diff --git a/hw/bsp/metro_m0_express/board_metro_m0_express.c b/hw/bsp/metro_m0_express/board_metro_m0_express.c
index ee0edca74..8876b62bb 100644
--- a/hw/bsp/metro_m0_express/board_metro_m0_express.c
+++ b/hw/bsp/metro_m0_express/board_metro_m0_express.c
@@ -39,7 +39,7 @@
 // MACRO TYPEDEF CONSTANT ENUM DECLARATION
 //--------------------------------------------------------------------+
 #define LED_PIN      17
-#define BUTTON_PIN   14
+#define BUTTON_PIN   14 // pin D2
 
 /* Referenced GCLKs, should be initialized firstly */
 #define _GCLK_INIT_1ST (1 << 0 | 1 << 1)
diff --git a/hw/bsp/metro_m4_express/board_metro_m4_express.c b/hw/bsp/metro_m4_express/board_metro_m4_express.c
index b311aa571..aaaf7c483 100644
--- a/hw/bsp/metro_m4_express/board_metro_m4_express.c
+++ b/hw/bsp/metro_m4_express/board_metro_m4_express.c
@@ -36,7 +36,7 @@
 // MACRO TYPEDEF CONSTANT ENUM DECLARATION
 //--------------------------------------------------------------------+
 #define LED_PIN      16
-#define BUTTON_PIN   (32 + 17)
+#define BUTTON_PIN   (32 + 17)  // pin D2
 
 /* Referenced GCLKs, should be initialized firstly */
 #define _GCLK_INIT_1ST 0xFFFFFFFF