diff --git a/boards/nrf5340dk-app/include/periph_conf.h b/boards/nrf5340dk-app/include/periph_conf.h
index ad7880f253fc0..6a673de319ed5 100644
--- a/boards/nrf5340dk-app/include/periph_conf.h
+++ b/boards/nrf5340dk-app/include/periph_conf.h
@@ -80,16 +80,16 @@ static const uart_conf_t uart_config[] = {
  * @{
  */
 #ifndef RTT_DEV
-#define RTT_DEV             (0)                 /* NRF_RTC0_S */
+#define RTT_DEV             (0)                 /**< NRF_RTC0_S */
 #endif
 
-#define RTT_MAX_VALUE       (0x00ffffff)         /* 24bit */
-#define RTT_MAX_FREQUENCY   (32768U)             /* in Hz */
-#define RTT_MIN_FREQUENCY   (8U)                 /* in Hz */
-#define RTT_CLOCK_FREQUENCY (32768U)             /* in Hz, LFCLK*/
+#define RTT_MAX_VALUE       (0x00ffffff)         /**< 24bit */
+#define RTT_MAX_FREQUENCY   (32768U)             /**< in Hz */
+#define RTT_MIN_FREQUENCY   (8U)                 /**< in Hz */
+#define RTT_CLOCK_FREQUENCY (32768U)             /**< in Hz, LFCLK*/
 
 #ifndef RTT_FREQUENCY
-#define RTT_FREQUENCY       (1024U)              /* in Hz */
+#define RTT_FREQUENCY       (1024U)              /**< in Hz */
 #endif
 /** @} */
 
diff --git a/boards/nrf9160dk/include/periph_conf.h b/boards/nrf9160dk/include/periph_conf.h
index 8588365ea3297..9ad5f1f4e3896 100644
--- a/boards/nrf9160dk/include/periph_conf.h
+++ b/boards/nrf9160dk/include/periph_conf.h
@@ -124,16 +124,16 @@ static const uart_conf_t uart_config[] = {
  * @{
  */
 #ifndef RTT_DEV
-#define RTT_DEV             (0)                 /* NRF_RTC0_S */
+#define RTT_DEV             (0)                 /**< NRF_RTC0_S */
 #endif
 
-#define RTT_MAX_VALUE       (0x00ffffff)         /* 24bit */
-#define RTT_MAX_FREQUENCY   (32768U)             /* in Hz */
-#define RTT_MIN_FREQUENCY   (8U)                 /* in Hz */
-#define RTT_CLOCK_FREQUENCY (32768U)             /* in Hz, LFCLK*/
+#define RTT_MAX_VALUE       (0x00ffffff)         /**< 24bit */
+#define RTT_MAX_FREQUENCY   (32768U)             /**< in Hz */
+#define RTT_MIN_FREQUENCY   (8U)                 /**< in Hz */
+#define RTT_CLOCK_FREQUENCY (32768U)             /**< in Hz, LFCLK*/
 
 #ifndef RTT_FREQUENCY
-#define RTT_FREQUENCY       (1024U)              /* in Hz */
+#define RTT_FREQUENCY       (1024U)              /**< in Hz */
 #endif
 /** @} */