LCD1602多引脚面对Raspberry Pi 引脚有限的解决方法

晶晶-353740 · 发表于 2016-2-26 08:50:20

LCD1602多引脚面对Raspberry Pi 引脚有限的情况，就显得由为重要。

先来来Python 的实现方法，主要是利用python-smbus
方案方法
sudo apt-get install python-smbus
sudo apt-get install i2c-tools

MCP8574 的代码如下Qtgz_PCF8574.py

from Qtgz_I2C import Qtgz_I2C
import smbus
import time
class Qtgz_MCP8574(object):
OUTPUT = 0
INPUT = 1
def __init__(self, address, num_gpios, busnum=-1):
assert num_gpios >= 0 and num_gpios <= 8, "Number of GPIOs must be between 0 and 16"
self.i2c = Qtgz_I2C(address=address, busnum=busnum)
self.address = address
self.num_gpios = num_gpios
def _changebit(self, bitmap, bit, value):
assert value == 1 or value == 0, "Value is %s must be 1 or 0" % value
if value == 0:
return bitmap & ~(1 << bit)
elif value == 1:
return bitmap | (1 << bit)
def _readandchangepin(self, pin, value, currvalue = None):
assert pin >= 0 and pin < self.num_gpios, &quotin number %s is invalid, only 0-%s are valid" % (pin, self.num_gpios)
#assert self.direction & (1 << pin) == 0, &quotin %s not set to output" % pin
if not currvalue:
currvalue = self.i2c.readRaw8()
newvalue = self._changebit(currvalue, pin, value)
self.i2c.writeRaw8(newvalue)
return newvalue
def config(self, pin, mode):
if self.num_gpios <= 8:
self.direction = self._readandchangepin(pin, mode)
return self.direction
def output(self, pin, value):
if self.num_gpios <= 8:
self.outputvalue = self._readandchangepin(pin, value, self.i2c.readRaw8())
return self.outputvalue
def input(self, pin):
assert pin >= 0 and pin < self.num_gpios, &quotin number %s is invalid, only 0-%s are valid" % (pin, self.num_gpios)
assert self.direction & (1 << pin) != 0, &quotin %s not set to input" % pin
if self.num_gpios <= 8:
value = self.i2c.readRaw8()
return value & (1 << pin)
def readU8(self):
result = self.i2c.readRaw8()
return(result)
def readS8(self):
result = self.i2c.readRaw8()
if (result > 127): result -= 256
return result
def write8(self, value):
self.i2c.writeRaw8(value)
class PCF8574_GPIO(object):
OUT = 0
IN = 1
BCM = 0
BOARD = 0
def __init__(self, busnum, address, num_gpios):
self.chip = Qtgz_MCP8574(address, num_gpios, busnum)
def setmode(self, mode):
# do nothing
pass
def setup(self, pin, mode):
self.chip.config(pin, mode)
def input(self, pin):
return self.chip.input(pin)
def output(self, pin, value):
self.chip.output(pin, value)
if __name__ == '__main__':
# ***************************************************
# Set num_gpios to 8 for MCP8574
# ***************************************************
mcp = Qtgz_MCP8574(address = 0x27, num_gpios = 8) # MCP8574
mcp.config(3, mcp.OUTPUT)
# Set pin 3 to input with the pullup resistor enabled
#mcp.config(3, mcp.INPUT)
# Read input pin and display the results
#print &quotin 3 = %d" % (mcp.input(3) >> 3)
# Python speed test on output 3 toggling at max speed
print "Starting blinky on pin 3 (CTRL+C to quit)"
while (True):
mcp.output(3, 1) # Pin 0 High
time.sleep(1);
mcp.output(3, 0) # Pin 0 Low
time.sleep(1);

复制代码
LCD1602 的代码

from time import sleep
class Adafruit_CharLCD(object):
# 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=25, pin_e=24, pins_db=[23, 17, 21, 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
GPIO.setwarnings(False)
self.GPIO = GPIO
self.pin_rs = pin_rs
self.pin_e = pin_e
self.pins_db = pins_db
self.GPIO.setmode(GPIO.BCM) #GPIO=None use Raspi PIN in BCM mode
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
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 off """
self.displaycontrol &= ~self.LCD_CURSORON
self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
def cursor(self):
""" Turns the underline cursor on """
self.displaycontrol |= self.LCD_CURSORON
self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
def noBlink(self):
""" Turn the blinking cursor off """
self.displaycontrol &= ~self.LCD_BLINKON
self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
def blink(self):
""" Turn the blinking cursor on """
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 == "1":
self.GPIO.output(self.pins_db[::-1], True)
self.pulseEnable()
for pin in self.pins_db:
self.GPIO.output(pin, False)
for i in range(4, 8):
if bits == "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(" Adafruit 16x2\n Standard LCD")

复制代码
实现代码如下，打印内部温度，内存使用情况

#!/usr/bin/python

# -*- coding: utf-8 -*-

from Adafruit_CharLCD import Adafruit_CharLCD

from Qtgz_PCF8574 import PCF8574_GPIO

from subprocess import *

from time import sleep, strftime

from datetime import datetime

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'

bus = 1    # Note you need to change the bus number to 0 if running on a revision 1 Raspberry Pi.

address = 0x27 # I2C address of the PCF8574 chip.

gpio_count = 8 # Number of GPIOs exposed by the PCF8574 chip, should be 8 or 16 depending on chip.

# Create PCF8574 GPIO adapter.

mcp = PCF8574_GPIO(bus, address, gpio_count)

# Create LCD, passing in MCP GPIO adapter.

lcd = Adafruit_CharLCD(pin_rs=0, pin_e=2, pins_db=[4,5,6,7], GPIO=mcp)

if __name__ == '__main__':

while(1):

   lcd.clear()

   lcd.message( get_ip_info() )

   sleep(1)

   lcd.clear()

   lcd.message( get_time_now() )

   sleep(1)

   lcd.clear()

   lcd.message( get_mem_info() )

   sleep(1)

   lcd.clear()

   lcd.message( 'CPU: ' + get_cpu_temp()+'\n' )

   lcd.message( 'GPU: ' + get_gpu_temp() )

   sleep(1)

复制代码
效果如下

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