diff --git a/drivers/avr/system.c b/drivers/avr/system.c
index f7b30af..f494d96 100644
--- a/drivers/avr/system.c
+++ b/drivers/avr/system.c
@@ -30,6 +30,7 @@ static void system_watchdog_timer_init (void)
 }
 
 
+/** Initialise clock and disable watchdog timer.  */
 void system_init (void)
 {
     system_clock_init ();
diff --git a/drivers/avr/system.h b/drivers/avr/system.h
index f2e2e92..670542e 100644
--- a/drivers/avr/system.h
+++ b/drivers/avr/system.h
@@ -12,7 +12,7 @@
 typedef uint8_t bool;
 
 
-/* Useful macros.  */
+/** Useful macros.  */
 #define BIT(X) (1 << (X))
 
 #define ARRAY_SIZE(ARRAY) (sizeof (ARRAY) / sizeof (ARRAY[0]))
@@ -20,11 +20,11 @@ typedef uint8_t bool;
 #define  __unused__ __attribute__ ((unused))
 
 
-/* Clock frequency Hz.  */
+/** Clock frequency Hz.  */
 #define F_CPU 8000000
 
 
-/* LED matrix columns.  (Note these are labelled in reverse order on
+/** LED matrix columns.  (Note these are labelled in reverse order on
    the schematic.)  */
 #define LEDMAT_COL1_PIO PC6_PIO
 #define LEDMAT_COL2_PIO PB7_PIO
@@ -34,7 +34,7 @@ typedef uint8_t bool;
 #define LEDMAT_COLS_NUM 5
 
 
-/* LED matrix rows.  */
+/** LED matrix rows.  */
 #define LEDMAT_ROW1_PIO PB6_PIO
 #define LEDMAT_ROW2_PIO PB5_PIO
 #define LEDMAT_ROW3_PIO PB4_PIO 
@@ -45,12 +45,12 @@ typedef uint8_t bool;
 #define LEDMAT_ROWS_NUM 7
 
 
-/* Button.  */
+/** Button.  */
 #define BUTTON1 0
 #define BUTTON1_PIO PD7_PIO
 
 
-/* Navswitch.  */
+/** Navswitch.  */
 #define NAVSWITCH_PUSH_PIO LEDMAT_COL3_PIO
 #define NAVSWITCH_DOWN_PIO NAVSWITCH_PUSH_PIO 
 #define NAVSWITCH_EAST_PIO LEDMAT_COL1_PIO
@@ -59,18 +59,19 @@ typedef uint8_t bool;
 #define NAVSWITCH_SOUTH_PIO LEDMAT_COL5_PIO
 
 
-/* LED (active high).  */
+/** LED (active high).  */
 #define LED1 0
 #define LED1_PIO PC2_PIO
 
 
-/* Infrared transmitter LED and receiver.  */
+/** Infrared transmitter LED and receiver.  */
 #define IR_TX_LOW_PIO PD3_PIO 
 #define IR_TX_HIGH_PIO PD0_PIO
 #define IR_RX_PIO PD2_PIO
 
 #define IR_MODULATION_FREQ 36e3
 
+/** Initialise clock and disable watchdog timer.  */
 void system_init (void);
 
 #endif