diff --git a/filesystem/at45db041d.c b/filesystem/at45db041d.c
index 2f3e711..0c6fe37 100644
--- a/filesystem/at45db041d.c
+++ b/filesystem/at45db041d.c
@@ -117,7 +117,8 @@ DRESULT dataflash_random_write(const BYTE *buff, DWORD offset, DWORD length) {
 
     do {
         wait_for_ready();
-        DWORD pageaddr = ((offset/256) << 9) | (offset%256);
+        DWORD pageaddr = (offset/256) << 9;
+        DWORD buffaddr = (offset%256);
         DWORD remaining = 256 - offset%256;
         if (remaining > length) {
             remaining = length;
@@ -137,9 +138,9 @@ DRESULT dataflash_random_write(const BYTE *buff, DWORD offset, DWORD length) {
         // write bytes into the dataflash buffer
         CS_LOW();
         xmit_spi(OP_BUFFER1WRITE);
-        xmit_spi(0x00);
-        xmit_spi(0x00);
-        xmit_spi(0x00);
+        xmit_spi((BYTE)(buffaddr >> 16));
+        xmit_spi((BYTE)(buffaddr >> 8));
+        xmit_spi((BYTE)buffaddr);
         do {
             xmit_spi(*buff++);
         } while (--remaining);
diff --git a/modules/fs.c b/modules/fs.c
index 39cf0a0..fa7a639 100644
--- a/modules/fs.c
+++ b/modules/fs.c
@@ -9,6 +9,8 @@
 #include "filesystem/ff.h"
 #include "filesystem/diskio.h"
 
+#include "usb/usbmsc.h"
+
 #include "core/ssp/ssp.h"
 
 void incBacklight(void);
@@ -44,6 +46,7 @@ const struct MENU_DEF menu_list =   {"FS List",     &fs_list};
 const struct MENU_DEF menu_create = {"FS Create",   &fs_create};
 const struct MENU_DEF menu_format = {"FS format",   &fs_format};
 const struct MENU_DEF menu_read   = {"FS read",     &fs_read};
+const struct MENU_DEF menu_usb   =  {"USB mount",   &usbMSCInit};
 const struct MENU_DEF menu_nop =    {"---",   NULL};
 
 static menuentry menu[] = {
@@ -55,6 +58,8 @@ static menuentry menu[] = {
     &menu_nop,
     &menu_format,
     &menu_nop,
+    &menu_usb,
+    &menu_nop,
     &menu_ISP,
     &menu_incBL,
     &menu_decBL,
diff --git a/usb/usbmsc.c b/usb/usbmsc.c
index 9a34e51..fdb7a4c 100644
--- a/usb/usbmsc.c
+++ b/usb/usbmsc.c
@@ -14,11 +14,11 @@ MSC_DEVICE_INFO MscDevInfo;
 ROM ** rom = (ROM **)0x1fff1ff8;
 
 void usbMSCWrite(uint32_t offset, uint8_t src[], uint32_t length) {
-    dataflash_random_write(src, offset+1, length);
+    dataflash_random_write(src, offset, length);
 }
 
 void usbMSCRead(uint32_t offset, uint8_t dst[], uint32_t length) {
-    dataflash_random_read(dst, offset+1, length);
+    dataflash_random_read(dst, offset, length);
 }
 
 void usbMSCInit(void) {