LcdDisplay

Hex.pm API docs CI

LcdDisplay allows you to control a Hitachi HD44780-compatible Liquid-crystal display (LCD) in Elixir.

For the specification of the HD44780 LCD, please refer to the HD44780 data sheet.

nerves_hello_lcd_20201213_185620

Installation

You can install LcdDisplay by adding lcd_display to your list of dependencies in mix.exs:

def deps do
  [
    {:lcd_display, "~> 0.1.0"}
  ]
end

Usage

As an example, if you want to control a Hitachi HD44780 type display through the 8-bit I/O expander PCF8574, you can use LcdDisplay.HD44780.PCF8574 module as a display driver.

Start an LCD driver and get a PID

driver_module = LcdDisplay.HD44780.PCF8574

driver_config = %{
  display_name: "display 1", # the identifier
  i2c_bus: "i2c-1",          # I2C bus name
  i2c_address: 0x27,         # 7-bit address
  rows: 2,                   # the number of display rows
  cols: 16,                  # the number of display columns
  font_size: "5x8"           # "5x10" or "5x8"
}

pid = LcdDisplay.start_display(driver_module, driver_config)

The resulting process will be supervised and locally registered under the composite key of the display module and the specified display name.

Many configuration values are optional, falling back to default values. Please refer to each display module documentation.

Run commands

Please refer to the LcdDisplay.HD44780.Driver documentation for supported display commands.

# Print text
LcdDisplay.execute(pid, {:print, "Hello world"})

# Print a character at a time
LcdDisplay.execute(pid, {:print, 0b00110001})
LcdDisplay.execute(pid, {:print, 0b00110000})
LcdDisplay.execute(pid, {:print, 0b00100101})

LcdDisplay.execute(pid, :clear)

Driver modules

Parallel I/O

When you connect an LCD standalone directly to the GPIO pins on your target device, the LcdDisplay.HD44780.GPIO driver module is useful.

Here are some relevant products:

Serial I/O

When you connect an LCD through an I/O expander, one of the following driver modules can be used.

Different products out there use different I/O expanders, so please be aware of which I/O expander you are using if you use something like an I2C backpack. Also the pin assignment between the LCD and the I/O expander is important since this library assumes certain pin assignment based on popular products out there.

It is easy to make your own driver modules in case you want a custom pin assignment, a different I/O expander or some custom features.

Here are some relevant products:

Thanks

Here are my study notes in case they help somebody: