I2C display for RPI 2 (model B+)

main.py

# -*- coding: utf-8 -*-
# original soruce: https://terutakke.com/diary/1602-i2c-serial-lcd-modul/

from time import sleep
from time import gmtime, strftime

import RPi.GPIO as GPIO
import datetime
import smbus

# I/F https://github.com/szazo/DHT11_Python
import dht11


#initialize GPIO
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.cleanup()

#read data using pin4
instance = dht11.DHT11(pin=4)


# Define some device parameters
I2C_ADDR  = 0x3f # I2C device address #アドレスが違う場合もあるかもしれない
LCD_WIDTH = 16   # Maximum characters per line

# Define some device constants
LCD_CHR = 1 # Mode - Sending data
LCD_CMD = 0 # Mode - Sending command

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line

LCD_BACKLIGHT  = 0x08  # On
# LCD_BACKLIGHT = 0x00  # Off

ENABLE = 0b00000100 # Enable bit

# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005

#Open I2C interface
# bus = smbus.SMBus(0)  # Rev 1 Pi uses 0
bus = smbus.SMBus(1) # Rev 2 Pi uses 1

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
  sleep(E_DELAY)

def lcd_byte(bits, mode):
  # Send byte to data pins
  # bits = the data
  # mode = 1 for data
  #        0 for command
  bits_high = mode | (bits & 0xF0) | LCD_BACKLIGHT
  bits_low = mode | ((bits<<4) & 0xF0) | LCD_BACKLIGHT

  # High bits
  bus.write_byte(I2C_ADDR, bits_high)
  lcd_toggle_enable(bits_high)

  # Low bits
  bus.write_byte(I2C_ADDR, bits_low)
  lcd_toggle_enable(bits_low)

def lcd_toggle_enable(bits):
  # Toggle enable
  sleep(E_DELAY)
  bus.write_byte(I2C_ADDR,(bits | ENABLE))
  sleep(E_PULSE)
  bus.write_byte(I2C_ADDR,(bits & ~ENABLE))
  sleep(E_DELAY)
  

def lcd_string(message,line):
  # Send string to display
  message = message.ljust(LCD_WIDTH," ")
  lcd_byte(line, LCD_CMD)
  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)

def main(): #「日時」を表示
    # Main program block
    # Initialise display
    lcd_init()
    while True:
      local_time = datetime.datetime.now()
      str1 = strftime("%Y.%m.%d (%a)", gmtime())
      str2 = local_time.strftime("%H:%M")
      lcd_string(str1, LCD_LINE_1)
      lcd_string(str2, LCD_LINE_2)
      sleep(1)

      local_time = datetime.datetime.now()
      lcd_string(strftime("%Y.%m.%d (%a)", gmtime()) , LCD_LINE_1)
      lcd_string(local_time.strftime("%H %M"), LCD_LINE_2)
      sleep(1)

try:        
  print('Start:' + str(datetime.datetime.now()))
  main()
except KeyboardInterrupt:
  pass
finally:
  LCD_BACKLIGHT = 0x00  #バックライトオフ
  lcd_byte(0x01, LCD_CMD) #表示内容クリア
  GPIO.cleanup()