RaspberryPi I2C LCD Python stuff

examples.py

# requires RPi_I2C_driver.py
import RPi_I2C_driver
from time import *

mylcd = RPi_I2C_driver.lcd()
# test 2
mylcd.lcd_display_string("RPi I2C test", 1)
mylcd.lcd_display_string(" Custom chars", 2)

sleep(2) # 2 sec delay

mylcd.lcd_clear()

# let's define a custom icon, consisting of 6 individual characters
# 3 chars in the first row and 3 chars in the second row
fontdata1 = [
        # Char 0 - Upper-left
        [ 0x00, 0x00, 0x03, 0x04, 0x08, 0x19, 0x11, 0x10 ],
        # Char 1 - Upper-middle
        [ 0x00, 0x1F, 0x00, 0x00, 0x00, 0x11, 0x11, 0x00 ],
        # Char 2 - Upper-right
        [ 0x00, 0x00, 0x18, 0x04, 0x02, 0x13, 0x11, 0x01 ],
        # Char 3 - Lower-left
        [ 0x12, 0x13, 0x1b, 0x09, 0x04, 0x03, 0x00, 0x00 ],
        # Char 4 - Lower-middle
        [ 0x00, 0x11, 0x1f, 0x1f, 0x0e, 0x00, 0x1F, 0x00 ],
        # Char 5 - Lower-right
        [ 0x09, 0x19, 0x1b, 0x12, 0x04, 0x18, 0x00, 0x00 ],
        # Char 6 - my test
	[ 0x1f,0x0,0x4,0xe,0x0,0x1f,0x1f,0x1f],
]

# Load logo chars (fontdata1)
mylcd.lcd_load_custom_chars(fontdata1)


# Write first three chars to row 1 directly
mylcd.lcd_write(0x80)
mylcd.lcd_write_char(0)
mylcd.lcd_write_char(1)
mylcd.lcd_write_char(2)
# Write next three chars to row 2 directly
mylcd.lcd_write(0xC0)
mylcd.lcd_write_char(3)
mylcd.lcd_write_char(4)
mylcd.lcd_write_char(5)
sleep(2)

mylcd.lcd_clear()

mylcd.lcd_display_string_pos("Testing",1,1) # row 1, column 1
sleep(1)
mylcd.lcd_display_string_pos("Testing",2,3) # row 2, column 3
sleep(1)
mylcd.lcd_clear()

# Now let's define some more custom characters
fontdata2 = [
        # Char 0 - left arrow
        [ 0x1,0x3,0x7,0xf,0xf,0x7,0x3,0x1 ],
        # Char 1 - left one bar 
        [ 0x10,0x10,0x10,0x10,0x10,0x10,0x10,0x10 ],
        # Char 2 - left two bars
        [ 0x18,0x18,0x18,0x18,0x18,0x18,0x18,0x18 ],
        # Char 3 - left 3 bars
        [ 0x1c,0x1c,0x1c,0x1c,0x1c,0x1c,0x1c,0x1c ],
        # Char 4 - left 4 bars
        [ 0x1e,0x1e,0x1e,0x1e,0x1e,0x1e,0x1e,0x1e ],
        # Char 5 - left start
        [ 0x0,0x1,0x3,0x7,0xf,0x1f,0x1f,0x1f ],
        # Char 6 - 
        # [ ],
]

# Load logo chars from the second set
mylcd.lcd_load_custom_chars(fontdata2)

block = chr(255) # block character, built-in

# display two blocks in columns 5 and 6 (i.e. AFTER pos. 4) in row 1
# first draw two blocks on 5th column (cols 5 and 6), starts from 0
mylcd.lcd_display_string_pos(block * 2,1,4)

# 
pauza = 0.2 # define duration of sleep(x)
#
# now draw cust. chars starting from col. 7 (pos. 6)

pos = 6
mylcd.lcd_display_string_pos(unichr(1),1,6)
sleep(pauza)

mylcd.lcd_display_string_pos(unichr(2),1,pos)
sleep(pauza)

mylcd.lcd_display_string_pos(unichr(3),1,pos)
sleep(pauza)

mylcd.lcd_display_string_pos(unichr(4),1,pos)
sleep(pauza)

mylcd.lcd_display_string_pos(block,1,pos)
sleep(pauza)

