examples: timers: add timer_periodic_wakeup example

examples/timer_periodic_wakeup/Makefile

@@ -0,0 +1,9 @@
+APPLICATION = timer_periodic_wakeup
+RIOTBASE ?= $(CURDIR)/../..
+BOARD ?= native
+USEMODULE += xtimer
+QUIET ?= 1
+
+FEATURES_REQUIRED += periph_timer
+
+include $(RIOTBASE)/Makefile.include

examples/timer_periodic_wakeup/main.c

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     xtimer_examples
+ * @{
+ *
+ * @file
+ * @brief       example application for setting a periodic wakeup
+ *
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include "xtimer.h"
+
+/* set interval to 1 second */
+#define INTERVAL (1000000U)
+
+int main(void)
+{
+    uint32_t last_wakeup = xtimer_now();
+
+    while(1) {
+        xtimer_usleep_until(&last_wakeup, INTERVAL);
+        printf("slept until %"PRIu32"\n", xtimer_now());
+    }
+
+    return 0;
+}