diff --git a/components/fatfs/fatfs_utils/long_filename_utils.py b/components/fatfs/fatfs_utils/long_filename_utils.py
index 0e1521c612..649312aead 100644
--- a/components/fatfs/fatfs_utils/long_filename_utils.py
+++ b/components/fatfs/fatfs_utils/long_filename_utils.py
@@ -3,6 +3,7 @@
 from typing import List
 
 from .entry import Entry
+from .exceptions import NoFreeClusterException
 from .utils import build_name, convert_to_utf16_and_pad
 
 #  File name with long filenames support can be as long as memory allows. It is split into entries
@@ -11,6 +12,8 @@ from .utils import build_name, convert_to_utf16_and_pad
 #  For creating long name entries we need to split the name by 13 characters using `split_name_to_lfn_entries`
 #  and in every entry into three blocks with sizes 5, 6 and 2 characters using `split_name_to_lfn_entry`.
 
+MAXIMAL_FILES_SAME_PREFIX: int = 127
+
 
 def get_required_lfn_entries_count(lfn_full_name: str) -> int:
     """
@@ -68,16 +71,18 @@ def build_lfn_unique_entry_name_order(entities: list, lfn_entry_name: str) -> in
     The short entry contains only the first 6 characters of the file name,
     and we have to distinguish it from other names within the directory starting with the same 6 characters.
     To make it unique, we add its order in relation to other names such that lfn_entry_name[:6] == other[:6].
-    The order is specified by the character, starting with '1'.
+    The order is specified by the character, starting with chr(1).
 
     E.g. the file in directory 'thisisverylongfilenama.txt' will be named 'THISIS~1TXT' in its short entry.
     If we add another file 'thisisverylongfilenamax.txt' its name in the short entry will be 'THISIS~2TXT'.
     """
-    preceding_entries: int = 0
+    preceding_entries: int = 1
     for entity in entities:
         if entity.name[:6] == lfn_entry_name[:6]:
             preceding_entries += 1
-    return preceding_entries + ord('1')
+    if preceding_entries > MAXIMAL_FILES_SAME_PREFIX:
+        raise NoFreeClusterException('Maximal number of files with the same prefix is 127')
+    return preceding_entries
 
 
 def build_lfn_full_name(name: str, extension: str) -> str:
diff --git a/components/fatfs/test_fatfsgen/test_fatfsgen.py b/components/fatfs/test_fatfsgen/test_fatfsgen.py
index 1f7d3b2983..7d1f702390 100755
--- a/components/fatfs/test_fatfsgen/test_fatfsgen.py
+++ b/components/fatfs/test_fatfsgen/test_fatfsgen.py
@@ -311,11 +311,11 @@ class FatFSGen(unittest.TestCase):
         fatfs.create_file('HELLOHELLOHELLO', extension='TXT')
         fatfs.write_filesystem(CFG['output_file'])
         file_system = read_filesystem(CFG['output_file'])
-        self.assertEqual(file_system[0x2000: 0x2010], b'Bl\x00o\x00.\x00t\x00x\x00\x0f\x00\xb3t\x00')
+        self.assertEqual(file_system[0x2000: 0x2010], b'Bl\x00o\x00.\x00t\x00x\x00\x0f\x00\xadt\x00')
         self.assertEqual(file_system[0x2012: 0x2020], b'\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
-        self.assertEqual(file_system[0x2020: 0x2030], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\xb3h\x00')
+        self.assertEqual(file_system[0x2020: 0x2030], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\xadh\x00')
         self.assertEqual(file_system[0x2030: 0x2040], b'e\x00l\x00l\x00o\x00h\x00\x00\x00e\x00l\x00')
-        self.assertEqual(file_system[0x2040: 0x2050], b'HELLOH~1TXT \x00\x00\x00\x00')
+        self.assertEqual(file_system[0x2040: 0x2050], b'HELLOH~\x01TXT \x00\x00\x00\x00')
         self.assertEqual(file_system[0x2050: 0x2060], b'!\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x00\x00\x00\x00')
 
     def test_lfn_plain_name(self) -> None:
@@ -324,11 +324,11 @@ class FatFSGen(unittest.TestCase):
         fatfs.write_content(path_from_root=['HELLOHELLOHELLO.TXT'], content=b'this is a test')
         fatfs.write_filesystem(CFG['output_file'])
         file_system = read_filesystem(CFG['output_file'])
-        self.assertEqual(file_system[0x2000: 0x2010], b'Bl\x00o\x00.\x00t\x00x\x00\x0f\x00\xb3t\x00')
+        self.assertEqual(file_system[0x2000: 0x2010], b'Bl\x00o\x00.\x00t\x00x\x00\x0f\x00\xadt\x00')
         self.assertEqual(file_system[0x2012: 0x2020], b'\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
-        self.assertEqual(file_system[0x2020: 0x2030], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\xb3h\x00')
+        self.assertEqual(file_system[0x2020: 0x2030], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\xadh\x00')
         self.assertEqual(file_system[0x2030: 0x2040], b'e\x00l\x00l\x00o\x00h\x00\x00\x00e\x00l\x00')
-        self.assertEqual(file_system[0x2040: 0x2050], b'HELLOH~1TXT \x00\x00\x00\x00')
+        self.assertEqual(file_system[0x2040: 0x2050], b'HELLOH~\x01TXT \x00\x00\x00\x00')
         self.assertEqual(file_system[0x2050: 0x2060], b'!\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x0e\x00\x00\x00')
         self.assertEqual(file_system[0x6000: 0x6010], b'this is a test\x00\x00')
 