# and another one, same as above, 1 char-space to the right
pos = pos +1 # increase column by one

mylcd.lcd_display_string_pos(unichr(1),1,pos)
sleep(pauza)
mylcd.lcd_display_string_pos(unichr(2),1,pos)
sleep(pauza)
mylcd.lcd_display_string_pos(unichr(3),1,pos)
sleep(pauza)
mylcd.lcd_display_string_pos(unichr(4),1,pos)
sleep(pauza)
mylcd.lcd_display_string_pos(block,1,pos)
sleep(pauza)


#
# now again load first set of custom chars - smiley
mylcd.lcd_load_custom_chars(fontdata1)

mylcd.lcd_display_string_pos(unichr(0),1,9)
mylcd.lcd_display_string_pos(unichr(1),1,10)
mylcd.lcd_display_string_pos(unichr(2),1,11)
mylcd.lcd_display_string_pos(unichr(3),2,9)
mylcd.lcd_display_string_pos(unichr(4),2,10)
mylcd.lcd_display_string_pos(unichr(5),2,11)

sleep(2)
mylcd.lcd_clear()
sleep(1)
mylcd.backlight(0)

RPi_I2C_driver.py

# -*- coding: utf-8 -*-
"""
Compiled, mashed and generally mutilated 2014-2015 by Denis Pleic
Made available under GNU GENERAL PUBLIC LICENSE

# Modified Python I2C library for Raspberry Pi
# as found on http://www.recantha.co.uk/blog/?p=4849
# Joined existing 'i2c_lib.py' and 'lcddriver.py' into a single library
# added bits and pieces from various sources
# By DenisFromHR (Denis Pleic)
# 2015-02-10, ver 0.1

"""
#
#
import smbus
from time import *

class i2c_device:
   def __init__(self, addr, port=1):
      self.addr = addr
      self.bus = smbus.SMBus(port)

# Write a single command
   def write_cmd(self, cmd):
      self.bus.write_byte(self.addr, cmd)
      sleep(0.0001)

# Write a command and argument
   def write_cmd_arg(self, cmd, data):
      self.bus.write_byte_data(self.addr, cmd, data)
      sleep(0.0001)

# Write a block of data
   def write_block_data(self, cmd, data):
      self.bus.write_block_data(self.addr, cmd, data)
      sleep(0.0001)

# Read a single byte
   def read(self):
      return self.bus.read_byte(self.addr)

# Read
   def read_data(self, cmd):
      return self.bus.read_byte_data(self.addr, cmd)

# Read a block of data
   def read_block_data(self, cmd):
      return self.bus.read_block_data(self.addr, cmd)



# LCD Address
ADDRESS = 0x27

# 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
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

# flags for backlight control
LCD_BACKLIGHT = 0x08
LCD_NOBACKLIGHT = 0x00

En = 0b00000100 # Enable bit
Rw = 0b00000010 # Read/Write bit
Rs = 0b00000001 # Register select bit

class lcd:
   #initializes objects and lcd
   def __init__(self):
      self.lcd_device = i2c_device(ADDRESS)

      self.lcd_write(0x03)
      self.lcd_write(0x03)
      self.lcd_write(0x03)
      self.lcd_write(0x02)

      self.lcd_write(LCD_FUNCTIONSET | LCD_2LINE | LCD_5x8DOTS | LCD_4BITMODE)
      self.lcd_write(LCD_DISPLAYCONTROL | LCD_DISPLAYON)
      self.lcd_write(LCD_CLEARDISPLAY)
      self.lcd_write(LCD_ENTRYMODESET | LCD_ENTRYLEFT)
      sleep(0.2)


   # clocks EN to latch command
   def lcd_strobe(self, data):
      self.lcd_device.write_cmd(data | En | LCD_BACKLIGHT)
      sleep(.0005)
      self.lcd_device.write_cmd(((data & ~En) | LCD_BACKLIGHT))
      sleep(.0001)

   def lcd_write_four_bits(self, data):
      self.lcd_device.write_cmd(data | LCD_BACKLIGHT)
      self.lcd_strobe(data)

