diff --git a/src/boards.h b/src/boards.h
index 595f232..4a658ec 100644
--- a/src/boards.h
+++ b/src/boards.h
@@ -33,6 +33,10 @@
 
 #include "board.h"
 
+#ifndef UF2_VOLUME_LABEL
+#define UF2_VOLUME_LABEL   "NRF52BOOT  "
+#endif
+
 #ifndef BUTTON_DFU
 #define BUTTON_DFU      BUTTON_1
 #endif
diff --git a/src/usb/uf2/ghostfat.c b/src/usb/uf2/ghostfat.c
index de0f02c..1180214 100644
--- a/src/usb/uf2/ghostfat.c
+++ b/src/usb/uf2/ghostfat.c
@@ -102,7 +102,7 @@ STATIC_ASSERT(ARRAY_SIZE(indexFile) < 512);
 #define NUM_FILES (ARRAY_SIZE(info))
 #define NUM_DIRENTRIES (NUM_FILES + 1) // Code adds volume label as first root directory entry
 
-#define UF2_SIZE           (current_flash_size() * 2)
+#define UF2_SIZE           (uf2current_flash_sz * 2)
 #define UF2_SECTORS        (UF2_SIZE / 512)
 #define UF2_FIRST_SECTOR   (NUM_FILES + 1) // WARNING -- code presumes each non-UF2 file content fits in single sector
 #define UF2_LAST_SECTOR    (UF2_FIRST_SECTOR + UF2_SECTORS - 1)
@@ -146,48 +146,48 @@ static FAT_BootBlock const BootBlock = {
 //--------------------------------------------------------------------+
 //
 //--------------------------------------------------------------------+
+static uint32_t uf2current_flash_sz = 0;
+
 
 // get current.uf2 flash size in bytes, round up to 256 bytes
 static uint32_t current_flash_size(void)
 {
-  static uint32_t flash_sz = 0;
-  uint32_t result = flash_sz; // presumes atomic 32-bit read/write and static result
+  uint32_t flash_sz = 0;
 
-  // only need to compute once
-  if ( result == 0 )
+  // return 1 block of 256 bytes
+  if ( !bootloader_app_is_valid(DFU_BANK_0_REGION_START) )
   {
-    // return 1 block of 256 bytes
-    if ( !bootloader_app_is_valid(DFU_BANK_0_REGION_START) )
+    flash_sz = 256;
+  }else
+  {
+    bootloader_settings_t const * boot_setting;
+    bootloader_util_settings_get(&boot_setting);
+
+    flash_sz = boot_setting->bank_0_size;
+
+    // Copy size must be multiple of 256 bytes
+    // else we will got an issue copying current.uf2
+    if (flash_sz & 0xff)
     {
-      result = 256;
-    }else
-    {
-      bootloader_settings_t const * boot_setting;
-      bootloader_util_settings_get(&boot_setting);
-
-      result = boot_setting->bank_0_size;
-
-      // Copy size must be multiple of 256 bytes
-      // else we will got an issue copying current.uf2
-      if (result & 0xff)
-      {
-        result = (result & ~0xff) + 256;
-      }
-
-      // if bank0 size is not valid, happens when flashed with jlink
-      // use maximum application size
-      if ( (result == 0) || (result == 0xFFFFFFFFUL) )
-      {
-        result = FLASH_SIZE;
-      }
+      flash_sz = (flash_sz & ~0xff) + 256;
     }
 
-    flash_sz = result; // presumes atomic 32-bit read/write and static result
+    // if bank0 size is not valid, happens when flashed with jlink
+    // use maximum application size
+    if ( (flash_sz == 0) || (flash_sz == 0xFFFFFFFFUL) )
+    {
+      flash_sz = FLASH_SIZE;
+    }
   }
 
   return flash_sz;
 }
 
+void uf2_init(void)
+{
+  uf2current_flash_sz = current_flash_size();
+}
+
 void padded_memcpy (char *dst, char const *src, int len)
 {
   for ( int i = 0; i < len; ++i )
@@ -282,7 +282,7 @@ void read_block(uint32_t block_no, uint8_t *data) {
                 bl->magicStart1 = UF2_MAGIC_START1;
                 bl->magicEnd = UF2_MAGIC_END;
                 bl->blockNo = sectionIdx;
-                bl->numBlocks = current_flash_size() / 256;
+                bl->numBlocks = uf2current_flash_sz / 256;
                 bl->targetAddr = addr;
                 bl->payloadSize = 256;
                 bl->flags = UF2_FLAG_FAMILYID;
diff --git a/src/usb/uf2/uf2.h b/src/usb/uf2/uf2.h
index eae5054..3b55ba0 100644
--- a/src/usb/uf2/uf2.h
+++ b/src/usb/uf2/uf2.h
@@ -36,12 +36,11 @@ SOFTWARE.
 #include <stdbool.h>
 
 #include "app_util.h"
-
 #include "dfu_types.h"
 
-#define SD_MAGIC_NUMBER 0x51b1e5db
-#define SD_MAGIC_OK() (*((uint32_t*)(SOFTDEVICE_INFO_STRUCT_ADDRESS+4)) == 0x51b1e5db)
-extern bool sdRunning;
+//--------------------------------------------------------------------+
+//
+//--------------------------------------------------------------------+
 
