diff --git a/configs/stm32butterfly2/include/board.h b/configs/stm32butterfly2/include/board.h
index 761c0cf6a9d..841c1d8ca0b 100644
--- a/configs/stm32butterfly2/include/board.h
+++ b/configs/stm32butterfly2/include/board.h
@@ -182,14 +182,6 @@ extern "C" {
  * Public Function Prototypes
  ******************************************************************************/
 
-/*******************************************************************************
- * Name: stm32_led_initialize
- *
- * Description:
- *      Initializes board specific LEDS
- ******************************************************************************/
-void stm32_led_initialize(void);
-
 /*******************************************************************************
  * Name: stm32_boardinitialize
  *
@@ -199,6 +191,7 @@ void stm32_led_initialize(void);
  *     has been configured and mapped but before any devices have been
  *     initialized.
  ******************************************************************************/
+
 EXTERN void stm32_boardinitialize(void);
 
 #undef EXTERN
diff --git a/configs/stm32butterfly2/src/stm32_adc.c b/configs/stm32butterfly2/src/stm32_adc.c
index 02fa3fe2387..148287c2488 100644
--- a/configs/stm32butterfly2/src/stm32_adc.c
+++ b/configs/stm32butterfly2/src/stm32_adc.c
@@ -1,4 +1,4 @@
-/*******************************************************************************
+/*****************************************************************************
  * configs/stm32butterfly2/src/stm32_adc.c
  *
  *   Copyright (C) 2016 Michał Łyszczek. All rights reserved.
@@ -30,22 +30,28 @@
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
- *
- ******************************************************************************/
+ ****************************************************************************/
 
-/*******************************************************************************
+/*****************************************************************************
  * Included Files
- ******************************************************************************/
+ ****************************************************************************/
 
 #include <chip.h>
 #include <debug.h>
 #include <errno.h>
-#include <nuttx/config.h>
-#include <stm32_adc.h>
 
-/*******************************************************************************
+#include "stm32_adc.h"
+
+/*****************************************************************************
  * Public Functions
- ******************************************************************************/
+ ****************************************************************************/
+
+/*****************************************************************************
+ * Name: board_adc_setup
+ *
+ * Description:
+ *   Function initializes channel 1 of adc1 and registers device as /dev/adc0
+ ****************************************************************************/
 
 int board_adc_setup(void)
 {
@@ -60,8 +66,7 @@ int board_adc_setup(void)
     }
 
   stm32_configgpio(GPIO_ADC12_IN10);
-  adc = stm32_adcinitialize(1, channel, 1);
-  if (adc == NULL)
+  if ((adc = stm32_adcinitialize(1, channel, 1)) == NULL)
     {
       aerr("ERROR: Failed to get adc interface\n");
       return -ENODEV;
@@ -76,3 +81,4 @@ int board_adc_setup(void)
   initialized = true;
   return OK;
 }
+
diff --git a/configs/stm32butterfly2/src/stm32_boot.c b/configs/stm32butterfly2/src/stm32_boot.c
index 9bba1b7917e..e77a6edffc7 100644
--- a/configs/stm32butterfly2/src/stm32_boot.c
+++ b/configs/stm32butterfly2/src/stm32_boot.c
@@ -1,4 +1,4 @@
-/*******************************************************************************
+/*****************************************************************************
  * configs/stm32butterfly2/src/boot.c
  *
  *   Copyright (C) 2016 Michał Łyszczek. All rights reserved.
@@ -30,23 +30,28 @@
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
- *
- ******************************************************************************/
+ ****************************************************************************/
 
-/*******************************************************************************
+/*****************************************************************************
  * Included Files
- ******************************************************************************/
+ ****************************************************************************/
 
 #include <nuttx/config.h>
 #include <arch/board/board.h>
 #include <syslog.h>
 
-#include "stm32_gpio.h"
 #include "stm32_butterfly2.h"
 
-/*******************************************************************************
+/*****************************************************************************
  * Public Functions
- ******************************************************************************/
+ ****************************************************************************/
+
+/*****************************************************************************
+ * Name: stm32_boardinitialize
+ *
+ * Description:
+ *   Initializes low level pins for the drivers.
+ ****************************************************************************/
 
 void stm32_boardinitialize(void)
 {
@@ -55,20 +60,35 @@ void stm32_boardinitialize(void)
   stm32_usb_initialize();
 }
 
