diff --git a/README.md b/README.md
index 938e431..e986f92 100644
--- a/README.md
+++ b/README.md
@@ -1,12 +1,16 @@
 # python-validity
-Validity fingerprint sensor library.
-Originally designed to capture some of my findings for 138a:0097, but if you manage to get it working for some other Validity sensor - pull requests are welcome.
+Validity fingerprint sensor driver.
 
 ## Setting up
 
-On a Debian-based system, to re-install from sources (useful for testing):
+On Ubuntu system:
 ```
-./setup.py install --force --install-layout deb --prefix=/usr --root=/
+$ sudo apt remove fprintd
+$ sudo add-apt-repository ppa:uunicorn/open-fprintd
+$ sudo aptget update
+$ sudo apt install open-fprintd fprintd-clients python-validity
+...wait a bit...
+$ fprintd-enroll
 ```
 
 ## Initialization
diff --git a/bin/validity-sensors-firmware b/bin/validity-sensors-firmware
new file mode 100755
index 0000000..998017f
--- /dev/null
+++ b/bin/validity-sensors-firmware
@@ -0,0 +1,122 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+#
+# 2020 - Marco Trevisan
+#
+# Initializer for ThinkPad's validity sensors 138a:0090 and 138a:0097 and 06cb:009a
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import argparse
+import os
+import subprocess
+import sys
+import tempfile
+import urllib.request
+import shutil
+
+from enum import Enum, auto
+from time import sleep
+from usb import core as usb_core
+
+python_validity_data='/usr/share/python-validity/'
+
+# FIXME: supported usb ids are duplicated in usb.py
+class VFS(Enum):
+    DEV_90 = (0x138a, 0x0090)
+    DEV_97 = (0x138a, 0x0097)
+    DEV_9a = (0x06cb, 0x009a)
+
+DEFAULT_URIS = {
+    VFS.DEV_90: {
+        'driver': 'https://download.lenovo.com/pccbbs/mobiles/n1cgn08w.exe',
+        'referral': 'https://support.lenovo.com/us/en/downloads/DS120491',
+    },
+    VFS.DEV_97: {
+        'driver': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe',
+        'referral': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe'
+    },
+    VFS.DEV_9a: {
+        'driver': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe',
+        'referral': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe'
+    }
+}
+
+# FIXME: filenames are duplicated in upload_fwext.py
+DEFAULT_FW_NAMES = {
+    VFS.DEV_90: '6_07f_Lenovo.xpfwext',
+    VFS.DEV_97: '6_07f_lenovo_mis_qm.xpfwext',
+    VFS.DEV_9a: '6_07f_lenovo_mis_qm.xpfwext'
+}
+
+
+def download_and_extract_fw(dev_type, fwdir, fwuri=None):
+    fwuri = fwuri if fwuri else DEFAULT_URIS[dev_type]['driver']
+    fwarchive = os.path.join(fwdir, 'fwinstaller.exe')
+    fwname = DEFAULT_FW_NAMES[dev_type]
+
+    print('Downloading {} to extract {}'.format(fwuri, fwname))
+
+    req = urllib.request.Request(fwuri)
+    req.add_header('Referer', DEFAULT_URIS[dev_type].get('referral', ''))
+    req.add_header('User-Agent', 'Mozilla/5.0 (X11; U; Linux)')
+
+    with urllib.request.urlopen(req) as response:
+        with open(fwarchive, 'wb') as out_file:
+            out_file.write(response.read())
+
+    subprocess.check_call(['innoextract',
+        '--output-dir', fwdir,
+        '--include', fwname,
+        '--collisions', 'overwrite',
+        fwarchive
+    ])
+
+    fwpath = subprocess.check_output([
+        'find', fwdir, '-name', fwname]).decode('utf-8').strip()
+    print('Found firmware at {}'.format(fwpath))
+
+    if not fwpath:
+        raise Exception('No {} found in the archive'.format(fwname))
+
+    return fwpath
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--driver-uri')
+
+    args = parser.parse_args()
+
+    if os.geteuid() != 0:
+        raise Exception('This script needs to be executed as root')
+
+    dev_type = None
+    for d in VFS:
+        dev = usb_core.find(idVendor=d.value[0], idProduct=d.value[1])
+        if dev:
+            dev_type = d
+
+    if not dev_type:
+        raise Exception('No supported validity device found')
+
+    try:
+        subprocess.check_call(['innoextract', '--version'],
+            stdout=subprocess.DEVNULL)
+    except Exception as e:
+        print('Impossible to run innoextract: {}'.format(e))
+        sys.exit(1)
+
+    with tempfile.TemporaryDirectory() as fwdir:
+        fwpath = download_and_extract_fw(dev_type, fwdir, fwuri=args.driver_uri)
+        shutil.copy(fwpath, python_validity_data)
