diff --git a/firmware/deploy.py b/firmware/deploy.py
index 0662eac..e4a4bda 100644
--- a/firmware/deploy.py
+++ b/firmware/deploy.py
@@ -1,19 +1,14 @@
 import struct
-import locale
 from collections import namedtuple
 from datetime import datetime
 import subprocess
 from distutils.version import StrictVersion
-import subprocess
+from esptool import LoadFirmwareImage  # required to get hash and checksum right
 import os
 
-#locale.setlocale(locale.LC_ALL, 'en_US')
+# locale.setlocale(locale.LC_ALL, 'en_US')
 
-# sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t)
-APP_DESC_OFFSET = 32
-
-# sizeof(esp_app_desc_t)
-APP_DESC_SIZE = 256
+APP_DESC_SIZE = 256 # sizeof(esp_app_desc_t)
 
 APP_DESC_STRUCT = "<II2I32s32s16s16s32s32B20I"
 AppDesc = namedtuple('AppDesc',
@@ -28,6 +23,7 @@ AppDesc = namedtuple('AppDesc',
                      ]
                      )
 
+
 def version_number_from_git(tag_prefix='release/', sha_length=10, version_format="{version}.dev{commits}+{sha}"):
     def get_released_versions():
         tags = sorted(subprocess.getoutput('git tag').split('\n'))
@@ -64,24 +60,22 @@ def version_number_from_git(tag_prefix='release/', sha_length=10, version_format
     return version_string
 
 
-def read_app_description(file_name):
+def read_app_description_from_segment(segment):
     def process_bytes(b):
         if not isinstance(b, bytes):
             return b
         s = b.decode()
         return s[:s.find("\x00")]
 
-    with open(file_name, 'rb') as f:
-        f.seek(APP_DESC_OFFSET, 0)
-        raw_app_desc = f.read(APP_DESC_SIZE)
-        unpacked = struct.unpack(APP_DESC_STRUCT, raw_app_desc)
-        unpacked = tuple(process_bytes(e) for e in unpacked)
-        magic_word, secure_version, _, _, version, project_name, time, date, idf_ver, app_elf_sha256, *_ = unpacked
-        assert magic_word == 0xABCD5432
-        return AppDesc(secure_version, version, project_name, time, date, idf_ver, app_elf_sha256)
+    unpacked = struct.unpack(APP_DESC_STRUCT, segment.data[:APP_DESC_SIZE])
+    unpacked = tuple(process_bytes(e) for e in unpacked)
+    magic_word, secure_version, _, _, version, project_name, time, date, idf_ver, app_elf_sha256, *_ = unpacked
+    assert magic_word == 0xABCD5432
+    return AppDesc(secure_version, version, project_name, time, date, idf_ver, app_elf_sha256)
 
 
-def patch_app_description(file_name, version, project_name, time, date):
+
+def patch_app_description_in_segment(segment, version, project_name, time, date):
     assert len(version) < 32
     assert len(project_name) < 32
     assert len(time) < 16
@@ -93,39 +87,41 @@ def patch_app_description(file_name, version, project_name, time, date):
         assert len(s) == total_length
         return s
 
-    with open(file_name, 'r+b') as f:
-        f.seek(APP_DESC_OFFSET, 0)
-        raw_app_desc = f.read(APP_DESC_SIZE)
-        unpacked = list(struct.unpack(APP_DESC_STRUCT, raw_app_desc))
-        unpacked[4] = fill_zeros(version, 32)
-        unpacked[5] = fill_zeros(project_name, 32)
-        unpacked[6] = fill_zeros(time, 16)
-        unpacked[7] = fill_zeros(date, 16)
-        packed = struct.pack(APP_DESC_STRUCT, *unpacked)
-        f.seek(APP_DESC_OFFSET, 0)
-        f.write(packed)
+    raw_app_desc = segment.data[:APP_DESC_SIZE]
+    unpacked = list(struct.unpack(APP_DESC_STRUCT, raw_app_desc))
+    unpacked[4] = fill_zeros(version, 32)
+    unpacked[5] = fill_zeros(project_name, 32)
+    unpacked[6] = fill_zeros(time, 16)
+    unpacked[7] = fill_zeros(date, 16)
+    packed = struct.pack(APP_DESC_STRUCT, *unpacked)
+
+    original_data = segment.data
+    segment.data = packed + original_data[APP_DESC_SIZE:]
 
 
-def add_info_to_firmware(firmware_file, version):
+def patch_firmware(input_file, output_file):
+    img = LoadFirmwareImage("esp32", input_file)
+    version = version_number_from_git()
+
     now = datetime.now()
-    date = now.strftime("%b %d %Y")
     time = now.strftime("%H:%M:%S")
-    patch_app_description(firmware_file, version=version,
-                          project_name="swimtracker.bauer.tech", time=time, date=date)
+    date = now.strftime("%b %d %Y")
+    patch_app_description_in_segment(img.segments[0], version, "swimtracker.bauer.tech", time, date)
+    img.save(output_file)
 
 
 if __name__ == "__main__":
     firmware_file = ".pio/build/esp32/firmware.bin"
     version_file_name = "VERSION"
 
-    version = version_number_from_git()
-    add_info_to_firmware(firmware_file, version)
-    print(read_app_description(firmware_file))
+    patch_firmware(firmware_file, firmware_file) # patch inplace
+
     with open(version_file_name, "w") as version_file:
-      print(version, file=version_file)
+      print(version_number_from_git(), file=version_file)
+
     subprocess.run(["scp", firmware_file, "root@server:/volumes/swimtracker-update"])
     subprocess.run(["scp", version_file_name, "root@server:/volumes/swimtracker-update"])
 
     os.unlink(firmware_file)
     os.unlink(version_file_name)
-    
\ No newline at end of file
+