lcd_i2c_class.py

#!/usr/bin/env python
#
# LCD test program for the lcd_i2c_class.py class
# $Id: lcd_i2c_class.py,v 1.2 2014/10/05 08:38:31 bob Exp $
# Use this program to test I2C Backpack LCD wiring
# Adapted from RpiLcdBackpack from Paul Knox-Kennedy
# at Adafruit Industries
#
# Author : Bob Rathbone
# Site	 : http://www.bobrathbone.com
#
# License: GNU V3, See https://www.gnu.org/copyleft/gpl.html
#
# Disclaimer: Software is provided as is and absolutly no warranties are implied or given.
#						 The authors shall not be liable for any loss or damage however caused.
#

import smbus,time
from subprocess import * 
from time import sleep, strftime
from datetime import datetime

class lcd_i2c:
	# commands
	__CLEARDISPLAY=0x01
	__RETURNHOME=0x02
	__ENTRYMODESET=0x04
	__DISPLAYCONTROL=0x08
	__CURSORSHIFT=0x10
	__FUNCTIONSET=0x20
	__SETCGRAMADDR=0x40
	__SETDDRAMADDR=0x80

	# flags for display entry mode
	__ENTRYRIGHT=0x00
	__ENTRYLEFT=0x02
	__ENTRYSHIFTINCREMENT=0x01
	__ENTRYSHIFTDECREMENT=0x00

	# flags for display on/off control
	__DISPLAYON=0x04
	__DISPLAYOFF=0x00
	__CURSORON=0x02
	__CURSOROFF=0x00
	__BLINKON=0x01
	__BLINKOFF=0x00

	# flags for display/cursor shift
	__DISPLAYMOVE=0x08
	__CURSORMOVE=0x00
	__MOVERIGHT=0x04
	__MOVELEFT=0x00

	# flags for function set
	__8BITMODE=0x10
	__4BITMODE=0x00
	__2LINE=0x08
	__1LINE=0x00
	__5x10DOTS=0x04
	__5x8DOTS=0x00

	_rs=0x02
	_e=0x4
	_dataMask=0x78
	_dataShift=3
	_light=0x80

	# Define LCD device constants
	LCD_WIDTH = 16    # Default 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

	width = LCD_WIDTH
	ScrollSpeed = 0.3       # Default scroll speed

	# Write nibble to LCD position 
	def writeFourBits(self,value):
		self.__data &= ~self._dataMask
		self.__data |= value << self._dataShift
		self.__data &= ~self._e 
		self.__bus.write_byte_data(0x20,0x09,self.__data)
		time.sleep(0.000001)
		self.__data |= self._e 
		self.__bus.write_byte_data(0x20,0x09,self.__data)
		time.sleep(0.000001)
		self.__data &= ~self._e 
		self.__bus.write_byte_data(0x20,0x09,self.__data)
		time.sleep(0.000101)

	def writeCommand(self,value):
		self.__data &= ~self._rs
		self.writeFourBits(value>>4)
		self.writeFourBits(value&0xf)

	def writeData(self,value):
		self.__data |= self._rs
		self.writeFourBits(value>>4)
		self.writeFourBits(value&0xf)

	# Do nothing on init
	def __init__(self):
		return

	# Initialisation routine
	def init(self, board_rev=2):
		bus=1
		if board_rev == 1:
			bus = 0
		
		self.__bus=smbus.SMBus(bus)
		self.__bus.write_byte_data(0x20,0x00,0x00)
		self.__displayfunction = self.__4BITMODE | self.__2LINE | self.__5x8DOTS
		self.__displaycontrol = self.__DISPLAYCONTROL | self.__DISPLAYON | self.__CURSORON | self.__BLINKON
		self.__data = 0
		self.writeFourBits(0x03)
		time.sleep(0.005)
		self.writeFourBits(0x03)
		time.sleep(0.00015)
		self.writeFourBits(0x03)
		self.writeFourBits(0x02)
		self.writeCommand(self.__FUNCTIONSET | self.__displayfunction)
		self.writeCommand(self.__displaycontrol)
		self.writeCommand(0x6)
		self.clear()
		self.blink(False)
		return

	# Display Line 1 on LCD
	def line1(self,text):
		self._writeLine(self.LCD_LINE_1,text)
		return

	# Display Line 2 on LCD
	def line2(self,text):
		self._writeLine(self.LCD_LINE_2,text)
		return

	# Display Line 3 on LCD
	def line3(self,text):
		self._writeLine(self.LCD_LINE_3,text)
		return

	# Display Line 4 on LCD
	def line4(self,text):
		self._writeLine(self.LCD_LINE_4,text)
		return

	# Write a single line to the LCD
	def _writeLine(self,line,text):
		self.writeCommand(line)
		if len(text) < self.width:
			text = text.ljust(self.width, ' ')
		self.message(text[:self.width])
		return

	# Scroll message on line 1
	def scroll1(self,mytext,interrupt):
		self._scroll(mytext,self.LCD_LINE_1,interrupt)
		return

	# Scroll message on line 2
	def scroll2(self,mytext,interrupt):
		self._scroll(mytext,self.LCD_LINE_2,interrupt)
		return

	# Scroll message on line 3
	def scroll3(self,mytext,interrupt):
		self._scroll(mytext,self.LCD_LINE_3,interrupt)
		return

	# Scroll message on line 4
	def scroll4(self,mytext,interrupt):
		self._scroll(mytext,self.LCD_LINE_4,interrupt)
		return


	# Scroll line - interrupt() breaks out routine if True
	def _scroll(self,mytext,line,interrupt):
		ilen = len(mytext)
		skip = False

		self._writeLine(line,mytext[0:self.width + 1])

		if (ilen <= self.width):
			skip = True

		if not skip:
			for i in range(0, 5):
				time.sleep(0.2)
				if interrupt():
					skip = True
					break

		if not skip:
			for i in range(0, ilen - self.width + 1 ):
				self._writeLine(line,mytext[i:i+self.width])
				if interrupt():
					skip = True
					break
				time.sleep(self.ScrollSpeed)

		if not skip:
			for i in range(0, 5):
				time.sleep(0.2)
				if interrupt():
					break
		return



	# Switch back light on and off
	def backlight(self,on):
		if on:
			self.__data |= 0x80
		else:
			self.__data &= 0x7f
		self.__bus.write_byte_data(0x20,0x09,self.__data)


	# Clear display
	def clear(self):
		self.writeCommand(self.__CLEARDISPLAY)
		time.sleep(0.002)


	# Blink cursor
	def blink(self, on):
		if on:
			self.__displaycontrol |= self.__BLINKON
		else:
			self.__displaycontrol &= ~self.__BLINKON
		self.writeCommand(self.__displaycontrol)

	def noCursor(self):
		self.writeCommand(self.__displaycontrol)

	def cursor(self, on):
		if on:
			self.__displaycontrol |= self.__CURSORON
		else:
			self.__displaycontrol &= ~self.__CURSORON
		self.writeCommand(self.__displaycontrol)

	def message(self, text):
		for char in text:
			if char == '\n':
				self.writeCommand(0xC0)
			else:
				self.writeData(ord(char))

	# Set the display width
	def setWidth(self,width):
		self.width = width
		return

	# Set Scroll line speed - Best values are 0.2 and 0.3
	# Limit to between 0.05 and 1.0
	def setScrollSpeed(self,speed):
		if speed < 0.05:
			speed = 0.2
		elif speed > 1.0:
			speed = 0.3
		self.ScrollSpeed = speed
		return

# End of lcd_i2c_class