Port morse code.

morse/lib/morse.ex

@@ -1,13 +1,67 @@
 defmodule Morse do
+  alias Circuits.GPIO
+
   @moduledoc """
   Functions to control the signal lamp connected with GPIO.
   """
 
+  @relay_pin 17
+  @sleep_short 200
+  @sleep_delay 400
+  @sleep_long 700
+  @sleep_pause 1000
+  @sleep_start 3000
+
+  @on 0
+  @off 1
+
   @doc """
-  Takes a string composed of dots and dashes, and signals them with the
-  signal lamp.
+  Signal the provided symbols using GPIO.
+  Also setup the GPIO.
   """
-  def signal(msg) do
-    IO.puts(msg)
+
+  def signal do
+    case System.get_env("MORSE_MESSAGE") do
+      nil ->
+        # Signal for SOS if the env variable wasn't found :)
+        signal("...---...")
+      message -> signal(message)
+    end
+  end
+
+  def signal(symbols) do
+    {:ok, gpio} = GPIO.open(@relay_pin, :output)
+    GPIO.write(gpio, @off)
+    Process.sleep(@sleep_start)
+    signal_sentence(gpio, String.graphemes(symbols))
+  end
+
+  # Signal a whole sentence of symbols with GPIO.
+  defp signal_sentence(gpio, []) do
+    GPIO.write(gpio, @off)
+    GPIO.close(gpio)
+    :ok
+  end
+
+  defp signal_sentence(gpio, [symbol | rest]) when symbol in [".", "-"] do
+    GPIO.write(gpio, @on)
+    case symbol do
+      "." -> Process.sleep(@sleep_short)
+      "-" -> Process.sleep(@sleep_long)
+    end
+    GPIO.write(gpio, @off)
+
+    Process.sleep(@sleep_delay)
+    signal_sentence(gpio, rest)
+  end
+
+  defp signal_sentence(gpio, [" " | rest]) do
+    Process.sleep(@sleep_pause)
+
+    signal_sentence(gpio, rest)
+  end
+
+  defp signal_sentence(_gpio, [symbol | _rest]) do
+    {:error, "Undefined symbol: " <> symbol}
   end
 end

morse/mix.exs

@@ -21,8 +21,7 @@ defmodule Morse.MixProject do
   # Run "mix help deps" to learn about dependencies.
   defp deps do
     [
-      # {:dep_from_hexpm, "~> 0.3.0"},
-      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+      {:circuits_gpio, "~> 0.4.1"}
     ]
   end
 end

morse/mix.lock

@@ -0,0 +1,4 @@
+%{
+  "circuits_gpio": {:hex, :circuits_gpio, "0.4.1", "344dd34f2517687fd28723e5552571babff5469db05b697181cab860fe7eff23", [:make, :mix], [{:elixir_make, "~> 0.5", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm"},
+  "elixir_make": {:hex, :elixir_make, "0.6.0", "38349f3e29aff4864352084fc736fa7fa0f2995a819a737554f7ebd28b85aaab", [:mix], [], "hexpm"},
+}