+/*****************************************************************************
+ * Name: board_app_initialize
+ *
+ * Description:
+ *   Initializes upper half drivers with board specific settings
+ *
+ * Returned value:
+ *   0 on sucess or errno value of failed init function.
+ ****************************************************************************/
+
 int board_app_initialize(uintptr_t arg)
 {
-  int rv;
-  if ((rv = stm32_sdinitialize(CONFIG_NSH_MMCSDMINOR)) < 0)
+  int rv = 0;
+
+#ifdef CONFIG_MMCSD
+  if ((rv = stm32_mmcsd_initialize(CONFIG_NSH_MMCSDMINOR)) < 0)
     {
       syslog(LOG_ERR, "Failed to initialize SD slot %d: %d\n");
       return rv;
     }
+#endif
 
+#ifdef CONFIG_USBHOST
   if ((rv = stm32_usbhost_initialize()) < 0)
     {
       syslog(LOG_ERR, "ERROR: Failed to initialize USB host: %d\n", rv);
       return rv;
     }
+#endif
 
-  return 0;
+  return rv;
 }
diff --git a/configs/stm32butterfly2/src/stm32_butterfly2.h b/configs/stm32butterfly2/src/stm32_butterfly2.h
index 849aed137a2..0fa7fd5b197 100644
--- a/configs/stm32butterfly2/src/stm32_butterfly2.h
+++ b/configs/stm32butterfly2/src/stm32_butterfly2.h
@@ -30,7 +30,6 @@
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
- *
  ****************************************************************************/
 
 /*****************************************************************************
@@ -59,6 +58,15 @@
  * Public Functions
  ****************************************************************************/
 
+/*****************************************************************************
+ * Name: stm32_led_initialize
+ *
+ * Description:
+ *      Initializes low level gpio pins for board LEDS
+ ****************************************************************************/
+
+void stm32_led_initialize(void);
+
 /*****************************************************************************
  * Name: stm32_spidev_initialize
  *
@@ -70,17 +78,25 @@
  *   itself.
  ****************************************************************************/
 
+#ifdef CONFIG_STM32_SPI1
 void stm32_spidev_initialize(void);
+#else
+static inline void stm32_spidev_initialize(void);
+#endif
 
 /*****************************************************************************
- * Name: stm32_sdinitialize
+ * Name: stm32_mmcsd_initialize
  *
  * Description:
  *   Initializes SPI-based SD card
  *
  ****************************************************************************/
 
-int stm32_sdinitialize(int minor);
+#ifdef CONFIG_MMCSD
+int stm32_mmcsd_initialize(int minor);
+#else
+static inline int stm32_mmcsd_initialize(int minor);
+#endif
 
 /*****************************************************************************
  * Name: stm32_usb_initialize
diff --git a/configs/stm32butterfly2/src/stm32_leds.c b/configs/stm32butterfly2/src/stm32_leds.c
index 46ac5e6ff4f..98f527e24cd 100644
--- a/configs/stm32butterfly2/src/stm32_leds.c
+++ b/configs/stm32butterfly2/src/stm32_leds.c
@@ -1,5 +1,5 @@
-/*******************************************************************************
- * configs/stm32butterfly2/src/led.c
+/*****************************************************************************
+ * configs/stm32butterfly2/src/stm32_led.c
  *
  *   Copyright (C) 2016 Michał Łyszczek. All rights reserved.
  *   Author: Michał Łyszczek <michal.lyszczek@gmail.com>
@@ -31,26 +31,22 @@
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  *
- ******************************************************************************/
+ ****************************************************************************/
 
-/*******************************************************************************
+/*****************************************************************************
  * Included Files
- ******************************************************************************/
-
-#include <nuttx/config.h>
-
-#include <stdint.h>
-#include <stdbool.h>
+ ****************************************************************************/
 
 #include <nuttx/board.h>
-#include <arch/board/board.h>
-#include <debug.h>
+#include <nuttx/config.h>
+#include <stdbool.h>
+#include <stdint.h>
 
 #include "stm32_gpio.h"
 
-/*******************************************************************************
+/*****************************************************************************
  * Pre-processor definitions
- ******************************************************************************/
+ ****************************************************************************/
 
 #define GPIO_LED1       (GPIO_OUTPUT | GPIO_CNF_OUTPP | GPIO_MODE_50MHz |\
                          GPIO_OUTPUT_SET | GPIO_PORTB | GPIO_PIN0)
@@ -61,9 +57,9 @@
 #define GPIO_LED4       (GPIO_OUTPUT | GPIO_CNF_OUTPP | GPIO_MODE_50MHz |\
                          GPIO_OUTPUT_SET | GPIO_PORTC | GPIO_PIN5)
 
