diff --git a/firmware/main.c b/firmware/main.c
index 2ce7961..9e30e15 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -11,7 +11,8 @@
 
 #include "main.h"
 
-// Main loop
+/*! \brief Main loop
+ */
 int __attribute__((OS_main))
 main()
 {
@@ -26,7 +27,8 @@ main()
     }
 }
 
-// Initialize the AVR.
+/*! \brief Initialize the AVR.
+ */
 void init()
 {
     // Init ports
@@ -52,7 +54,8 @@ void init()
     sei(); // Enable interrupts global
 }
 
-// TIMER1 interruptvector
+/*! \brief TIMER1 interruptvector
+ */
 ISR (TIMER1_COMPA_vect)
 {
 
diff --git a/firmware/main.h b/firmware/main.h
index 4556b11..9253f43 100644
--- a/firmware/main.h
+++ b/firmware/main.h
@@ -19,12 +19,13 @@
 #include <avr/io.h>
 #include <avr/eeprom.h>
 
-// Cube-Data
-// bit  0 -  8 = level 1
-// bit  9 - 17 = level 2
-// bit 18 - 26 = level 3
-// bit 27 - 31 = The delay in ISR calls multiplied with 8 until
-//               the next frame will be shown (load from the EEPROM)
+/*! \brief Cube-Data
+ * bit  0 -  8 = level 1
+ * bit  9 - 17 = level 2
+ * bit 18 - 26 = level 3
+ * bit 27 - 31 = The delay in ISR calls multiplied with 8 until
+ *               the next frame will be shown (load from the EEPROM)
+ */
 uint32_t frame;
 
 uint8_t level; // current layer
diff --git a/firmware/usb.c b/firmware/usb.c
index 749b894..dbe3edb 100644
--- a/firmware/usb.c
+++ b/firmware/usb.c
@@ -14,6 +14,10 @@
 
 /* ------------------------------------------------------------------------- */
 
+/*! \brief
+ *  \param USB Data packet.
+ *  \return The length of the received or send data.
+ */
 usbMsgLen_t usbFunctionSetup(uchar data[8])
 {
     usbRequest_t *rq = (void *)data;
@@ -57,6 +61,8 @@ usbMsgLen_t usbFunctionSetup(uchar data[8])
 
 /* ------------------------------------------------------------------------- */
 
+/*! \brief Initializes the USB conneciton.
+ */
 void init_usb(void)
 {