fetch relay pin from env

morse/lib/morse.ex

@@ -5,7 +5,6 @@ defmodule Morse do
   Functions to control the signal lamp connected with GPIO.
   """
 
-  @relay_pin 17
   @sleep_short 200
   @sleep_delay 400
   @sleep_long 700
@@ -25,7 +24,7 @@ defmodule Morse do
   end
 
   def signal(symbols) do
-    {:ok, gpio} = GPIO.open(@relay_pin, :output)
+    {:ok, gpio} = GPIO.open(relay_pin(), :output)
     GPIO.write(gpio, @off)
     Process.sleep(@sleep_start)
     signal_sentence(gpio, String.graphemes(symbols))
@@ -40,10 +39,12 @@ defmodule Morse do
 
   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)
@@ -59,4 +60,8 @@ defmodule Morse do
   defp signal_sentence(_gpio, [symbol | _rest]) do
     {:error, "Undefined symbol: " <> symbol}
   end
+
+  defp relay_pin() do
+    Application.fetch_env!(:morse, :relay_pin)
+  end
 end

morse/mix.exs

@@ -15,7 +15,7 @@ defmodule Morse.MixProject do
   def application do
     [
       extra_applications: [:logger],
-      env: [morse_message: "...---..."]
+      env: [morse_message: "...---...", relay_pin: 17]
     ]
   end
 

ui/config/config.exs

@@ -22,6 +22,8 @@ config :logger, :console,
 # Use Jason for JSON parsing in Phoenix
 config :phoenix, :json_library, Jason
 
+config :morse, :relay_pin, 17
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{Mix.env()}.exs"