树莓派4B直插LCD 1602a实践

(Updated: )
树莓派
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LCD1602a显示效果

找出来吃灰多年的 LCD 1602a 液晶屏，记得之前用树莓派 3B 驱动过，那时没做记录全都忘记了，今天用树莓派 4B 直插 LCD 1602a 看看效果。
网上的资料很多都是使用 I2C 方式驱动，需要 I2C 模块，好处是接线与配置都简单，而我穷的没有。。。

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LCD 1602a 拥有单行显示 16 个字符，总共两行显示空间（所以叫 1602），
在一些显示规格要求不高的场景应用还是很多的。

1. 准备清单

  1. 树莓派 4B
  2. LCD 1602a
  3. 面包板
  4. 杜邦线几根

2. 人家的接线方式

**LCD 针脚** **说明** **接线** **树莓派针脚**
01 VSS (GND) Breadboard GND（面包板接地）
02 VDD (+5v) Breadboard +5v（面包板5V）
03 VO (Contrast，显示对比度调整) Middle Pin Trimmer（接电位器中间线）
04 RS GPIO7 26
05 RW Breadboard GND
06 E GPIO8 24
07 D0
08 D1
09 D2
10 D3
11 D4 GPIO25 22
12 D5 GPIO24 18
13 D6 GPIO23 16
14 D7 GPIO18 12
15 A (+5V) Breadboard +5v
16 K (GND) Breadboard GND

参考的接线图

参考的LCD接线图

3. 我的接线方式

既然提到了电位器，我依然没有，但是电位器不就是可调电阻吗，资料上说接5V然后调整，那我直接供3.3V行不行呢？

这是我的接线图

**LCD 针脚** **说明** **接线** **树莓派针脚**
01 VSS (GND) Breadboard GND（面包板接地）
02 VDD (+5v) Breadboard +3.3V（面包板3.3V）
03 VO (Contrast) Breadboard GND（面包板接地，与3.3V）
04 RS GPIO7 26
05 RW Breadboard GND
06 E GPIO8 24
07 D0
08 D1
09 D2
10 D3
11 D4 GPIO25 22
12 D5 GPIO24 18
13 D6 GPIO23 16
14 D7 GPIO18 12
15 A (+5V) Breadboard +5v
16 K (GND) Breadboard GND 
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本来想用Fritzing画一下我的接线方式，怎知Fritzing元件库里竟然没有树莓派4B。。
那就只好来个凌乱一点的手机照了

我的接线实物图

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123就对应的VSS VDD VO，接到了3.3v与GND，其他都一样，
是为了控制显示对比度，调太高的话看不清，太低的话看不清，
那我这里直接给个固定值

4. Python 编程

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#  MBTechWorks.com 2016
#  Control an LCD 1602 display from Raspberry Pi with Python programming

#!/usr/bin/python

# Pinout of the LCD:
# 1 : GND
# 2 : 5V power
# 3 : Display contrast    - Connect to middle pin potentiometer   
# 4 : RS (Register Select)
# 5 : R/W (Read Write)    - Ground this pin (important)
# 6 : Enable or Strobe
# 7 : Data Bit 0          - data pin 0, 1, 2, 3 are not used
# 8 : Data Bit 1          -   
# 9 : Data Bit 2          -   
# 10: Data Bit 3          -   
# 11: Data Bit 4
# 12: Data Bit 5
# 13: Data Bit 6
# 14: Data Bit 7
# 15: LCD Backlight +5V
# 16: LCD Backlight GND

import RPi.GPIO as GPIO
import time

# GPIO to LCD mapping
LCD_RS = 7   # Pi pin 26
LCD_E  = 8   # Pi pin 24
LCD_D4 = 25  # Pi pin 22
LCD_D5 = 24  # Pi pin 18
LCD_D6 = 23  # Pi pin 16
LCD_D7 = 18  # Pi pin 12

# Device constants
LCD_CHR = True    # Character mode
LCD_CMD = False   # Command mode
LCD_CHARS = 16    # Characters per line (16 max)
LCD_LINE_1 = 0x80 # LCD memory location for 1st line
LCD_LINE_2 = 0xC0 # LCD memory location 2nd line

# Define main program code
def main():
  
  GPIO.setwarnings(False)
  GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
  GPIO.setup(LCD_E, GPIO.OUT)  # Set GPIO's to output mode
  GPIO.setup(LCD_RS, GPIO.OUT)
  GPIO.setup(LCD_D4, GPIO.OUT)
  GPIO.setup(LCD_D5, GPIO.OUT)
  GPIO.setup(LCD_D6, GPIO.OUT)
  GPIO.setup(LCD_D7, GPIO.OUT)