-/*******************************************************************************
+/*****************************************************************************
  * Private Types
- ******************************************************************************/
+ ****************************************************************************/
 
 /* Identifies led state */
 enum led_state
@@ -72,9 +68,16 @@ enum led_state
   LED_OFF = true
 };
 
-/*******************************************************************************
+/*****************************************************************************
  * Private Functions
- ******************************************************************************/
+ ****************************************************************************/
+
+/*****************************************************************************
+ * Name: led_state
+ *
+ * Description:
+ *   Sets pack of leds to given state
+ ****************************************************************************/
 
 static void led_state(enum led_state state, unsigned int leds)
 {
@@ -87,7 +90,7 @@ static void led_state(enum led_state state, unsigned int leds)
     {
       stm32_gpiowrite(GPIO_LED2, state);
     }
-  
+
   if (leds & BOARD_LED3_BIT)
     {
       stm32_gpiowrite(GPIO_LED3, state);
@@ -99,9 +102,16 @@ static void led_state(enum led_state state, unsigned int leds)
     }
 }
 
-/*******************************************************************************
+/*****************************************************************************
  * Public Functions
- ******************************************************************************/
+ ****************************************************************************/
+
+/*****************************************************************************
+ * Name: stm32_led_initialize
+ *
+ * Description:
+ *   Initializes low level gpio pins for board LEDS
+ ****************************************************************************/
 
 void stm32_led_initialize(void)
 {
@@ -112,6 +122,17 @@ void stm32_led_initialize(void)
 }
 
 #ifdef CONFIG_ARCH_LEDS
+
+/*****************************************************************************
+ * Name: board_autoled_on
+ *
+ * Description:
+ *   Drives board leds when specific RTOS state led occurs.
+ *
+ * Input parameters:
+ *   led - This is actually an RTOS state not led number of anything like that
+ ****************************************************************************/
+
 void board_autoled_on(int led)
 {
   switch (led)
@@ -145,6 +166,16 @@ void board_autoled_on(int led)
     }
 }
 
+/*****************************************************************************
+ * Name: board_autoled_off
+ *
+ * Description:
+ *   Drives board leds when specific RTOS state led ends
+ *
+ * Input parameters:
+ *   led - This is actually an RTOS state not led number of anything like that
+ ****************************************************************************/
+
 void board_autoled_off(int led)
 {
   switch (led)
@@ -172,11 +203,32 @@ void board_autoled_off(int led)
 }
 #endif
 
+/*****************************************************************************
+ * Name: board_userled_initialize
+ *
+ * Description:
+ *   This function should initialize leds for user use, but on RTOS start we
+ *   initialize every led for use by RTOS and at end, when RTOS is fully
+ *   booted up, we give control of these specific leds for user. So that's why
+ *   this function is empty.
+ ****************************************************************************/
+
 void board_userled_initialize(void)
 {
   /* Already initialized by stm32_led_initialize. */
 }
 
+/*****************************************************************************
+ * Name: board_userled
+ *
+ * Description:
+ *   Sets led to ledon state.
+ *
+ * Input parameters:
+ *   led - Led to be set, indexed from 0
+ *   ledon - new state for the led.
+ ****************************************************************************/
+
 void board_userled(int led, bool ledon)
 {
 #ifndef CONFIG_ARCH_LEDS
@@ -186,9 +238,19 @@ void board_userled(int led, bool ledon)
     }
 #endif
   unsigned int ledbit = 1 << led;
-  led_state(ledon, ledbit); 
+  led_state(ledon, ledbit);
 }
 
+/*****************************************************************************
+ * Name: board_userled_all
+ *
+ * Description:
+ *   Sets whole ledset to given state.
+ *
+ * Input parameters:
+ *   ledset - Led bits to be set on or off
+ ****************************************************************************/
+
 void board_userled_all(uint8_t ledset)
 {
 #ifdef CONFIG_ARCH_LEDS
@@ -199,3 +261,4 @@ void board_userled_all(uint8_t ledset)
   led_state(led_OFF, ~ledset);
 #endif
 }
+
diff --git a/configs/stm32butterfly2/src/stm32_mmcsd.c b/configs/stm32butterfly2/src/stm32_mmcsd.c
index 104de4b2eec..a127fe16678 100644
--- a/configs/stm32butterfly2/src/stm32_mmcsd.c
+++ b/configs/stm32butterfly2/src/stm32_mmcsd.c
@@ -37,8 +37,6 @@
  * Included Files
  ****************************************************************************/
 
