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)

Hi, can u help me ?
When i run this file, i've this messge !

Traceback (most recent call last):
.../exampleLCD.py", line 91, in
mylcd.lcd_display_string_pos(unichr(1),1,pos)
NameError: name 'unichr' is not defined

where do i defined this 'unichr' ?
thanks

@DenisFromHR any idea what these are for?

   def __init__(self):
      self.lcd_device = i2c_device(ADDRESS)

      self.lcd_write(0x03)  # what
      self.lcd_write(0x03)  # are
      self.lcd_write(0x03)  # these
      self.lcd_write(0x02)  # for

      self.lcd_write(LCD_FUNCTIONSET | LCD_2LINE | LCD_5x8DOTS | LCD_4BITMODE)

Great stuff!

I live in Norway, but apparently I have the LCD ROM with the Japanese font set, which makes displaying the nordic characters (æ, ø, å) a real headache, at least when you're dealing with inconsistent ascii-tables and unicode (UTF8) conversions on top of that.

However, I made a custom font set with the "missing" norwegian characters, if anyone's interested.
I used this character generator, set it to "hex" datatype, and used @DenisFromHR 's example code to write the characters to the display.

Just out of curiousity:
Is there a an (relatively easy) way to "map" these custom characters to their unicode/UTF-8 counterparts?
Example: If I try to

"lcd_display_string("æøå", 1)

it would be GREAT if I somehow managed to automatically map the character "æ" to (for instance) chr(1), "ø" to chr(2) and so on.

And if everything else fails, shouldn't it be possible to do a "char.replace('ø', chr(1))", or something similar in Python? It would make the programming flow SO much easier.

Any thoughts?

Anyway, here's my (very basic) example code (updated):

import RPi_I2C_driver
lcd = RPi_I2C_driver.lcd()
fontdata1 = [
    # Æ
    [ 0x00,0x0C,0x13,0x12,0x1F,0x12,0x13,0x00 ],
    # Ø
    [ 0x01,0x0E,0x13,0x15,0x19,0x0E,0x10,0x00 ],
    # Å
    [ 0x04,0x00,0x0E,0x11,0x1F,0x11,0x11,0x00 ],
    # æ
    [ 0x00,0x00,0x1A,0x05,0x0F,0x14,0x1F,0x00 ],
    # ø
    [ 0x00,0x01,0x0E,0x15,0x15,0x0E,0x10,0x00 ],
    # å
    [ 0x04,0x00,0x0E,0x01,0x0F,0x11,0x0F,0x00 ],
    # degrees Celsius
    [ 0x08,0x14,0x0B,0x04,0x04,0x03,0x00,0x00 ],
    # humidity
    [ 0x00,0x04,0x0E,0x0E,0x1F,0x1F,0x0E,0x04 ],
    # low batt.
    [ 0x0E,0x11,0x11,0x11,0x11,0x11,0x1F,0x1F ],
    # full batt.
    [ 0x0E,0x11,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F ],
]
lcd.lcd_load_custom_chars(fontdata1)

#and to use the custom characters:
lcd.lcd_display_string(chr(2) + "some other random letters" , 1)
lcd.lcd_display_string("Batt: " + chr(9) , 2)

Update:

Here's how I managed to add the extra Norwegian characters to the font set. I know there are more efficient ways to do this, but I'm still learning Python, and for this purpose it kind of works:

lcd = RPi_I2C_driver.lcd()

LCD_NORCHARS = [
[ 0b00000,0b01111,0b10100,0b10100,0b11111,0b10100,0b10111,0b00000 ], # Æ
[ 0b00001,0b01110,0b10011,0b10101,0b10101,0b11001,0b01110,0b10000 ], # Ø
[ 0b01100,0b00000,0b01100,0b10010,0b11110,0b10010,0b10010,0b00000 ], # Å
[ 0b00000,0b00000,0b01101,0b00010,0b01111,0b10010,0b01101,0b00000 ], # æ
[ 0b00000,0b00000,0b00001,0b01110,0b10101,0b10101,0b01110,0b10000 ], # ø
[ 0b00000,0b01100,0b00000,0b01100,0b00010,0b11110,0b10010,0b01101 ], # å
]

lcd.lcd_load_custom_chars(LCD_NORCHARS)
string01 = "Æ Ø Å"
string02 = "æ ø å"

string01_N = string01.replace('Æ', chr(0)).replace('Ø', chr(1)).replace('Å', chr(2)).replace('æ', chr(3)).replace('ø', chr(4)).replace('å', chr(5)).decode('utf8')  # This would be better with a "For X in array..." loop, but I can't figure out how to do it yet
string02_N = string02.replace('Æ', chr(0)).replace('Ø', chr(1)).replace('Å', chr(2)).replace('æ', chr(3)).replace('ø', chr(4)).replace('å', chr(5)).decode('utf8')

lcd.lcd_display_string(string01_N, 1)
lcd.lcd_display_string(string02_N, 2)

Good job, Denis!
I love the user defined characters. I've created a little php script to be able to create the code for the special characters in the syntax you are using here, e.g. [ 0x0E,0x11,0x1F,0x1F,0x1F,0x1F,0x1F,0x1F ]

In case anyone is interested, here it is:
https://pastebin.com/EL1nR5MX

cheers, Martin

Hi Denis,
This looks awesome, thanks for putting this on github. I’m very interested in some examples that you mentioned in your first post to make a scrolling text.
Thanks a ton
Maikel

I'm trying to use this driver with PCF8574's younger sibling - PCA9554P with a 16x2 lcd display, but it does not work at all. I'm constantly getting a same error:

