This library provides an interface for controlling HD44780-based LCD displays using a PCF8574 I/O expander (often sold as a single module) with a MicroPython-compatible microcontroller. The library is designed to offer high-level functions for LCD control while allowing access to underlying GPIO operations on the PCF8574 when necessary.

The library is structured around several classes, each serving a specific role:

1. BacklightDriver: An abstract base class for controlling the backlight of an LCD display.

2. HD44780: A class for interacting with HD44780 LCD drivers through a PCF8574 I/O expander. Provides methods for writing characters and strings to the LCD, clearing the display, and controlling the display properties.

3. HD447804BitDriver: An abstract base class for controlling the HD44780 LCD controller through a 4-bit data bus.

4. HD447804BitPayload: A class representing data to be written to the HD44780 LCD controller.

5. LCD: A high-level API for controlling HD44780-based LCD displays. This class provides methods to write text to the LCD, control the cursor and display properties, and clear the display.

6. PCF8574: A class for controlling the HD44780 LCD controller through a PCF8574 I/O expander. Implements the HD447804BitController and BacklightDriver interfaces, providing methods for writing 4-bit payloads to the HD44780 LCD controller via the PCF8574, and controlling the LCD's backlight.

7. test_main: Contains a function for testing the library's functionality.

First, import the necessary classes from the library:

from machine import Pin, I2C from pcf8574 import PCF8574 from hd44780 import HD44780 from lcd import LCD

Then, initialize the LCD:

i2c = I2C(0, sda=Pin(0), scl=Pin(1), freq=400000) pcf = PCF8574(i2c) hd44780 = HD44780(pcf, num_lines=2, num_columns=16) lcd = LCD(hd44780, pcf) lcd.backlight_on()

Now you can use the lcd object to control the LCD. For instance, to write a line of text to the display:

lcd.write_line("Hello, world!", 0)

To create a scrolling text:

lcd.marquee_text("Hello...", 1, 0.2)

To control the cursor and display:

lcd.cursor_on() lcd.blink_on() utime.sleep(2) lcd.cursor_off() lcd.blink_off()

And to control the backlight:

lcd.backlight_on() utime.sleep(2) lcd.backlight_off()

Run the main_test function in test_main.py to verify the library's functionality. This function will run a series of tests to demonstrate the capabilities of the library.