diff --git a/bin/validity-sensors-initializer b/bin/validity-sensors-initializer
deleted file mode 100755
index c588318..0000000
--- a/bin/validity-sensors-initializer
+++ /dev/null
@@ -1,239 +0,0 @@
-#!/usr/bin/env python3
-# -*- coding: utf-8 -*-
-#
-# 2020 - Marco Trevisan
-#
-# Initializer for ThinkPad's validity sensors 138a:0090 and 138a:0097 and 06cb:009a
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-import argparse
-import os
-import subprocess
-import sys
-import tempfile
-import urllib.request
-import shutil
-
-
-from enum import Enum, auto
-from time import sleep
-from usb import core as usb_core
-
-from validitysensor.flash import read_tls_flash
-from validitysensor.init_db import init_db
-from validitysensor.init_flash import init_flash
-from validitysensor.sensor import sensor as vfs_sensor
-from validitysensor.sensor import factory_reset
-from validitysensor.tls import tls as vfs_tls
-from validitysensor.upload_fwext import upload_fwext
-from validitysensor.usb import usb as vfs_usb
-
-class VFS(Enum):
-    DEV_90 = (0x138a, 0x0090)
-    DEV_97 = (0x138a, 0x0097)
-    DEV_9a = (0x06cb, 0x009a)
-
-DEFAULT_URIS = {
-    VFS.DEV_90: {
-        'driver': 'https://download.lenovo.com/pccbbs/mobiles/n1cgn08w.exe',
-        'referral': 'https://support.lenovo.com/us/en/downloads/DS120491',
-    },
-    VFS.DEV_97: {
-        'driver': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe',
-        'referral': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe'
-    },
-    VFS.DEV_9a: {
-        'driver': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe',
-        'referral': 'https://download.lenovo.com/pccbbs/mobiles/nz3gf07w.exe'
-    }
-}
-
-DEFAULT_FW_NAMES = {
-    VFS.DEV_90: '6_07f_Lenovo.xpfwext',
-    VFS.DEV_97: '6_07f_lenovo_mis_qm.xpfwext',
-    VFS.DEV_9a: '6_07f_lenovo_mis_qm.xpfwext'
-}
-
-
-class VFSInitializer():
-    def __init__(self, args, usb_dev, dev_type):
-        self.args = args
-        self.usb_dev = usb_dev
-        self.dev_type = dev_type
-        self.dev_str = repr(usb_dev)
-
-        print('Found device {}'.format(self.dev_str))
-
-        if self.args.host_product or self.args.host_serial:
-            vfs_tls.set_hwkey(product_name=self.args.host_product,
-                serial_number=self.args.host_serial)
-
-    def open_device(self, init=False):
-        print('Opening device',hex(self.dev_type.value[1]))
-        vfs_usb.open(vendor=self.dev_type.value[0], product=self.dev_type.value[1])
-
-        if init:
-            vfs_usb.send_init()
-
-            # try to init TLS session from the flash
-            vfs_tls.parseTlsFlash(read_tls_flash())
-            vfs_tls.open()
-
-    def restart(self):
-        vfs_tls.reset()
-        self.open_device(init=True)
-
-    def download_and_extract_fw(self, fwdir, fwuri=None):
-        fwuri = fwuri if fwuri else DEFAULT_URIS[self.dev_type]['driver']
-        fwarchive = os.path.join(fwdir, 'fwinstaller.exe')
-        fwname = DEFAULT_FW_NAMES[self.dev_type]
-
-        print('Downloading {} to extract {}'.format(fwuri, fwname))
-
-        req = urllib.request.Request(fwuri)
-        req.add_header('Referer', DEFAULT_URIS[self.dev_type].get('referral', ''))
-        req.add_header('User-Agent', 'Mozilla/5.0 (X11; U; Linux)')
-
-        with urllib.request.urlopen(req) as response:
-            with open(fwarchive, 'wb') as out_file:
-                out_file.write(response.read())
-
-        subprocess.check_call(['innoextract',
-            '--output-dir', fwdir,
-            '--include', fwname,
-            '--collisions', 'overwrite',
-            fwarchive
-        ])
-
-        fwpath = subprocess.check_output([
-            'find', fwdir, '-name', fwname]).decode('utf-8').strip()
-        print('Found firmware at {}'.format(fwpath))
-
-        if not fwpath:
-            raise Exception('No {} found in the archive'.format(fwname))
-
-        return fwpath
-
-    def sleep(self, sec=3):
-        print('Sleeping...')
-        sleep(sec)
-
-    def try_factory_reset(self):
-        self.open_device()
-        try:
-            print('Factory reset...')
-            factory_reset()
-        except Exception as e:
-            print('Factory reset failed with {}, this should not happen, but ' \