@@ -338,11 +338,11 @@ class FatFSGen(unittest.TestCase):
         fatfs.write_content(path_from_root=['HELLOHELLOHELLO'], content=b'this is a test')
         fatfs.write_filesystem(CFG['output_file'])
         file_system = read_filesystem(CFG['output_file'])
-        self.assertEqual(file_system[0x2000: 0x2010], b'Bl\x00o\x00\x00\x00\xff\xff\xff\xff\x0f\x00V\xff\xff')
+        self.assertEqual(file_system[0x2000: 0x2010], b'Bl\x00o\x00\x00\x00\xff\xff\xff\xff\x0f\x00P\xff\xff')
         self.assertEqual(file_system[0x2012: 0x2020], b'\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
-        self.assertEqual(file_system[0x2020: 0x2030], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00Vh\x00')
+        self.assertEqual(file_system[0x2020: 0x2030], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00Ph\x00')
         self.assertEqual(file_system[0x2030: 0x2040], b'e\x00l\x00l\x00o\x00h\x00\x00\x00e\x00l\x00')
-        self.assertEqual(file_system[0x2040: 0x2050], b'HELLOH~1    \x00\x00\x00\x00')
+        self.assertEqual(file_system[0x2040: 0x2050], b'HELLOH~\x01    \x00\x00\x00\x00')
         self.assertEqual(file_system[0x2050: 0x2060], b'!\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x0e\x00\x00\x00')
         self.assertEqual(file_system[0x6000: 0x6010], b'this is a test\x00\x00')
 
@@ -356,11 +356,11 @@ class FatFSGen(unittest.TestCase):
         fatfs.create_file('HELLO', extension='TXT', path_from_root=['VERYLONGTESTFOLD'])
         fatfs.write_filesystem(CFG['output_file'])
         file_system = read_filesystem(CFG['output_file'])
-        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\xa6\xff\xff')
+        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\xa0\xff\xff')
         self.assertEqual(file_system[0x2012: 0x2020], b'\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
-        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\xa6o\x00')
+        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\xa0o\x00')
         self.assertEqual(file_system[0x2030: 0x2040], b'n\x00g\x00t\x00e\x00s\x00\x00\x00t\x00f\x00')
-        self.assertEqual(file_system[0x2040: 0x2050], b'VERYLO~1   \x10\x00\x00\x00\x00')
+        self.assertEqual(file_system[0x2040: 0x2050], b'VERYLO~\x01   \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x2050: 0x2060], b'!\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x00\x00\x00\x00')
 
         self.assertEqual(file_system[0x6000: 0x6010], b'.          \x10\x00\x00\x00\x00')
@@ -377,18 +377,18 @@ class FatFSGen(unittest.TestCase):
         fatfs.write_filesystem(CFG['output_file'])
 
         file_system = read_filesystem(CFG['output_file'])
-        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\x10\xff\xff')
+        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\n\xff\xff')
         self.assertEqual(file_system[0x2012: 0x2020], b'\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
-        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\x10o\x00')
+        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\no\x00')
         self.assertEqual(file_system[0x2030: 0x2040], b'n\x00g\x00t\x00e\x00s\x00\x00\x00t\x00f\x00')
-        self.assertEqual(file_system[0x2040: 0x2050], b'verylo~1   \x10\x00\x00\x00\x00')
+        self.assertEqual(file_system[0x2040: 0x2050], b'verylo~\x01   \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x2050: 0x2060], b'!\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x00\x00\x00\x00')
 
         self.assertEqual(file_system[0x6000: 0x6010], b'.          \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x6012: 0x6020], b'!\x00\x00\x00\x00\x00!\x00\x02\x00\x00\x00\x00\x00')
         self.assertEqual(file_system[0x6020: 0x6030], b'..         \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x6030: 0x6040], b'!\x00!\x00\x00\x00\x00\x00!\x00\x01\x00\x00\x00\x00\x00')
-        self.assertEqual(file_system[0x6040: 0x6050], b'Bl\x00o\x00.\x00t\x00x\x00\x0f\x00\xd5t\x00')
+        self.assertEqual(file_system[0x6040: 0x6050], b'Bl\x00o\x00.\x00t\x00x\x00\x0f\x00\xcft\x00')
         self.assertEqual(file_system[0x6050: 0x6060],
                          b'\x00\x00\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
 
