Improve 3 Hz blink timing and any odd blink period

Author: Frank Hunleth

lib/delux/effects.ex

@@ -279,8 +279,10 @@ defmodule Delux.Effects do
   defp led_blink(0, _frequency), do: led_off()
 
   defp led_blink(b, frequency) when frequency > 0 and frequency < 20 do
-    on_time = round(500 / frequency)
-    [{b, on_time}, {b, 0}, {0, on_time}, {0, 0}]
+    period = round(1000 / frequency)
+    on_time = div(period, 2)
+    off_time = period - on_time
+    [{b, on_time}, {b, 0}, {0, off_time}, {0, 0}]
   end
 
   defp led_blink(b, frequency) when frequency >= 20, do: led_on(b)

test/delux/effects_test.exs

@@ -67,6 +67,16 @@ defmodule Delux.EffectsTest do
       assert pattern.blue == [{0, 3_600_000}, {0, 0}]
     end
 
+    test "blink period is close" do
+      pattern = Effects.blink(:red, 3)
+
+      # 3 Hz has a ~333 ms period which isn't divisible by 2.
+      # Therefore, on and off times should be different.
+      assert pattern.red == [{1, 166}, {1, 0}, {0, 167}, {0, 0}]
+      assert pattern.green == [{0, 3_600_000}, {0, 0}]
+      assert pattern.blue == [{0, 3_600_000}, {0, 0}]
+    end
+
     test "description" do
       pattern = Effects.blink(:blue, 2)
       assert Program.text_description(pattern) == "blue at 2 Hz"