Configuration

keypad is implemented as a __using__ macro so that you can put it in any module you want to handle the keypress events. Because it is small GenServer, it accepts the same options for supervision to configure the child spec and passes them along to GenServer:

defmodule MyModule do
  use Keypad, restart: :transient, shutdown: 10_000
end

It also has its own set of options to pass to configure the keypad connections. At a minimum, you must pass either :size or a custom matrix with :matrix:

• :size - If supplied without :matrix it will select the default matrix for the specified size. The delaration is row x col, so :one_by_four would be 1 row, 4 columns.
  • :four_by_four or "4x4" - Standard 12-digit keypad with A, B, C, and D keys
  • :four_by_three or "4x3" - Standard 12-digit keypad
  • :one_by_four or "1x4"
• :matrix - A custom matrix to use for mapping keypresses to. Will take precedence over :size if supplied
  • Typically, these are binary values. However, these values are pulled from List and in theory can be anything you want. i.e. atom, integer, or even annonymous function
• :row_pins - List of integers which map to corresponding GPIO to set as INPUT pins for keypard rows
  • On raspberry pi, these will also set the internal resistor to PULL_UP and inactive HIGH. For all other hardware, you will probably need to make sure to place some 10K resistors between your pin and ground. see Setup doc for some examples
  • defaults to [17, 27, 23, 24]
• :col_pins - List of integers which map to corresponding GPIO to as OUTPUT pins for keypad columns
  • defaults to [5, 6, 13, 26]

Examples

Using a default matrix with custom row and column pins:

defmodule MyModule do
  use Keypad, row_pins: [22,23,24,25], col_pins: [5,6,7], size: "4x3"

  @impl true
  def handle_keypress(key, state) do
    IO.inspect(key, label: "KEYPRESS: ")
    state
  end
end

Configuring a custom matrix and specific row and column pins:

defmodule MyModule do
  use Keypad, row_pins: [5,6,7], col_pins: [22,23,24,25], matrix: [
    ["c", "o", "o", "l"],
    [:b, :e, :a, :n],
    [1, 2, 3, 4]
  ]

  @impl true
  def handle_keypress(key, state) do
    IO.inspect(key, label: "KEYPRESS: ")
    state
  end
end

Custom matrix using default pins:

defmodule MyModule do
  use Keypad, matrix: [
    ["c", "o", "o", "l"],
    [:b, :e, :a, :n],
    [1, 2, 3, 4].
    ['*', '%', '#', "+"]
  ]

  @impl true
  def handle_keypress(key, state) do
    IO.inspect(key, label: "KEYPRESS: ")
    state
  end
end