 // All entries are little endian.
 #define UF2_MAGIC_START0  0x0A324655UL // "UF2\n"
@@ -77,77 +76,15 @@ typedef struct {
     uint32_t magicEnd;
 } UF2_Block;
 
-typedef struct {
-    uint8_t version;
-    uint8_t ep_in;
-    uint8_t ep_out;
-    uint8_t reserved0;
-    uint32_t cbw_tag;
-    uint32_t blocks_remaining;
-    uint8_t *buffer;
-} UF2_HandoverArgs;
-
-typedef void (*UF2_MSC_Handover_Handler)(UF2_HandoverArgs *handover);
-typedef void (*UF2_HID_Handover_Handler)(int ep);
-
-// this is required to be exactly 16 bytes long by the linker script
-typedef struct {
-    void *reserved0;
-    UF2_HID_Handover_Handler handoverHID;
-    UF2_MSC_Handover_Handler handoverMSC;
-    const char *info_uf2;
-} UF2_BInfo;
-
-#define UF2_BINFO ((UF2_BInfo *)(APP_START_ADDRESS - sizeof(UF2_BInfo)))
-
-static inline bool is_uf2_block(void *data) {
-    UF2_Block *bl = (UF2_Block *)data;
+static inline bool is_uf2_block(UF2_Block const *bl) {
     return bl->magicStart0 == UF2_MAGIC_START0 && bl->magicStart1 == UF2_MAGIC_START1 &&
            bl->magicEnd == UF2_MAGIC_END;
 }
 
 static inline bool in_uf2_bootloader_space(const void *addr) {
-    return USER_FLASH_END <= (uint32_t)addr && (uint32_t)addr < FLASH_SIZE;
+    return USER_FLASH_END <= (uint32_t)addr /*&& (uint32_t)addr < FLASH_SIZE*/;
 }
 
-
-#ifdef UF2_DEFINE_HANDOVER
-static inline const char *uf2_info(void) {
-    if (in_uf2_bootloader_space(UF2_BINFO->info_uf2))
-        return UF2_BINFO->info_uf2;
-    return "N/A";
-}
-
-static inline void hf2_handover(uint8_t ep) {
-    const char *board_info = UF2_BINFO->info_uf2;
-    UF2_HID_Handover_Handler fn = UF2_BINFO->handoverHID;
-
-    if (in_uf2_bootloader_space(board_info) && in_uf2_bootloader_space((const void *)fn) &&
-        ((uint32_t)fn & 1)) {
-        // Pass control to bootloader; never returns
-        fn(ep & 0xf);
-    }
-}
-
-// the ep_in/ep_out are without the 0x80 mask
-// cbw_tag is in the same bit format as it came
-static inline void check_uf2_handover(uint8_t *buffer, uint32_t blocks_remaining, uint8_t ep_in,
-                                      uint8_t ep_out, uint32_t cbw_tag) {
-    if (!is_uf2_block(buffer))
-        return;
-
-    const char *board_info = UF2_BINFO->info_uf2;
-    UF2_MSC_Handover_Handler fn = UF2_BINFO->handoverMSC;
-
-    if (in_uf2_bootloader_space(board_info) && in_uf2_bootloader_space((const void *)fn) &&
-        ((uint32_t)fn & 1)) {
-        UF2_HandoverArgs hand = {
-            1, ep_in, ep_out, 0, cbw_tag, blocks_remaining, buffer,
-        };
-        // Pass control to bootloader; never returns
-        fn(&hand);
-    }
-}
-#endif
+void uf2_init(void);
 
 #endif
diff --git a/src/usb/uf2/uf2cfg.h b/src/usb/uf2/uf2cfg.h
index ec6dbcc..11de527 100644
--- a/src/usb/uf2/uf2cfg.h
+++ b/src/usb/uf2/uf2cfg.h
@@ -1,15 +1,10 @@
 #include "boards.h"
 
 #define UF2_NUM_BLOCKS     8000   // at least 4,1 MB for FAT16
-
-#ifndef UF2_VOLUME_LABEL
-#define UF2_VOLUME_LABEL   "NRF52BOOT  "
-#endif
-
 #define FLASH_SIZE         (USER_FLASH_END-USER_FLASH_START) // Max flash size
 
 // Only allow to write application TODO dynamic depending on SD size
-#define USER_FLASH_START   0x26000
+#define USER_FLASH_START   (SD_FLASH_SIZE + MBR_SIZE)
 #define USER_FLASH_END     0xAD000 // Fat Fs start here
 
 #define UF2_FAMILY_ID      0xADA52840
diff --git a/src/usb/usb.c b/src/usb/usb.c
index 0115072..c0903ca 100644
--- a/src/usb/usb.c
+++ b/src/usb/usb.c
@@ -34,6 +34,7 @@
 #include "tusb.h"
 #include "usb_desc.h"
 
+#include "uf2/uf2.h"
 #include "boards.h"
 
 //--------------------------------------------------------------------+
@@ -89,6 +90,8 @@ void usb_init(bool cdc_only)
 
   usb_desc_init(cdc_only);
 
+  uf2_init();
+
   // Init TinyUSB stack
   tusb_init();
 }