# Initialize display
  lcd_init()

# Loop - send text and sleep 3 seconds between texts
# Change text to anything you wish, but must be 16 characters or less

  while True:
    lcd_text("Hello World!",LCD_LINE_1)
    lcd_text("",LCD_LINE_2)

    lcd_text("Rasbperry Pi",LCD_LINE_1)
    lcd_text("16x2 LCD Display",LCD_LINE_2)

    time.sleep(2) # 3 second delay

    lcd_text("ABCDEFGHIJKLMNOP",LCD_LINE_1)
    lcd_text("1234567890123456",LCD_LINE_2)

    time.sleep(2) # 3 second delay

    lcd_text("I love my",LCD_LINE_1)
    lcd_text("Raspberry Pi!",LCD_LINE_2)

    time.sleep(2)

    lcd_text("lison.cc",LCD_LINE_1)
    lcd_text("For more R Pi",LCD_LINE_2)

    time.sleep(2)

# End of main program code


# Initialize and clear display
def lcd_init():
  lcd_write(0x33,LCD_CMD) # Initialize
  lcd_write(0x32,LCD_CMD) # Set to 4-bit mode
  lcd_write(0x06,LCD_CMD) # Cursor move direction
  lcd_write(0x0C,LCD_CMD) # Turn cursor off
  lcd_write(0x28,LCD_CMD) # 2 line display
  lcd_write(0x01,LCD_CMD) # Clear display
  time.sleep(0.0005)     # Delay to allow commands to process

def lcd_write(bits, mode):
# High bits
  GPIO.output(LCD_RS, mode) # RS

  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x10==0x10:
    GPIO.output(LCD_D4, True)
  if bits&0x20==0x20:
    GPIO.output(LCD_D5, True)
  if bits&0x40==0x40:
    GPIO.output(LCD_D6, True)
  if bits&0x80==0x80:
    GPIO.output(LCD_D7, True)

# Toggle 'Enable' pin
  lcd_toggle_enable()

# Low bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x01==0x01:
    GPIO.output(LCD_D4, True)
  if bits&0x02==0x02:
    GPIO.output(LCD_D5, True)
  if bits&0x04==0x04:
    GPIO.output(LCD_D6, True)
  if bits&0x08==0x08:
    GPIO.output(LCD_D7, True)

# Toggle 'Enable' pin
  lcd_toggle_enable()

def lcd_toggle_enable():
  time.sleep(0.0005)
  GPIO.output(LCD_E, True)
  time.sleep(0.0005)
  GPIO.output(LCD_E, False)
  time.sleep(0.0005)

def lcd_text(message,line):
  # Send text to display
  message = message.ljust(LCD_CHARS," ")

  lcd_write(line, LCD_CMD)

  for i in range(LCD_CHARS):
    lcd_write(ord(message[i]),LCD_CHR)


#Begin program
try:
  main()
	  
except KeyboardInterrupt:
  pass
	
finally:
  lcd_write(0x01, LCD_CMD)
  lcd_text("So long!",LCD_LINE_1)
  lcd_text("lison.cc",LCD_LINE_2)
  GPIO.cleanup()
# MBTechWorks.com 2016
# Control an LCD 1602 display from Raspberry Pi with Python programming

#!/usr/bin/python

# Pinout of the LCD:
# 1 : GND
# 2 : 5V power
# 3 : Display contrast - Connect to middle pin potentiometer 
# 4 : RS (Register Select)
# 5 : R/W (Read Write) - Ground this pin (important)
# 6 : Enable or Strobe
# 7 : Data Bit 0 - data pin 0, 1, 2, 3 are not used
# 8 : Data Bit 1 - 
# 9 : Data Bit 2 - 
# 10: Data Bit 3 - 
# 11: Data Bit 4
# 12: Data Bit 5
# 13: Data Bit 6
# 14: Data Bit 7
# 15: LCD Backlight +5V
# 16: LCD Backlight GND

import RPi.GPIO as GPIO
import time

# GPIO to LCD mapping
LCD_RS = 7 # Pi pin 26
LCD_E = 8 # Pi pin 24
LCD_D4 = 25 # Pi pin 22
LCD_D5 = 24 # Pi pin 18
LCD_D6 = 23 # Pi pin 16
LCD_D7 = 18 # Pi pin 12

