diff --git a/src/boards.h b/src/boards.h
index 30ad48d..1290308 100644
--- a/src/boards.h
+++ b/src/boards.h
@@ -118,7 +118,6 @@ bool is_ota(void);
 #define PRINTF                printf
 #define PRINT_LOCATION()      printf("%s: %d:\n", __PRETTY_FUNCTION__, __LINE__)
 #define PRINT_MESS(x)         printf("%s: %d: %s \n"   , __FUNCTION__, __LINE__, (char*)(x))
-#define PRTNT_HEAP()          if (CFG_DEBUG == 3) printf("\n%s: %d: Heap free: %d\n", __FUNCTION__, __LINE__, util_heap_get_free_size())
 #define PRINT_STR(x)          printf("%s: %d: " #x " = %s\n"   , __FUNCTION__, __LINE__, (char*)(x) )
 #define PRINT_INT(x)          printf("%s: %d: " #x " = %ld\n"  , __FUNCTION__, __LINE__, (uint32_t) (x) )
 #define PRINT_HEX(x)          printf("%s: %d: " #x " = 0x%X\n"  , __FUNCTION__, __LINE__, (uint32_t) (x) )
@@ -143,7 +142,6 @@ bool is_ota(void);
 #define PRINTF(...)
 #define PRINT_LOCATION()
 #define PRINT_MESS(x)
-#define PRTNT_HEAP()
 #define PRINT_STR(x)
 #define PRINT_INT(x)
 #define PRINT_HEX(x)
diff --git a/src/usb/uf2/ghostfat.c b/src/usb/uf2/ghostfat.c
index 72cadaf..b6aed2e 100644
--- a/src/usb/uf2/ghostfat.c
+++ b/src/usb/uf2/ghostfat.c
@@ -5,7 +5,6 @@
 #include <string.h>
 
 #include "boards.h"
-#include "tusb.h"
 
 #include "bootloader_settings.h"
 #include "bootloader.h"
@@ -99,8 +98,8 @@ static struct TextFile const info[] = {
 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 NUM_FILES          (ARRAY_SIZE(info))
+#define NUM_DIRENTRIES     (NUM_FILES + 1) // Code adds volume label as first root directory entry
 
 #define UF2_SIZE           (uf2current_flash_sz * 2)
 #define UF2_SECTORS        (UF2_SIZE / 512)
@@ -202,7 +201,7 @@ void padded_memcpy (char *dst, char const *src, int len)
 
 
 /*------------------------------------------------------------------*/
-/* Read
+/* Read CURRENT.UF2
  *------------------------------------------------------------------*/
 void read_block(uint32_t block_no, uint8_t *data) {
     memset(data, 0, 512);
@@ -311,19 +310,17 @@ int write_block(uint32_t block_no, uint8_t *data, WriteState *state) {
         return -1;
     }
 
+    // PRINTF("Addr = 0x%08X, Family = 0x%08X\n", bl->targetAddr, bl->familyID);
+
     // only accept block with same family id
-    if ( !((bl->flags & UF2_FLAG_FAMILYID) && (bl->familyID == CFG_UF2_FAMILY_ID)) ) {
+    if ( !((bl->familyID == CFG_UF2_FAMILY_ID)) ) {
       return -1;
     }
 
-    if ((bl->flags & UF2_FLAG_NOFLASH) || bl->payloadSize > 256 || (bl->targetAddr & 0xff) ||
-        (bl->targetAddr < USER_FLASH_START) || (bl->targetAddr + bl->payloadSize > USER_FLASH_END) ) {
+    if ( (bl->targetAddr < USER_FLASH_START) || (bl->targetAddr + bl->payloadSize > USER_FLASH_END) ) {
 
-        //NRF_LOG_WARNING("Skip block at %x", bl->targetAddr);
-        // this happens when we're trying to re-flash CURRENT.UF2 file previously
-        // copied from a device; we still want to count these blocks to reset properly
     } else {
-        //NRF_LOG_DEBUG("Write block at %x", bl->targetAddr);
+        //PRINTF("Write block at %x", bl->targetAddr);
 
         static bool first_write = true;
         if ( first_write ) {
@@ -354,7 +351,7 @@ int write_block(uint32_t block_no, uint8_t *data, WriteState *state) {
                 flash_nrf5x_flush(true);
             }
         }
-        //NRF_LOG_DEBUG("wr %d=%d (of %d)", state->numWritten, bl->blockNo, bl->numBlocks);
+        //PRINTF("wr %d=%d (of %d)", state->numWritten, bl->blockNo, bl->numBlocks);
     }
 
     return 512;
diff --git a/src/usb/uf2/uf2.h b/src/usb/uf2/uf2.h
index 339b109..17f430a 100644
--- a/src/usb/uf2/uf2.h
+++ b/src/usb/uf2/uf2.h
@@ -78,7 +78,9 @@ typedef struct {
 
 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);
+           (bl->magicEnd == UF2_MAGIC_END) &&
+           (bl->flags & UF2_FLAG_FAMILYID) && !(bl->flags & UF2_FLAG_NOFLASH) &&
+           (bl->payloadSize == 256) && !(bl->targetAddr & 0xff);
 }
 
 static inline bool in_uf2_bootloader_space(const void *addr) {
diff --git a/src/usb/uf2/uf2cfg.h b/src/usb/uf2/uf2cfg.h
index 9c8406a..27ebbaf 100644
--- a/src/usb/uf2/uf2cfg.h
+++ b/src/usb/uf2/uf2cfg.h
@@ -1,10 +1,11 @@
 #include "boards.h"
 
-#define UF2_NUM_BLOCKS     8000   // at least 4,1 MB for FAT16
-#define FLASH_SIZE         (USER_FLASH_END-USER_FLASH_START) // Max flash size
+#define UF2_NUM_BLOCKS        8000   // at least 4,1 MB for FAT16
+#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   (SD_FLASH_SIZE + MBR_SIZE)
-#define USER_FLASH_END     0xAD000 // Fat Fs start here
+#define USER_FLASH_START      (SD_FLASH_SIZE + MBR_SIZE)
+#define USER_FLASH_END        0xAD000 // Fat Fs start here
 
-#define CFG_UF2_FAMILY_ID  0xADA52840
+#define CFG_UF2_FAMILY_ID     0xADA52840
+#define CFG_UF2_BOOTLOADER_ID ((USB_DESC_VID << 16) | USB_DESC_UF2_PID)