temperature (DHT11) with LCD (via i2c)

# Drive 16x2 LCD with i2c LCD

import smbus

import time

# get drives for dht11

import dht11

import RPi.GPIO as GPIO

# define device parameters

I2C_ADDR = 0x27 #address for GPIO pin to LCD

LCD_WIDTH = 16 #Max characters per line

# define GPIO to LCD mapping

Temp_sensor = 14

# 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_LINE_3 = 0x94 # LCD RAM address for the 3rd line

LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th 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 main():

  # Main program block

  GPIO.setwarnings(False)

  GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers

  instance = dht11.DHT11(pin = Temp_sensor)

  # Initialise display

  lcd_init()

  while True:

        #get DHT11 sensor value

        result = instance.read()

    # Send some test

        if result.is_valid():

                lcd_string("temp:"+str(result.temperature)+" C",LCD_LINE_1)

                lcd_string("humid:"+str(result.humidity)+"%",LCD_LINE_2)

                time.sleep(3) # 3 second delay

                lcd_string("wohooo ",LCD_LINE_1)

                lcd_string("now to get it online",LCD_LINE_2)

                time.sleep(3)

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

  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)

  # Toggle 'Enable' pin

 # lcd_toggle_enable()

def lcd_toggle_enable(bits):

  # Toggle enable

  time.sleep(E_DELAY)

  bus.write_byte(I2C_ADDR, (bits | ENABLE))

  time.sleep(E_PULSE)

  bus.write_byte(I2C_ADDR,(bits & ~ENABLE))

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)

if __name__ == '__main__':

  try:

    main()

  except KeyboardInterrupt:

    pass

  finally:

    lcd_byte(0x01, LCD_CMD)

    lcd_string("Goodbye!",LCD_LINE_1)

    GPIO.cleanup()