.. note::

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.. _py_lcd:

3.4 Liquid Crystal Display
===============================

LCD1602 is a character type liquid crystal display, which can display 32 (16*2) characters at the same time.

As we all know, though LCD and some other displays greatly enrich the man-machine interaction, 
they share a common weakness. When they are connected to a controller, 
multiple IOs will be occupied of the controller which has no so many outer ports. 
Also it restricts other functions of the controller. 
Therefore, LCD1602 with an I2C bus is developed to solve the problem.

* :ref:`cpn_i2c_lcd`
* `Inter-Integrated Circuit - Wikipedia <https://en.wikipedia.org/wiki/I2C>`_


|pin_i2c|

Here we will use the I2C1 interface to control the LCD1602 and display text.


**Required Components**

In this project, we need the following components. 

It's definitely convenient to buy a whole kit, here's the link: 

.. list-table::
    :widths: 20 20 20
    :header-rows: 1

    *   - Name	
        - ITEMS IN THIS KIT
        - LINK
    *   - Kepler Kit	
        - 450+
        - |link_kepler_kit|

You can also buy them separately from the links below.

.. list-table::
    :widths: 5 20 5 20
    :header-rows: 1

    *   - SN
        - COMPONENT	
        - QUANTITY
        - LINK

    *   - 1
        - :ref:`cpn_pico_w`
        - 1
        - |link_picow_buy|
    *   - 2
        - Micro USB Cable
        - 1
        - 
    *   - 3
        - :ref:`cpn_breadboard`
        - 1
        - |link_breadboard_buy|
    *   - 4
        - :ref:`cpn_wire`
        - Several
        - |link_wires_buy|
    *   - 5
        - :ref:`cpn_i2c_lcd`
        - 1
        - |link_i2clcd1602_buy|

**Schematic**

|sch_lcd|

**Wiring**

|wiring_lcd|

**Code**

.. note::

    * Open the ``3.4_liquid_crystal_display.py`` file under the path of ``kepler-kit-main/micropython`` or copy this code into Thonny, then click "Run Current Script" or simply press F5 to run it.

    * Don't forget to click on the "MicroPython (Raspberry Pi Pico)" interpreter in the bottom right corner. 

    * For detailed tutorials, please refer to :ref:`open_run_code_py`. 
    
    * Here you need to use the library called ``lcd1602.py``, please check if it has been uploaded to Pico W, for a detailed tutorial refer to :ref:`add_libraries_py`.


.. code-block:: python

    from machine import I2C, Pin
    from lcd1602 import LCD
    import time

    # Initialize I2C communication;
    i2c = I2C(1, sda=Pin(6), scl=Pin(7), freq=400000)

    # Create an LCD object for interfacing with the LCD1602 display
    lcd = LCD(i2c)

    # Display the first message on the LCD
    # Use '\n' to create a new line.
    string = "SunFounder\n    LCD Tutorial"
    lcd.message(string)
    # Wait for 2 seconds
    time.sleep(2)
    # Clear the display
    lcd.clear()

    # Display the second message on the LCD
    string = "Hello\n  World!"
    lcd.message(string)
    # Wait for 5 seconds
    time.sleep(5)
    # Clear the display before exiting
    lcd.clear()

After the program runs, you will be able to see two lines of text appear on the LCD in turn, and then disappear.

.. note:: When the code is running, if the screen is blank, you can turn the potentiometer on the back to increase the contrast.

**How it works?**

#. Setting up I2C Communication

   The ``machine`` module is used to set up I2C communication. SDA (Serial Data) and SCL (Serial Clock) pins are defined (pin 20 and 21 respectively), along with the I2C frequency (400kHz).

   .. code-block:: python
      
      from machine import I2C, Pin
      i2c = I2C(1, sda=Pin(6), scl=Pin(7), freq=400000)

#. Initializing the LCD Display

   The ``LCD`` class from the ``lcd1602`` module is instantiated. This class handles the communication with the LCD display through I2C. An ``LCD`` object is created using the ``i2c`` object.

   For more usage of the ``lcd1602`` library, please refer to ``lcd1602.py``.

   .. code-block:: python
      
      from lcd1602 import LCD
      lcd = LCD(i2c)

#. Displaying Messages on the LCD

   The ``message`` method of the ``LCD`` object is used to display text on the screen. The ``\n`` character creates a new line on the LCD. The ``time.sleep()`` function pauses execution for a specified number of seconds.

   .. code-block:: python
      
      string = "SunFounder\n    LCD Tutorial"
      lcd.message(string)
      time.sleep(2)
      lcd.clear()

#. Clearing the Display

   The ``clear`` method of the ``LCD`` object is called to clear the text from the display.

   .. code-block:: python
      
      lcd.clear()

#. Displaying a Second Message

   A new message is displayed, followed by a delay and then clearing the screen again.

   .. code-block:: python
      
      string = "Hello\n  World!"
      lcd.message(string)
      time.sleep(5)
      lcd.clear()