-#include <debug.h>
-#include <fcntl.h>
 #include <nuttx/config.h>
 #include <nuttx/mmcsd.h>
 #include <nuttx/spi/spi.h>
@@ -72,15 +70,15 @@ static const int SD_SLOT_NO = 0;  /* There is only one SD slot */
 
 /* Media changed callback */
 
-static spi_mediachange_t mediachangeclbk;
+static spi_mediachange_t g_chmediaclbk;
 
 /* Argument for media changed callback */
 
-static void *mediachangearg;
+static void *chmediaarg;
 
 /* Semafor to inform stm32_cd_thread that card was inserted or pulled out */
 
-static sem_t cdsem;
+static sem_t g_cdsem;
 
 /*****************************************************************************
  * Private Functions
@@ -90,8 +88,8 @@ static sem_t cdsem;
  * Name: stm32_cd_thread
  *
  * Description:
- *      Working thread to call mediachanged function when card is inserted or
- *      pulled out.
+ *   Working thread to call mediachanged function when card is inserted or
+ *   pulled out.
  ****************************************************************************/
 
 static void *stm32_cd_thread(void *arg)
@@ -100,16 +98,16 @@ static void *stm32_cd_thread(void *arg)
 
   while (1)
     {
-      sem_wait(&cdsem);
+      sem_wait(&g_cdsem);
 
-      if (mediachangeclbk)
+      if (g_chmediaclbk)
         {
           /* Card doesn't seem to initialize properly without letting it to
            * rest for a millsecond or so.
            */
 
           usleep(1 * 1000);
-          mediachangeclbk(mediachangearg);
+          g_chmediaclbk(chmediaarg);
         }
     }
 
@@ -120,7 +118,7 @@ static void *stm32_cd_thread(void *arg)
  * Name: stm32_cd
  *
  * Description:
- *      Card detect interrupt handler.
+ *   Card detect interrupt handler.
  ****************************************************************************/
 
 static int stm32_cd(int irq, FAR void *context)
@@ -128,8 +126,8 @@ static int stm32_cd(int irq, FAR void *context)
   static const int debounce_time = 100; /* [ms] */
   static uint32_t now = 0;
   static uint32_t prev = 0;
-
   struct timespec tp;
+
   clock_gettime(CLOCK_MONOTONIC, &tp);
   now = tp.tv_sec * 1000 + tp.tv_nsec / 1000000;
 
@@ -141,7 +139,7 @@ static int stm32_cd(int irq, FAR void *context)
   if (now - debounce_time > prev)
     {
       prev = now;
-      sem_post(&cdsem);
+      sem_post(&g_cdsem);
     }
 
   return OK;
@@ -155,31 +153,32 @@ static int stm32_cd(int irq, FAR void *context)
  * Name: stm32_spi1register
  *
  * Description:
- *      Registers media change callback
+ *   Registers media change callback
  ****************************************************************************/
 
 int stm32_spi1register(FAR struct spi_dev_s *dev, spi_mediachange_t callback,
                        FAR void *arg)
 {
-  mediachangeclbk = callback;
-  mediachangearg = arg;
+  g_chmediaclbk = callback;
+  chmediaarg = arg;
   return OK;
 }
 
 /*****************************************************************************
- * Name: stm32_sdinitialize
+ * Name: stm32_mmcsd_initialize
  *
  * Description:
- *      Initialize SPI-based SD card and card detect thread.
+ *   Initialize SPI-based SD card and card detect thread.
  ****************************************************************************/
 
-int stm32_sdinitialize(int minor)
+int stm32_mmcsd_initialize(int minor)
 {
   FAR struct spi_dev_s *spi;
+  struct sched_param schparam;
+  pthread_attr_t pattr;
   int rv;
 
-  spi = stm32_spibus_initialize(SD_SPI_PORT);
-  if (!spi)
+  if ((spi = stm32_spibus_initialize(SD_SPI_PORT)) == NULL)
     {
       ferr("failed to initialize SPI port %d\n", SD_SPI_PORT);
       return -ENODEV;
@@ -193,15 +192,18 @@ int stm32_sdinitialize(int minor)
     }
 
   stm32_gpiosetevent(GPIO_SD_CD, true, true, true, stm32_cd);
-  sem_init(&cdsem, 0, 0);
 
