diff --git a/include/libopencm3/efm32/common/rtc_common.h b/include/libopencm3/efm32/common/rtc_common.h
index ad50bcbd..c7eea3e4 100644
--- a/include/libopencm3/efm32/common/rtc_common.h
+++ b/include/libopencm3/efm32/common/rtc_common.h
@@ -1,3 +1,5 @@
+/** @addtogroup rtc_defines
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -17,12 +19,13 @@
  * along with this library.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef LIBOPENCM3_EFM32_RTC_H
-#define LIBOPENCM3_EFM32_RTC_H
+#pragma once
 
 #include <libopencm3/efm32/memorymap.h>
 #include <libopencm3/cm3/common.h>
 
+/**@{*/
+
 #define RTC_CTRL		(RTC_BASE + 0x000)
 #define RTC_CNT			(RTC_BASE + 0x004)
 #define RTC_COMP0		(RTC_BASE + 0x008)
@@ -67,5 +70,4 @@
 #define RTC_SYNCBUSY_COMP0		(1 << 1)
 #define RTC_SYNCBUSY_CTRL		(1 << 0)
 
-#endif
-
+/**@}*/
\ No newline at end of file
diff --git a/include/libopencm3/efm32/ezr32wg/rtc.h b/include/libopencm3/efm32/ezr32wg/rtc.h
index 3c96410c..a45a5e72 100644
--- a/include/libopencm3/efm32/ezr32wg/rtc.h
+++ b/include/libopencm3/efm32/ezr32wg/rtc.h
@@ -1,3 +1,11 @@
+/** @defgroup rtc_defines RTC Defines
+ *
+ * @brief <b>Defined Constants and Types for the Real Time Clock</b>
+ *
+ * @ingroup EZR32WG_defines
+ *
+ * LGPL License Terms @ref lgpl_license
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -17,9 +25,6 @@
  * along with this library.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef LIBOPENCM3_EFM32_EZR32WG_RTC_H
-#define LIBOPENCM3_EFM32_EZR32WG_RTC_H
+#pragma once
 
 #include <libopencm3/efm32/common/rtc_common.h>
-
-#endif
diff --git a/include/libopencm3/efm32/lg/rtc.h b/include/libopencm3/efm32/lg/rtc.h
index 49b2abaa..0aab324e 100644
--- a/include/libopencm3/efm32/lg/rtc.h
+++ b/include/libopencm3/efm32/lg/rtc.h
@@ -1,3 +1,11 @@
+/** @defgroup rtc_defines RTC Defines
+ *
+ * @brief <b>Defined Constants and Types for the Real Time Clock</b>
+ *
+ * @ingroup EFM32LG_defines
+ *
+ * LGPL License Terms @ref lgpl_license
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -17,9 +25,6 @@
  * along with this library.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef LIBOPENCM3_EFM32_LG_RTC_H
-#define LIBOPENCM3_EFM32_LG_RTC_H
+#pragma once
 
 #include <libopencm3/efm32/common/rtc_common.h>
-
-#endif
diff --git a/include/libopencm3/efm32/wg/rtc.h b/include/libopencm3/efm32/wg/rtc.h
index 39c2ff0e..e2a85a66 100644
--- a/include/libopencm3/efm32/wg/rtc.h
+++ b/include/libopencm3/efm32/wg/rtc.h
@@ -1,3 +1,11 @@
+/** @defgroup rtc_defines RTC Defines
+ *
+ * @brief <b>Defined Constants and Types for the Real Time Clock</b>
+ *
+ * @ingroup EFM32WG_defines
+ *
+ * LGPL License Terms @ref lgpl_license
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -17,9 +25,6 @@
  * along with this library.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef LIBOPENCM3_EFM32_WG_RTC_H
-#define LIBOPENCM3_EFM32_WG_RTC_H
+#pragma once
 
 #include <libopencm3/efm32/common/rtc_common.h>
-
-#endif
diff --git a/lib/efm32/common/rtc_common.c b/lib/efm32/common/rtc_common.c
new file mode 100644
index 00000000..b7898ae6
--- /dev/null
+++ b/lib/efm32/common/rtc_common.c
@@ -0,0 +1,16 @@
+/** @addtogroup rtc_file RTC peripheral API
+ * @ingroup peripheral_apis
+ * @brief Real Time Clock helper functions.
+ *
+ * <b>NO</b> helper functions exist. Only header definitions are available.
+ * Delete these lines if/when you add actual helper APIs.
+ * @sa rtc_defines
+ * @copyright See @ref lgpl_license
+ */
+
+#include <libopencm3/efm32/rtc.h>
+
+/**@{*/
+
+/**@}*/
+
diff --git a/lib/efm32/ezr32wg/Makefile b/lib/efm32/ezr32wg/Makefile
index f2c8e962..78ee2db1 100644
--- a/lib/efm32/ezr32wg/Makefile
+++ b/lib/efm32/ezr32wg/Makefile
@@ -50,6 +50,7 @@ OBJS += letimer_common.o
 OBJS += msc_common.o
 OBJS += prs_common.o
 OBJS += rmu_common.o
+OBJS += rtc_common.o
 OBJS += timer_common.o
 OBJS += wdog_common.o
 
diff --git a/lib/efm32/lg/Makefile b/lib/efm32/lg/Makefile
index 30c747a9..cf1e5bc9 100644
--- a/lib/efm32/lg/Makefile
+++ b/lib/efm32/lg/Makefile
@@ -50,6 +50,7 @@ OBJS += letimer_common.o
 OBJS += msc_common.o
 OBJS += prs_common.o
 OBJS += rmu_common.o
+OBJS += rtc_common.o
 OBJS += timer_common.o
 OBJS += wdog_common.o
 
diff --git a/lib/efm32/wg/Makefile b/lib/efm32/wg/Makefile
index d0f45a0b..ef4b264f 100644
--- a/lib/efm32/wg/Makefile
+++ b/lib/efm32/wg/Makefile
@@ -50,6 +50,7 @@ OBJS += letimer_common.o
 OBJS += msc_common.o
 OBJS += prs_common.o
 OBJS += rmu_common.o
+OBJS += rtc_common.o
 OBJS += timer_common.o
 OBJS += wdog_common.o