python 程序 lcd 20x4 显示器是否需要使用 RPi GPIO 08 引脚？

Question

我创建了一个 python 程序，使用 wxpython 模块来显示 mcp3008 的输出，它将来自雨水传感器的数据从模拟转换为数字。我正在做的这个项目是升级当前项目，仅通过来自其他输入或源的 lcd 20x4 显示器显示数据。但是我的wxpython 程序使用了GPIO08 引脚，该引脚具有用于SPI 总线的SPIO_CE0_N 功能，因为我的mcp3008 要求它检查我的其他spi 引脚。这是我的树莓派 mcp3008 引脚布局：

VDD   3.3V
VREF  3.3V
AGND  GROUND
CLK   GPIO11 (P1-23)
DOUT  GPIO9  (P1-21)
DIN   GPIO10 (P1-19)
CS    GPIO8  (P1-24)
DGND  GROUND

这是树莓派的 lcd 20x4 显示引脚布局：

LCD Pin Function    Pi Function Pi Pin
01  GND GND P1-06
02  +5V +5V P1-02
03  Contrast        
04  RS  GPIO7   P1-26
05  RW  GND P1-06
06  E   GPIO8   P1-24
07  Data 0      
08  Data 1      
09  Data 2      
10  Data 3      
11  Data 4  GPIO25  P1-22
12  Data 5  GPIO24  P1-18
13  Data 6  GPIO23  P1-16
14  Data 7  GPIO18  P1-12
15  +5V via 560 ohm     
16  GND     P1-06

作为我从互联网上获得的用于液晶显示器的python程序，在程序中使用GPIO 08：

#!/usr/bin/python
#--------------------------------------
#    ___  ___  _ ____
#   / _ \/ _ \(_) __/__  __ __
#  / , _/ ___/ /\ \/ _ \/ // /
# /_/|_/_/  /_/___/ .__/\_, /
#                /_/   /___/
#
#  lcd_16x2.py
#  20x4 LCD Test Script with
#  backlight control and text justification
#
# Author : Matt Hawkins
# Date   : 06/04/2015
#
# http://www.raspberrypi-spy.co.uk/
#
#--------------------------------------

# The wiring for the LCD is as follows:
# 1 : GND
# 2 : 5V
# 3 : Contrast (0-5V)*
# 4 : RS (Register Select)
# 5 : R/W (Read Write)       - GROUND THIS PIN
# 6 : Enable or Strobe
# 7 : Data Bit 0             - NOT USED
# 8 : Data Bit 1             - NOT USED
# 9 : Data Bit 2             - NOT USED
# 10: Data Bit 3             - NOT USED
# 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
import RPi.GPIO as GPIO
import time

# Define GPIO to LCD mapping
LCD_RS = 7
LCD_E  = 8
LCD_D4 = 25
LCD_D5 = 24
LCD_D6 = 23
LCD_D7 = 18
LED_ON = 15

# Define some device constants
LCD_WIDTH = 20    # Maximum characters per line
LCD_CHR = True
LCD_CMD = False

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line

# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005

def main():
  # Main program block

  GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
  GPIO.setup(LCD_E, GPIO.OUT)  # E
  GPIO.setup(LCD_RS, GPIO.OUT) # RS
  GPIO.setup(LCD_D4, GPIO.OUT) # DB4
  GPIO.setup(LCD_D5, GPIO.OUT) # DB5
  GPIO.setup(LCD_D6, GPIO.OUT) # DB6
  GPIO.setup(LCD_D7, GPIO.OUT) # DB7
  GPIO.setup(LED_ON, GPIO.OUT) # Backlight enable

  # Initialise display
  lcd_init()

  # Toggle backlight on-off-on
  lcd_backlight(True)
  time.sleep(0.5)
  lcd_backlight(False)
  time.sleep(0.5)
  lcd_backlight(True)
  time.sleep(0.5)

  while True:

    # Send some centred test
    lcd_string("--------------------",LCD_LINE_1,2)
    lcd_string("Rasbperry Pi",LCD_LINE_2,2)
    lcd_string("Model B",LCD_LINE_3,2)
    lcd_string("--------------------",LCD_LINE_4,2)

    time.sleep(3) # 3 second delay

    lcd_string("Raspberrypi-spy",LCD_LINE_1,3)
    lcd_string(".co.uk",LCD_LINE_2,3)
    lcd_string("",LCD_LINE_3,2)
    lcd_string("20x4 LCD Module Test",LCD_LINE_4,2)

    time.sleep(3) # 20 second delay

    # Blank display
    lcd_byte(0x01, LCD_CMD)

    time.sleep(3) # 3 second delay

def lcd_init():
  # Initialise display
  lcd_byte(0x33,LCD_CMD) # 110011 Initialise
  lcd_byte(0x32,LCD_CMD) # 110010 Initialise
  lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
  lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
  lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
  lcd_byte(0x01,LCD_CMD) # 000001 Clear display
  time.sleep(E_DELAY)

def lcd_byte(bits, mode):
  # Send byte to data pins
  # bits = data
  # mode = True  for character
  #        False for command

  GPIO.output(LCD_RS, mode) # RS

  # High bits
  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():
  # Toggle enable
  time.sleep(E_DELAY)
  GPIO.output(LCD_E, True)
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)
  time.sleep(E_DELAY)

def lcd_string(message,line,style):
  # Send string to display
  # style=1 Left justified
  # style=2 Centred
  # style=3 Right justified

  if style==1:
    message = message.ljust(LCD_WIDTH," ")
  elif style==2:
    message = message.center(LCD_WIDTH," ")
  elif style==3:
    message = message.rjust(LCD_WIDTH," ")

  lcd_byte(line, LCD_CMD)

  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)

def lcd_backlight(flag):
  # Toggle backlight on-off-on
  GPIO.output(LED_ON, flag)

if __name__ == '__main__':

  try:
    main()
  except KeyboardInterrupt:
    pass
  finally:
    lcd_byte(0x01, LCD_CMD)
    lcd_string("Goodbye!",LCD_LINE_1,2)
    GPIO.cleanup()

所以我的问题是我可以将使用GPIO 08 的液晶显示器的针脚更改为其他针脚并更改程序以使用更改的 RPi 针脚，因为我不知道液晶显示器 python 程序是否需要使用 @ GPIO 08 中的 987654331@ 或仅使用 GPIO 08 而没有 SPIO_CE0_N 函数。

Answer 1

仅当您使用硬件 SPI 时，您才在 Raspberry Pi 上使用 GPIO 8 代替 SPI_CE0，并且从您的 MCP3008 连接来看，很明显您是。

最简单的解决方案是使用Software SPI 代替MCP3008，并将MCP3008 CLK、DOUT、DIN 和CS/SHDN 引脚连接到任何其他空闲的数字GPIO 引脚，并使用您的@ 987654334@ 用于 LCD 连接。或者您也可以反其道而行之，为您的 LCD 使用软件 SPI。

从硬件 SPI 切换到软件 SPI 很容易，您只需更改代码中的引脚号。你可以在这里阅读更多关于使用软件 SPI 和MCP3008 的详细信息，https://learn.adafruit.com/raspberry-pi-analog-to-digital-converters/mcp3008#software-spi

GPIO 图像供将来参考，