hd44780_basic_driver.ex

# LCD
  def four_bit_init do
    {:ok, rs} = GPIO.open(22, :output)
    {:ok, d4} = GPIO.open(25, :output)
    {:ok, d5} = GPIO.open(24, :output)
    {:ok, d6} = GPIO.open(23, :output)
    {:ok, d7} = GPIO.open(18, :output)


    GPIO.write(rs, 0)
    GPIO.write(d7, 0)
    GPIO.write(d6, 0)
    GPIO.write(d5, 1)
    GPIO.write(d4, 1)

    pulse_en()
    :timer.sleep(5)

    GPIO.write(rs, 0)
    GPIO.write(d7, 0)
    GPIO.write(d6, 0)
    GPIO.write(d5, 1)
    GPIO.write(d4, 1)

    pulse_en()
    :timer.sleep(5)

    GPIO.write(rs, 0)
    GPIO.write(d7, 0)
    GPIO.write(d6, 0)
    GPIO.write(d5, 1)
    GPIO.write(d4, 1)

    pulse_en()
    :timer.sleep(5)

    GPIO.write(rs, 0)
    GPIO.write(d7, 0)
    GPIO.write(d6, 0)
    GPIO.write(d5, 1)
    GPIO.write(d4, 0)

    pulse_en()
    :timer.sleep(5)

    :ok
  end


  def function_set do
    {:ok, rs} = GPIO.open(22, :output)
    {:ok, d4} = GPIO.open(25, :output)
    {:ok, d5} = GPIO.open(24, :output)
    {:ok, d6} = GPIO.open(23, :output)
    {:ok, d7} = GPIO.open(18, :output)


    GPIO.write(rs, 0)
    GPIO.write(d7, 0)
    GPIO.write(d6, 0)
    GPIO.write(d5, 0)
    GPIO.write(d4, 0)

    pulse_en()
    :timer.sleep(5)

    GPIO.write(d7, 1)
    GPIO.write(d6, 1)
    GPIO.write(d5, 1)
    GPIO.write(d4, 1)

    pulse_en()
    :timer.sleep(5)
    :ok
  end

  def blink_cursor do
    write_byte(0xF, 0)
    :ok
  end

  def display_on do
    write_byte(0xC, 0)
    :ok
  end

  def display_off do
    write_byte(0x08, 0)
    :ok
  end

  def set_line_2 do
    write_byte(0x194, 0)
    :ok
  end

  def shift_display_right do
    write_byte(0x18, 0)
    :ok
  end

  def right_entry do
    write_byte(0x01, 0)
    :ok
  end

  def lcd_clear do
    write_byte(0x01, 0)
    :ok
  end

  def lcd_home do
    write_byte(0x02, 0)
    :ok
  end

  def lcd_print(string) do
      String.to_charlist(string)
      |> Enum.each(fn(char) -> write_byte(char, 1) end)
    :ok
  end

  def lcd_2_line_print(line1, line2) do
    padded_line = String.pad_trailing(line1, 40)

    padded_line <> line2
    |> lcd_print()
  end



  def write_byte(byte, rs) do
    write_4_bits(byte >>> 4, rs)

    write_4_bits(byte, rs)
  end

  def write_4_bits(bits, rs_val) do
    {:ok, rs} = GPIO.open(22, :output)
    {:ok, d4} = GPIO.open(25, :output)
    {:ok, d5} = GPIO.open(24, :output)
    {:ok, d6} = GPIO.open(23, :output)
    {:ok, d7} = GPIO.open(18, :output)


    GPIO.write(rs, rs_val)
    GPIO.write(d4, bits &&& 0x01)
    GPIO.write(d5, bits >>> 1 &&& 0x01)
    GPIO.write(d6, bits >>> 2 &&& 0x01)
    GPIO.write(d7, bits >>> 3 &&& 0x01)

    pulse_en()
    :timer.sleep(5)
  end


  def pulse_en do
    {:ok, en} = GPIO.open(17, :output)

    GPIO.write(en, 0)
    GPIO.write(en, 1)
    GPIO.write(en, 0)
  end