   # write a command to lcd
   def lcd_write(self, cmd, mode=0):
      self.lcd_write_four_bits(mode | (cmd & 0xF0))
      self.lcd_write_four_bits(mode | ((cmd << 4) & 0xF0))

   # write a character to lcd (or character rom) 0x09: backlight | RS=DR<
   # works!
   def lcd_write_char(self, charvalue, mode=1):
      self.lcd_write_four_bits(mode | (charvalue & 0xF0))
      self.lcd_write_four_bits(mode | ((charvalue << 4) & 0xF0))
  

   # put string function
   def lcd_display_string(self, string, line):
      if line == 1:
         self.lcd_write(0x80)
      if line == 2:
         self.lcd_write(0xC0)
      if line == 3:
         self.lcd_write(0x94)
      if line == 4:
         self.lcd_write(0xD4)

      for char in string:
         self.lcd_write(ord(char), Rs)

   # clear lcd and set to home
   def lcd_clear(self):
      self.lcd_write(LCD_CLEARDISPLAY)
      self.lcd_write(LCD_RETURNHOME)

   # define backlight on/off (lcd.backlight(1); off= lcd.backlight(0)
   def backlight(self, state): # for state, 1 = on, 0 = off
      if state == 1:
         self.lcd_device.write_cmd(LCD_BACKLIGHT)
      elif state == 0:
         self.lcd_device.write_cmd(LCD_NOBACKLIGHT)

   # add custom characters (0 - 7)
   def lcd_load_custom_chars(self, fontdata):
      self.lcd_write(0x40);
      for char in fontdata:
         for line in char:
            self.lcd_write_char(line)         
         
   # define precise positioning (addition from the forum)
   def lcd_display_string_pos(self, string, line, pos):
    if line == 1:
      pos_new = pos
    elif line == 2:
      pos_new = 0x40 + pos
    elif line == 3:
      pos_new = 0x14 + pos
    elif line == 4:
      pos_new = 0x54 + pos

    self.lcd_write(0x80 + pos_new)

    for char in string:
      self.lcd_write(ord(char), Rs)

Thanks for the code Dennis. Here's what I'm using for text scrolling in case it helps anyone:

async def display(lcd, display_queue):
    ln1, ln2 = "", ""
    ln1_i, ln2_i = 0, 0
    while True:
        if not display_queue.empty():
            ln1, ln2 = await display_queue.get()
            ln1_i, ln2_i = 0, 0
            lcd.lcd_clear()
        else:
            ln1_i = 0 if len(ln1) <= 16 else (ln1_i + 1) % (len(ln1) - NUM_COLS + 1)
            ln2_i = 0 if len(ln2) <= 16 else (ln2_i + 1) % (len(ln2) - NUM_COLS + 1)

        lcd.lcd_display_string(ln1[ln1_i:ln1_i+NUM_COLS], 1)
        lcd.lcd_display_string(ln2[ln2_i:ln2_i+NUM_COLS], 2)

        await asyncio.sleep(0.5)

where display_queue is an asyncio.Queue.
To display something, call await display_queue.put(("Loooooooooooooooooonng", "Teeeeeeeeeeeeeeeeeeext"))

Hi Dennis,

Thank you for your work on this. I attempted to make this work in the 8-bit mode but have not been able to.

116 self.lcd_write(LCD_FUNCTIONSET | LCD_2LINE | LCD_5x8DOTS | LCD_8BITMODE)

How can the following write statements be condensed into 1 line instead of the two in 8 bit mode.

def lcd_write_char(self, charvalue, mode=1):
      self.lcd_write_four_bits(mode | (charvalue & 0xF0))
      self.lcd_write_four_bits(mode | ((charvalue << 4) & 0xF0))

def lcd_write(self, cmd, mode=0):
      self.lcd_write_four_bits(mode | (cmd & 0xF0))
      self.lcd_write_four_bits(mode | ((cmd << 4) & 0xF0))

I tried this but it gives strange results even though the binary output is correct for this command:

def lcd_write(self, cmd, mode=0):
      self.lcd_write_four_bits(mode | (cmd & 0xFF))