@@ -399,11 +399,11 @@ class FatFSGen(unittest.TestCase):
         fatfs.write_content(path_from_root=['VERYLONGTESTFOLD', 'HELLO.TXT'], content=b'this is a test')
         fatfs.write_filesystem(CFG['output_file'])
         file_system = read_filesystem(CFG['output_file'])
-        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\xa6\xff\xff')
+        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\xa0\xff\xff')
         self.assertEqual(file_system[0x2012: 0x2020], b'\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
-        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\xa6o\x00')
+        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\xa0o\x00')
         self.assertEqual(file_system[0x2030: 0x2040], b'n\x00g\x00t\x00e\x00s\x00\x00\x00t\x00f\x00')
-        self.assertEqual(file_system[0x2040: 0x2050], b'VERYLO~1   \x10\x00\x00\x00\x00')
+        self.assertEqual(file_system[0x2040: 0x2050], b'VERYLO~\x01   \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x2050: 0x2060], b'!\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x00\x00\x00\x00')
 
         self.assertEqual(file_system[0x6000: 0x6010], b'.          \x10\x00\x00\x00\x00')
@@ -447,31 +447,31 @@ class FatFSGen(unittest.TestCase):
         fatfs.write_filesystem(CFG['output_file'])
         file_system = read_filesystem(CFG['output_file'])
 
-        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\xa6\xff\xff')
+        self.assertEqual(file_system[0x2000: 0x2010], b'Bo\x00l\x00d\x00\x00\x00\xff\xff\x0f\x00\xa0\xff\xff')
         self.assertEqual(file_system[0x2011: 0x2020], b'\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00\x00\xff\xff\xff\xff')
-        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\xa6o\x00')
+        self.assertEqual(file_system[0x2020: 0x2030], b'\x01v\x00e\x00r\x00y\x00l\x00\x0f\x00\xa0o\x00')
         self.assertEqual(file_system[0x2030: 0x2040], b'n\x00g\x00t\x00e\x00s\x00\x00\x00t\x00f\x00')
-        self.assertEqual(file_system[0x2040: 0x2050], b'VERYLO~1   \x10\x00\x00\x00\x00')
+        self.assertEqual(file_system[0x2040: 0x2050], b'VERYLO~\x01   \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x2050: 0x2060], b'!\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x00\x00\x00\x00')
 
         self.assertEqual(file_system[0x6000: 0x6010], b'.          \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x6011: 0x6020], b'\x00!\x00\x00\x00\x00\x00!\x00\x02\x00\x00\x00\x00\x00')
         self.assertEqual(file_system[0x6020: 0x6030], b'..         \x10\x00\x00\x00\x00')
         self.assertEqual(file_system[0x6030: 0x6040], b'!\x00!\x00\x00\x00\x00\x00!\x00\x01\x00\x00\x00\x00\x00')
-        self.assertEqual(file_system[0x6040: 0x6050], b'Bl\x00o\x00o\x00o\x00o\x00\x0f\x00\xb3o\x00')
+        self.assertEqual(file_system[0x6040: 0x6050], b'Bl\x00o\x00o\x00o\x00o\x00\x0f\x00\xado\x00')
         self.assertEqual(file_system[0x6050: 0x6060], b'o\x00o\x00.\x00t\x00x\x00\x00\x00t\x00\x00\x00')
 
         self.assertEqual(file_system[0x6050: 0x6060], b'o\x00o\x00.\x00t\x00x\x00\x00\x00t\x00\x00\x00')
-        self.assertEqual(file_system[0x6060: 0x6070], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\xb3h\x00')
+        self.assertEqual(file_system[0x6060: 0x6070], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\xadh\x00')
         self.assertEqual(file_system[0x6070: 0x6080], b'e\x00l\x00l\x00o\x00h\x00\x00\x00e\x00l\x00')
-        self.assertEqual(file_system[0x6080: 0x6090], b'HELLOH~1TXT \x00\x00\x00\x00')
+        self.assertEqual(file_system[0x6080: 0x6090], b'HELLOH~\x01TXT \x00\x00\x00\x00')
         self.assertEqual(file_system[0x6090: 0x60a0], b'!\x00!\x00\x00\x00\x00\x00!\x00\x03\x00\x10\x00\x00\x00')
-        self.assertEqual(file_system[0x60a0: 0x60b0], b'Bl\x00o\x00o\x00o\x00o\x00\x0f\x00\x93o\x00')
+        self.assertEqual(file_system[0x60a0: 0x60b0], b'Bl\x00o\x00o\x00o\x00o\x00\x0f\x00\x8do\x00')
 
         self.assertEqual(file_system[0x60b0: 0x60c0], b'o\x00b\x00.\x00t\x00x\x00\x00\x00t\x00\x00\x00')
-        self.assertEqual(file_system[0x60c0: 0x60d0], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\x93h\x00')
+        self.assertEqual(file_system[0x60c0: 0x60d0], b'\x01h\x00e\x00l\x00l\x00o\x00\x0f\x00\x8dh\x00')
         self.assertEqual(file_system[0x60d0: 0x60e0], b'e\x00l\x00l\x00o\x00h\x00\x00\x00e\x00l\x00')
-        self.assertEqual(file_system[0x60e0: 0x60f0], b'HELLOH~2TXT \x00\x00\x00\x00')
+        self.assertEqual(file_system[0x60e0: 0x60f0], b'HELLOH~\x02TXT \x00\x00\x00\x00')
 
 
 if __name__ == '__main__':