# Device constants
LCD_CHR = True # Character mode
LCD_CMD = False # Command mode
LCD_CHARS = 16 # Characters per line (16 max)
LCD_LINE_1 = 0x80 # LCD memory location for 1st line
LCD_LINE_2 = 0xC0 # LCD memory location 2nd line

# Define main program code
def main():
 
 GPIO.setwarnings(False)
 GPIO.setmode(GPIO.BCM) # Use BCM GPIO numbers
 GPIO.setup(LCD_E, GPIO.OUT) # Set GPIO's to output mode
 GPIO.setup(LCD_RS, GPIO.OUT)
 GPIO.setup(LCD_D4, GPIO.OUT)
 GPIO.setup(LCD_D5, GPIO.OUT)
 GPIO.setup(LCD_D6, GPIO.OUT)
 GPIO.setup(LCD_D7, GPIO.OUT)

# Initialize display
 lcd_init()

# Loop - send text and sleep 3 seconds between texts
# Change text to anything you wish, but must be 16 characters or less

 while True:
 lcd_text("Hello World!",LCD_LINE_1)
 lcd_text("",LCD_LINE_2)

 lcd_text("Rasbperry Pi",LCD_LINE_1)
 lcd_text("16x2 LCD Display",LCD_LINE_2)

 time.sleep(3) # 3 second delay

 lcd_text("ABCDEFGHIJKLMNOP",LCD_LINE_1)
 lcd_text("1234567890123456",LCD_LINE_2)

 time.sleep(3) # 3 second delay

 lcd_text("I love my",LCD_LINE_1)
 lcd_text("Raspberry Pi!",LCD_LINE_2)

 time.sleep(3)

 lcd_text("lison.cc",LCD_LINE_1)
 lcd_text("For more R Pi",LCD_LINE_2)

 time.sleep(3)

# End of main program code


# Initialize and clear display
def lcd_init():
 lcd_write(0x33,LCD_CMD) # Initialize
 lcd_write(0x32,LCD_CMD) # Set to 4-bit mode
 lcd_write(0x06,LCD_CMD) # Cursor move direction
 lcd_write(0x0C,LCD_CMD) # Turn cursor off
 lcd_write(0x28,LCD_CMD) # 2 line display
 lcd_write(0x01,LCD_CMD) # Clear display
 time.sleep(0.0005) # Delay to allow commands to process

def lcd_write(bits, mode):
# High bits
 GPIO.output(LCD_RS, mode) # RS

 GPIO.output(LCD_D4, False)
 GPIO.output(LCD_D5, False)
 GPIO.output(LCD_D6, False)
 GPIO.output(LCD_D7, False)
 if bits&0x10==0x10:
 GPIO.output(LCD_D4, True)
 if bits&0x20==0x20:
 GPIO.output(LCD_D5, True)
 if bits&0x40==0x40:
 GPIO.output(LCD_D6, True)
 if bits&0x80==0x80:
 GPIO.output(LCD_D7, True)

# Toggle 'Enable' pin
 lcd_toggle_enable()

# Low bits
 GPIO.output(LCD_D4, False)
 GPIO.output(LCD_D5, False)
 GPIO.output(LCD_D6, False)
 GPIO.output(LCD_D7, False)
 if bits&0x01==0x01:
 GPIO.output(LCD_D4, True)
 if bits&0x02==0x02:
 GPIO.output(LCD_D5, True)
 if bits&0x04==0x04:
 GPIO.output(LCD_D6, True)
 if bits&0x08==0x08:
 GPIO.output(LCD_D7, True)

# Toggle 'Enable' pin
 lcd_toggle_enable()

def lcd_toggle_enable():
 time.sleep(0.0005)
 GPIO.output(LCD_E, True)
 time.sleep(0.0005)
 GPIO.output(LCD_E, False)
 time.sleep(0.0005)

def lcd_text(message,line):
 # Send text to display
 message = message.ljust(LCD_CHARS," ")

 lcd_write(line, LCD_CMD)

 for i in range(LCD_CHARS):
 lcd_write(ord(message[i]),LCD_CHR)


#Begin program
try:
 main()
 
except KeyboardInterrupt:
 pass
 
finally:
 lcd_write(0x01, LCD_CMD)
 lcd_text("So long!",LCD_LINE_1)
 lcd_text("lison.cc",LCD_LINE_2)
 GPIO.cleanup()

5. 另外

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如何查看自己的树莓派pin与gpio对应关系，终端输入pinout，打印如下图

树莓派打印pinout

参考资料