A Python port of Arduino's LiquidCrystal that uses PyWiring to access the display through any I/O port
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liquidcrystal
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README.md
setup.py

README.md

LiquidCrystal for Python

A Python port of Arduino's LiquidCrystal library that uses PyWiring to access an HD44780-based LCD display through any supported I/O port.

Make sure PyWiring is installed.

Usage

First, get an instance of any PyWiring I/O port that has at least 6 digital outputs. For example, you can use pywiring.i2c.PCF8574IO for an I²C I/O port or "LCD backpack" based on the PCF8574 (like this one), or pywiring.parport.ParallelIO for a standard parallel port.

from pywiring import i2c
ioi = i2c.PCF8574IO(1, 0x27)
# 1 is the I²C bus, 0x27 is the I/O port address.
# Read the I/O implementation documentation for further info.

Now you only need to pass the I/O implementation instance to liquidcrystal.LiquidCrystal. Make sure your pin numbers are correct. Default values are for the aforementioned LCD backpack. Beware that only 4-bit mode is currently supported. You can set the R/W and the backlight pins (rw and bl) to None if you're not connecting them.

from liquidcrystal import LiquidCrystal
# No argument is required except for the I/O implementation.
# The values shown below are the default ones.
lcd = LiquidCrystal(ioi, en=2, rw=1, rs=0, data=[4, 5, 6, 7], bl=3, cols=16, rows=2)

The LCD will be immediately initialized and ready to use.

Methods

print_str(string)

Prints an ASCII string to the display

set_cursor(row, col)

Moves the cursor to the desired location (locations start from 0).

write(char)

Write a custom character to the display. char must be an integer between 0 and 255.

clear()

Clears the display and moves the cursor to the first location. Also resets any display scrolls.

home()

Moves the cursor to the first location. Also resets any display scrolls.

create_char(location, char)

Create a new custom character. Location (0-7) is the character position in memory. Char is a sequence of integers. Each integers is a binary representation of the character. For example:

char = [
  0b00000,
  0b01010,
  0b11111,
  0b11111,
  0b01110,
  0b00100,
  0b00000,
  0b00000]

lcd.create_char(0, char)

The sample above character is a heart.

A character generator can be found at http://mikeyancey.com/hamcalc/lcd_characters.php.

move_cursor_right(), move_cursor_left()

Move the cursor one character to the desired direction.

scroll_display_right(), scroll_display_left()

Scroll the whole display one character to the desired direction. Cursor position will be affected, reset with home or clear.

send(value, mode=values.FOUR_BITS)

Note: you shouldn't need this method at all. Use it only if you know what you're doing.

Send a value to the display. value must be an integer between 0 and 255. mode can be values.FOUR_BITS, values.DATA or values.COMMAND. In four bit mode, only the lower 4 bits will be sent, with the register select pin low. In data and command mode, the whole byte will be sent, with the rs pin high in data mode or low in command mode.

Properties

If you don't know what properties are, make sure you read this and this. Basically, they just act like attributes, but under the hood there's much more going on.

backlight (default: 255)

Display brightness in a range between 0 and 255. If your I/O port does not support PWM (a.k.a. analogWrite), the backlight will be off if set to 0 or False, and on if greater than 0 or True.

display (default: True)

Show or hide content from the display.

cursor (default: False)

Show or hide the cursor (usually an underscore).

blink (default: False)

Enable or disable cursor blinking (usually a blinking block)

ltr and rtl (default: ltr = True)

Set the character writing direction (left to right, right to left). Note that when one is set to True, the other one is False, and viceversa (they can't both be True, it wouldn't even make sense).

autoscroll (default: False)

This will 'right justify' text from the cursor, if True.