diff --git a/include/libopencm3/efm32/ezr32wg/timer.h b/include/libopencm3/efm32/ezr32wg/timer.h
index 848d4eaa..439a418e 100644
--- a/include/libopencm3/efm32/ezr32wg/timer.h
+++ b/include/libopencm3/efm32/ezr32wg/timer.h
@@ -1,3 +1,11 @@
+/** @defgroup timer_defines TIMER Defines
+ *
+ * @brief <b>Defined Constants and Types for the TIMER module</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_TIMER_H
-#define LIBOPENCM3_EFM32_EZR32WG_TIMER_H
+#pragma once
 
 #include <libopencm3/efm32/common/timer_common.h>
-
-#endif
diff --git a/include/libopencm3/efm32/hg/timer.h b/include/libopencm3/efm32/hg/timer.h
index 647abe85..9d88c2e2 100644
--- a/include/libopencm3/efm32/hg/timer.h
+++ b/include/libopencm3/efm32/hg/timer.h
@@ -1,3 +1,11 @@
+/** @defgroup timer_defines TIMER Defines
+ *
+ * @brief <b>Defined Constants and Types for the TIMER module</b>
+ *
+ * @ingroup EFM32HG_defines
+ *
+ * LGPL License Terms @ref lgpl_license
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -15,8 +23,7 @@
  * along with this library.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef LIBOPENCM3_TIMER_H
-#define LIBOPENCM3_TIMER_H
+#pragma once
 
 #include <libopencm3/efm32/common/timer_common.h>
 
@@ -27,5 +34,3 @@
 
 /* TIMER_CCx_CTRL */
 #define TIMER_CC_CTRL_PRSCONF		(1 << 28)
-
-#endif
diff --git a/include/libopencm3/efm32/lg/timer.h b/include/libopencm3/efm32/lg/timer.h
index 83c6b20d..aecd0e64 100644
--- a/include/libopencm3/efm32/lg/timer.h
+++ b/include/libopencm3/efm32/lg/timer.h
@@ -1,3 +1,11 @@
+/** @defgroup timer_defines TIMER Defines
+ *
+ * @brief <b>Defined Constants and Types for the TIMER module</b>
+ *
+ * @ingroup EFM32LG_defines
+ *
+ * LGPL License Terms @ref lgpl_license
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -15,9 +23,6 @@
  * along with this library.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef LIBOPENCM3_TIMER_H
-#define LIBOPENCM3_TIMER_H
+#pragma once
 
 #include <libopencm3/efm32/common/timer_common.h>
-
-#endif
diff --git a/include/libopencm3/efm32/wg/timer.h b/include/libopencm3/efm32/wg/timer.h
index fc51e77d..9d0a1cd1 100644
--- a/include/libopencm3/efm32/wg/timer.h
+++ b/include/libopencm3/efm32/wg/timer.h
@@ -1,3 +1,11 @@
+/** @defgroup timer_defines TIMER Defines
+ *
+ * @brief <b>Defined Constants and Types for the TIMER module</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_TIMER_H
-#define LIBOPENCM3_EFM32_WG_TIMER_H
+#pragma once
 
 #include <libopencm3/efm32/common/timer_common.h>
-
-#endif
diff --git a/lib/efm32/common/timer_common.c b/lib/efm32/common/timer_common.c
index 22664954..8f82fcfe 100644
--- a/lib/efm32/common/timer_common.c
+++ b/lib/efm32/common/timer_common.c
@@ -1,3 +1,6 @@
+/** @addtogroup timer_file TIMER peripheral API
+ * @ingroup peripheral_apis
+ */
 /*
  * This file is part of the libopencm3 project.
  *
@@ -19,6 +22,8 @@
 
 #include <libopencm3/efm32/timer.h>
 
+/**@{*/
+
 #define HAS_DEAD_TIME_INSERTION(timer) (timer == TIMER0)
 
 /**
@@ -60,3 +65,5 @@ void timer_set_top(uint32_t timer, uint32_t top)
 {
 	TIMER_TOP(timer) = top;
 }
+
+/**@}*/
\ No newline at end of file