20 x 4 Line 2 scrolling text for LCD-I2C Display

[RoadieMunky]

Hello Everyone,
I am new to coding and the Raspberry Pi, and I hope you can help me out?
I have a code to display to an LCD-I2C 20x4 display but I want (LCD_LINE_2) to scroll from Right to Left. This would be easy if I had just 1 line of the same text to display, but for each #Train I want a different set of "Calling At" stations so the text will change every time.
I have tried contacting the person who wrote he code but I have had no reply.
I am using Python3.x
Thank you for any and all help in this matter.

#!/usr/bin/python
#--------------------------------------
#    ___  ___  _ ____
#   / _ \/ _ \(_) __/__  __ __
#  / , _/ ___/ /\ \/ _ \/ // /
# /_/|_/_/  /_/___/ .__/\_, /
#                /_/   /___/
#
#  lcd_i2c.py
#  LCD test script using I2C backpack.
#  Supports 16x2 and 20x4 screens.
#
# Author : Matt Hawkins
# Date   : 20/09/2015
#
# http://www.raspberrypi-spy.co.uk/
#
# Copyright 2015 Matt Hawkins
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#--------------------------------------
import smbus
import time

# Define some device parameters
I2C_ADDR  = 0x27 # I2C device address
LCD_WIDTH = 20   # 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_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 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 = 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
  time.sleep(E_DELAY)
  bus.write_byte(I2C_ADDR, (bits | ENABLE))
  time.sleep(E_PULSE)
  bus.write_byte(I2C_ADDR,(bits & ~ENABLE))
  time.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():
  # Main program block

  # Initialise display
  lcd_init()

  while True:
    
    # Train 1
    lcd_string("1st Victoria Only",LCD_LINE_1)
    lcd_string("Calling At Victoria Only",LCD_LINE_2)
    lcd_string("2nd Orpington",LCD_LINE_3)
    lcd_string("3rd Wisbech         ",LCD_LINE_4)

    time.sleep(180)
  
    # Train 2
    lcd_string("1st Orpington",LCD_LINE_1)
    lcd_string("Calling At Bromley, Petts Wood, Bickley And Orpington",LCD_LINE_2)
    lcd_string("2nd Wisbech",LCD_LINE_3)
    lcd_string("3rd Victoria",LCD_LINE_4)

    time.sleep(180)
    
    # Train 3
    lcd_string("1st Wisbech",LCD_LINE_1)
    lcd_string("Calling At Peterborough, Ely and Wisbech",LCD_LINE_2)
    lcd_string("2nd Victoria",LCD_LINE_3)
    lcd_string("3rd Orpington",LCD_LINE_4)
    
    time.sleep(180)
    

if __name__ == '__main__':

  try:
    main()
  except KeyboardInterrupt:
    pass
  finally:
    lcd_byte(0x01, LCD_CMD)

[marsokod]

How do you expect to get the text you want to display? Is it written in a file, or do want to generate automatically in your code?

[RoadieMunky]

Hi Marsokod,
The text is in the code at the bottom, under the "While True". it does display on the LCD, but as "LCD_LINE_2" is longer than the 20 characters, I need that line to scroll, which it does not do currently. I have found scrolling strings, but I can only put one line of text in (e.g. "this is my long string"). In my case I need the text to change for each #Train as they have different "Calling at" stations.

This project is for a model railway, but i want it to mimic a real life train station display board, but I won't be using real train station names when I'm finished.

I hope this helps, any other questions please don't hesitate to ask.
Thanks,
RoadieMunky