-  pthread_attr_t pattr;
+  sem_init(&g_cdsem, 0, 0);
   pthread_attr_init(&pattr);
+
 #ifdef CONFIG_DEBUG_FS
   pthread_attr_setstacksize(&pattr, 1024);
 #else
   pthread_attr_setstacksize(&pattr, 256);
 #endif
+
+  schparam.sched_priority = 50;
+  pthread_attr_setschedparam(&pattr, &schedparam);
   pthread_create(NULL, &pattr, stm32_cd_thread, NULL);
 
   return OK;
diff --git a/configs/stm32butterfly2/src/stm32_spi.c b/configs/stm32butterfly2/src/stm32_spi.c
index de3f77538dc..35400e35506 100644
--- a/configs/stm32butterfly2/src/stm32_spi.c
+++ b/configs/stm32butterfly2/src/stm32_spi.c
@@ -36,8 +36,6 @@
  * Included Files
  ****************************************************************************/
 
-#include <debug.h>
-#include <nuttx/config.h>
 #include <nuttx/spi/spi.h>
 
 #include "stm32_butterfly2.h"
@@ -52,11 +50,11 @@
  * Name: stm32_spidev_initialize
  *
  * Description:
- *      Called to configure SPI chip select GPIO pins.
+ *   Called to configure SPI chip select GPIO pins.
  *
  * Note:
- *      Here only CS pins are configured as SPI pins are configured by driver
- *      itself.
+ *   Here only CS pins are configured as SPI pins are configured by driver
+ *   itself.
  ****************************************************************************/
 
 void stm32_spidev_initialize(void)
@@ -69,7 +67,7 @@ void stm32_spidev_initialize(void)
  * Name: stm32_spi1select
  *
  * Description:
- *      Function asserts given devid based on select
+ *   Function asserts given devid based on select
  ****************************************************************************/
 
 void stm32_spi1select(FAR struct spi_dev_s *dev, enum spi_dev_e devid,
@@ -85,7 +83,7 @@ void stm32_spi1select(FAR struct spi_dev_s *dev, enum spi_dev_e devid,
  * Name: stm32_spi1status
  *
  * Description:
- *      Return status of devid
+ *   Return status of devid
  ****************************************************************************/
 
 uint8_t stm32_spi1status(FAR struct spi_dev_s *dev, enum spi_dev_e devid)
diff --git a/configs/stm32butterfly2/src/stm32_usb.c b/configs/stm32butterfly2/src/stm32_usb.c
index b9185f58874..4556bec410f 100644
--- a/configs/stm32butterfly2/src/stm32_usb.c
+++ b/configs/stm32butterfly2/src/stm32_usb.c
@@ -37,8 +37,7 @@
  * Include Files
  ****************************************************************************/
 
-#include <stm32_gpio.h>
-#include <stm32_otgfs.h>
+#include "stm32_gpio.h"
 
 #include "stm32_butterfly2.h"
 
diff --git a/configs/stm32butterfly2/src/stm32_usbhost.c b/configs/stm32butterfly2/src/stm32_usbhost.c
index 6bbefec07da..592e3e034c2 100644
--- a/configs/stm32butterfly2/src/stm32_usbhost.c
+++ b/configs/stm32butterfly2/src/stm32_usbhost.c
@@ -1,5 +1,5 @@
 /*****************************************************************************
- * configs/stm32butterfly2/src/stm32_usb.c
+ * configs/stm32butterfly2/src/stm32_usbhost.c
  *
  *   Copyright (C) 2016 Michał Łyszczek. All rights reserved.
  *   Author: Michał Łyszczek <michal.lyszczek@gmail.com>
@@ -37,8 +37,6 @@
  * Include Files
  ****************************************************************************/
 
-#include <assert.h>
-#include <debug.h>
 #include <errno.h>
 #include <nuttx/config.h>
 #include <nuttx/usb/usbhost.h>
@@ -79,7 +77,6 @@ static struct usbhost_connection_s *g_usbconn;
 static void* usbhost_detect(void *arg)
 {
   (void)arg;
-
   struct usbhost_hubport_s *hport;
 
   for (;;)
@@ -176,8 +173,6 @@ int stm32_usbhost_initialize(void)
 
 void stm32_usbhost_vbusdrive(int iface, bool enable)
 {
-  DEBUGASSERT(iface == 0);
-
   stm32_gpiowrite(GPIO_OTGFS_PWRON, enable);
 }