料时发现了李凡希大神的博客早有记载，故利用他的实验代码，仿照搭建了下。其博客原地址为：https://www.freemindworld.com/blog/2013/130310_raspberry_pi_with_lcd.shtml
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：
1.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。
2.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。
3.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。
4.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。
5.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。
以上基本沿用
代码如下：
#!/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 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.clear()
lcd.message(" LCD 1602 Test \n123456789ABCDEF")标签：液晶屏
原文地址：http://mayuenjkxt.blog.51cto.com/2676799/1858978