Traceback (most recent call last): File "examples.py", line 5, in <module> mylcd = RPi_I2C_driver.lcd() File "/home/pi/i2c/RPi_I2C_driver.py", line 105, in __init__ self.lcd_write(0x03) File "/home/pi/i2c/RPi_I2C_driver.py", line 130, in lcd_write self.lcd_write_four_bits(mode | (cmd & 0xF0)) File "/home/pi/i2c/RPi_I2C_driver.py", line 125, in lcd_write_four_bits self.lcd_device.write_cmd(data | LCD_BACKLIGHT) File "/home/pi/i2c/RPi_I2C_driver.py", line 24, in write_cmd self.bus.write_byte(self.addr, cmd) IOError: [Errno 121] Remote I/O error
with python 2.7.13

and

Traceback (most recent call last): File "examples.py", line 5, in <module> mylcd = RPi_I2C_driver.lcd() File "/home/pi/i2c/RPi_I2C_driver.py", line 105, in __init__ self.lcd_write(0x03) File "/home/pi/i2c/RPi_I2C_driver.py", line 130, in lcd_write self.lcd_write_four_bits(mode | (cmd & 0xF0)) File "/home/pi/i2c/RPi_I2C_driver.py", line 125, in lcd_write_four_bits self.lcd_device.write_cmd(data | LCD_BACKLIGHT) File "/home/pi/i2c/RPi_I2C_driver.py", line 24, in write_cmd self.bus.write_byte(self.addr, cmd) File "/usr/local/lib/python3.5/dist-packages/smbus/util.py", line 59, in validator return fn(*args, **kwdefaults) File "/usr/local/lib/python3.5/dist-packages/smbus/smbus.py", line 121, in write_byte raise IOError(ffi.errno) OSError: 121
with python 3.5.3

I'm using Raspbian stretch full, downloaded on 9.11.2018.
What's wrong with my situation?

Is it possible to run multiple LCD's each with a different address?

Thanks for the libs!

I've spend several hours for trying start libs working.. And I fix it with screwdriver.. Fix potentiometer brightness.

Thank you for posting this - I was pulling my hair out over the same thing.

Hi Denis
Thanks for the libs. I have two 16x2 LCD's from different shops.
It works fine on LCD 1, but LCD 2 displays sometimes a few characters, sometimes blocks, sometimes nothing, hanging for a few seconds. Switching on and off the display works. Probably a timing problem.
Any Idea where to change any delays?

Dear @DenisFromHR

Myself and some others use your code to make a contribution to the RPi-Jukebox-RFID project. This project allows to build a simple to use Jukebox like Music Player which is extremely interesting for small Kids. I use these Jukeboxes for my three Kids.
We developed a project specific script this uses directly your RPi_I2C_driver.py driver (renamed to i2c_lcd_driver.py to be compatible with the contribution regulations of the RPi-Jukebox-RFID project).

Current status is, that I placed a pull request to the RPi-Jukebox-RFID project which can be found under RPi-Jukebox-RFID Pill request #859.

Currently the decision is that the code cannot be added to the project as we have a license issue. The RPi-Jukebox-RFID projet uses MIT license, see also RPI-Jukebox-RFID License Page. Your driver is released under GPL.

I kindly ask you read the discussion on the pull request page related to the driver scripts/i2c_lcd_driver.py where the license issue is discussed. I hope that you could to a statement, that allows us to use your code in our Jukebox project.

Thank you very much for your help regarding this matter.

Best regards,
Simon

Dear @DenisFromHR ,how can a symbol be updated? For example from this

to this

My code

def get_cpu_temp():
    tmp = open('/sys/class/thermal/thermal_zone0/temp')
    cpu = tmp.read()
    tmp.close()
    return '{:.2f}'.format(float(cpu) / 1000)

mylcd.lcd_load_custom_chars(fontdata2)
mylcd.lcd_display_string(chr(2)+nowtime, 1)
cpu_temp = get_cpu_temp()
    if cpu_temp > 50:
        mylcd.lcd_display_string(chr(1)+cpu_temp, 2)
    else:
        mylcd.lcd_display_string(chr(0)+cpu_temp, 2)

My code work in while True: for update every second
And how i cant disable BACKLIGHT without blink every second?

if  15 < d.hour < 23:
        mylcd.backlight(1)
    else:
        mylcd.backlight(0)

Complete

   def lcd_strobe(self, data):
        d = datetime.now()
 
        if  10 > d.minute > 8:
            self.lcd_device.write_cmd(data | En | LCD_BACKLIGHT)
            sleep(.0005)
            self.lcd_device.write_cmd(((data & ~En) | LCD_BACKLIGHT))
            sleep(.0001)
        else:
            self.lcd_device.write_cmd(data | En | LCD_NOBACKLIGHT)
            sleep(.0005)
            self.lcd_device.write_cmd(((data & ~En) | LCD_NOBACKLIGHT))
            sleep(.0001)

But I still don't understand how to change a character along with a string

Thanks for the libs!

I've spend several hours for trying start libs working.. And I fix it with screwdriver.. Fix potentiometer brightness.

Thanks, I'm new to this stuff, TIL about potentiometer from your comment

Hi Dennis,

Here Ger from Holland.
Can you tell me if you already made a scroll option.
Your scripts are very nice.

Thanks for an answer

Greetings Ger

Hi Dennis,

I'm using your library in my outdoor spa project. It works like a charm!

Thx.

Yves
https://blog.jbip.be/blog/jacuzzi/

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))