扩大这个问题。我正在研究几种将HD44780连接到GPIO引脚的方法以及各种折衷方案。
到目前为止，我只使用了6个GPIO引脚即可工作，类似于Adafruit上的教程，而I²C版本则使用MCP23017。
我想开始工作的其他想法是：
在6 GPIO引脚版本很简单，但使用6有价值的GPIO引脚
的CD4094的版本是很便宜，只需要2个GPIO引脚
的I²C版本仅稍贵，但可以用一个单一的MCP23017运行最多6个显示器和共享I²C与其他设备
谁能想到其他选择尝试？
Answers:
这是我当前正在使用的代码。到目前为止，只有GPIO可以正常工作。查看该test_gpio功能以查看/更改哪些GPIO引脚连接到LCD模块上的哪些引脚。
import time
import RPi.GPIO as GPIO
class LCD_GPIO(object):
# Timing constants
E_PULSE = 0.00005
E_DELAY = 0.00005
def __init__(self, RS, E, D4, D5, D6, D7):
self.RS = RS
self.E = E
self.D4 = D4
self.D5 = D5
self.D6 = D6
self.D7 = D7
GPIO.setmode(GPIO.BCM) # Use BCM GPIO numbers
GPIO.setup(self.E, GPIO.OUT) # E
GPIO.setup(self.RS, GPIO.OUT) # RS
GPIO.setup(self.D4, GPIO.OUT) # DB4
GPIO.setup(self.D5, GPIO.OUT) # DB5
GPIO.setup(self.D6, GPIO.OUT) # DB6
GPIO.setup(self.D7, GPIO.OUT) # DB7
def lcd_byte(self, data, mode):
GPIO.output(self.RS, mode)
for bits in (data>>4, data):
GPIO.output(self.D4, bits&0x01)
GPIO.output(self.D5, bits&0x02)
GPIO.output(self.D6, bits&0x04)
GPIO.output(self.D7, bits&0x08)
# Toggle E
time.sleep(self.E_DELAY)
GPIO.output(self.E, True)
time.sleep(self.E_PULSE)
GPIO.output(self.E, False)
time.sleep(self.E_DELAY)
class LCD_23017(object):
pass
class LCD_4094(object):
pass
class HD47780(object):
LCD_CHR = True
LCD_CMD = False
# Base addresses for lines on a 20x4 display
LCD_BASE = 0x80, 0xC0, 0x94, 0xD4
def __init__(self, driver, rows=2, width=16):
self.rows = rows
self.width = width
self.driver = driver
self.lcd_init()
def lcd_init(self):
# Initialise display
lcd_byte = self.driver.lcd_byte
for i in 0x33, 0x32, 0x28, 0x0C, 0x06, 0x01:
lcd_byte(i, self.LCD_CMD)
def lcd_string(self, message):
# Send string to display
lcd_byte = self.driver.lcd_byte
lcd_byte(self.LCD_BASE[0], self.LCD_CMD)
for i in bytearray(message.ljust(self.width)):
lcd_byte(i, self.LCD_CHR)
def test_gpio():
driver = LCD_GPIO(RS=7, E=8, D4=25, D5=24, D6=23, D7=18)
lcd = HD47780(driver=driver, rows=4, width=20)
lcd.lcd_string("Welcome gnibbler")
def main():
test_gpio()
if __name__ == "__main__":
main()
连接起来非常简单。我正在使用的特定显示器的对比针（V O）需要接地。通常，您将其连接到电位计以设置V SS和V CC之间的电压
我的显示器没有背光，因此我没有连接显示器以减少原理图上的混乱。如果您有背光，您当然应该以通常的方式连接它
您最多可以将3个显示器并联连接到MCP23017的每个端口。唯一的区别是每个显示器需要将使能引脚连接到单独的引脚（GPB1-GPB3）
#!/usr/bin/env python
"""World Clock Demo
It should be fairly obvious how to change this code to work for other timezones"""
import time
class LCD_23017(object):
# Timing constants
E_PULSE = 0.00005
E_DELAY = 0.00005
def __init__(self, bus, addr, port, rs, en):
self.bus = bus
self.addr = addr
self.rs = rs
self.en = en
self.DIRECTION = 0x00 if port == 'A' else 0x01
self.DATA = 0x12 if port == 'A' else 0x13
self.bus.write_byte_data(addr, self.DIRECTION, 0x00)
def lcd_byte(self, data, rs):
rs <<= self.rs
en = 1 << self.en
for nybble in (data&0xf0, data<<4):
self.bus.write_byte_data(self.addr, self.DATA, nybble | rs)
time.sleep(self.E_DELAY)
self.bus.write_byte_data(self.addr, self.DATA, nybble | rs | en)
time.sleep(self.E_PULSE)
self.bus.write_byte_data(self.addr, self.DATA, nybble | rs)
class HD47780(object):
LCD_CHR = True
LCD_CMD = False
# Base addresses for lines on a 20x4 display
LCD_BASE = 0x80, 0xC0, 0x94, 0xD4
def __init__(self, driver, rows=2, width=16):
self.rows = rows
self.width = width
self.driver = driver
self.lcd_init()
def lcd_init(self):
# Initialise display
lcd_byte = self.driver.lcd_byte
for i in 0x33, 0x32, 0x28, 0x0C, 0x06, 0x01:
lcd_byte(i, self.LCD_CMD)
def lcd_string(self, message, line=0):
# Send string to display
lcd_byte = self.driver.lcd_byte
lcd_byte(self.LCD_BASE[line], self.LCD_CMD)
for i in bytearray(message.ljust(self.width)):
lcd_byte(i, self.LCD_CHR)
def test_i2c():
from datetime import datetime
import pytz
import smbus
## For Rev1.0 Raspberry Pi
driver1 = LCD_23017(bus=smbus.SMBus(0), addr=0x27, port='B', rs=0, en=1)
driver2 = LCD_23017(bus=smbus.SMBus(0), addr=0x27, port='B', rs=0, en=2)
driver3 = LCD_23017(bus=smbus.SMBus(0), addr=0x27, port='B', rs=0, en=3)
## For Rev2.0 Raspberry Pi
#driver1 = LCD_23017(bus=smbus.SMBus(1), addr=0x27, port='B', rs=0, en=1)
#driver2 = LCD_23017(bus=smbus.SMBus(1), addr=0x27, port='B', rs=0, en=2)
#driver3 = LCD_23017(bus=smbus.SMBus(1), addr=0x27, port='B', rs=0, en=3)
lcd1 = HD47780(driver=driver1, rows=2, width=16)
lcd2 = HD47780(driver=driver2, rows=2, width=16)
lcd3 = HD47780(driver=driver3, rows=2, width=16)
lcd1.lcd_string(" New York")
lcd2.lcd_string(" London")
lcd3.lcd_string(" Melbourne")
new_york_tz = pytz.timezone("America/New_York")
london_tz = pytz.timezone("Europe/London")
melbourne_tz = pytz.timezone("Australia/Melbourne")
while True:
time.sleep(1-time.time()%1) # Wait until the next second
lcd1.lcd_string(datetime.now(new_york_tz).ctime()[3:], line=1)
lcd2.lcd_string(datetime.now(london_tz).ctime()[3:], line=1)
lcd3.lcd_string(datetime.now(melbourne_tz).ctime()[3:], line=1)
def main():
test_i2c()
if __name__ == "__main__":
main()