Added Arduino example

examples/Print

@@ -0,0 +1,69 @@
+/*
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * Copyright (c) 2016 Edward Yang
+ * All rights reserved.
+ *
+ */
+
+#include "DS3231.h"
+
+/*
+ * Example program for Arduino
+ */
+
+void setup() {
+    Wire.begin();
+    Serial.begin(9600);
+    // Set the initial time
+    ts t;
+    t.sec = 0;
+    t.min = 0;
+    t.hour = 0;
+    t.dayOfWeek = 4;
+    t.day = 25;
+    t.month = 5;
+    t.year = 16;
+    set(t);
+}
+
+void print(ts t) {
+    Serial.print("20");
+    Serial.print(t.year, DEC);
+    Serial.print("/");
+    Serial.print(t.month, DEC);
+    Serial.print("/");
+    Serial.print(t.day, DEC);
+    Serial.print(" ");
+
+    if (t.hour < 10) {
+        Serial.print("0");
+    }
+    Serial.print(t.hour, DEC);
+    Serial.print(":");
+    if (t.min < 10) {
+        Serial.print("0");
+    }
+    Serial.print(t.min, DEC);
+    Serial.print(":");
+    if (t.sec < 10) {
+        Serial.print("0");
+    }
+    Serial.print(t.sec, DEC);
+    Serial.print("\n");
+}
+
+void loop() {
+    ts t;
+    get(&t);
+    print(t);
+    delay(1000);
+}

lib/ds3231.h

@@ -26,7 +26,7 @@ struct ts {
     uint8_t sec;
     uint8_t min;
     uint8_t hour;
-    uint8_t dayOfWeek;
+    uint8_t dayOfWeek; // 1 = Sunday, 7 = Saturday
     uint8_t day;
     uint8_t month;
     uint8_t year;