-                    'we can ignore it, if pairing works...'.format(e))
-
-    def pair(self):
-        print('Pairing the sensor with device')
-
-        max_retries = 5
-        err = None
-        for i in range(0, max_retries):
-            try:
-                self.open_device()
-
-                print('Initializing flash...')
-                init_flash()
-                break
-            except Exception as e:
-                if err is None:
-                    err = e
-                self.sleep()
-                print('Try {} failed with error: {}'.format(i+1, e))
-            finally:
-                max_retries -= 1
-
-            if max_retries == 0:
-                print('Device didn\'t show up after reset, retry...')
-                raise(err)
-
-        self.sleep()
-        self.restart()
-
-        print('Uploading firmware...')
-        upload_fwext()
-
-        self.sleep()
-        self.restart()
-
-        print('Calibrating...')
-        vfs_sensor.open()
-        vfs_sensor.calibrate()
-
-        print('Init database...')
-        init_db()
-
-        vfs_tls.reset()
-
-        print('That\'s it, pairing with {} finished'.format(self.dev_str))
-
-
-if __name__ == "__main__":
-    parser = argparse.ArgumentParser()
-    parser.add_argument('--driver-uri')
-    parser.add_argument('--firmware-path', type=argparse.FileType('r'))
-    parser.add_argument('--calibration-data', type=argparse.FileType('r'))
-    parser.add_argument('--host-product')
-    parser.add_argument('--host-serial')
-    parser.add_argument('--simulate-virtualbox', action='store_true')
-    parser.add_argument('--download-fw-only', action='store_true')
-
-    args = parser.parse_args()
-
-    if args.simulate_virtualbox and (args.host_product or args.host_serial):
-        parser.error("--simulate-virtualbox is incompatible with host params.")
-
-    if os.geteuid() != 0:
-        raise Exception('This script needs to be executed as root')
-
-    usb_dev = None
-    for d in VFS:
-        dev = usb_core.find(idVendor=d.value[0], idProduct=d.value[1])
-        if dev:
-            dev_type = d
-            usb_dev = dev
-
-    if not usb_dev:
-        raise Exception('No supported validity device found')
-
-    try:
-        subprocess.check_call(['innoextract', '--version'],
-            stdout=subprocess.DEVNULL)
-    except Exception as e:
-        print('Impossible to run innoextract: {}'.format(e))
-        sys.exit(1)
-
-    vfs_initializer = VFSInitializer(args, usb_dev, dev_type)
-
-    with tempfile.TemporaryDirectory() as fwdir:
-        if args.firmware_path:
-            fwpath = args.firmware_path.name
-        else:
-            fwpath = vfs_initializer.download_and_extract_fw(fwdir,
-                fwuri=args.driver_uri)
-
-        shutil.copy(fwpath, '/usr/share/python-validity/')
-
-        if not args.download_fw_only:
-            input('The device will be now reset to factory and associated to the ' \
-                    'current laptop.\nPress Enter to continue (or Ctrl+C to cancel)...')
-
-            vfs_initializer.try_factory_reset()
-            vfs_initializer.sleep()
-            vfs_initializer.pair()
diff --git a/dbus_service/dbus-service b/dbus_service/dbus-service
index 62ca9df..3c22625 100755
--- a/dbus_service/dbus-service
+++ b/dbus_service/dbus-service
@@ -2,6 +2,7 @@
 
 import argparse
 import re
+import sys
 import dbus
 import dbus.mainloop.glib
 import dbus.service
@@ -15,7 +16,7 @@ from validitysensor.tls import tls
 from validitysensor.usb import usb
 from validitysensor.sid import sid_from_string
 from validitysensor.db import subtype_to_string, db
-from validitysensor.sensor import sensor, reboot
+from validitysensor.sensor import sensor, reboot, RebootException
 import pwd
 
 GLib.threads_init()
@@ -166,14 +167,18 @@ if __name__ == '__main__':
         usb.trace_enabled = True
         tls.trace_enabled = True
 
-    if args.devpath is None:
-        init.open()
-    else:
-        z = re.match('^usb-(\d+)-(\d+)$', args.devpath)
-        if not z:
-            parser.error('Option --devpath should look like this: usb-<busnum>-<address>')
+    try:
+        if args.devpath is None:
+            init.open()
+        else:
+            z = re.match('^usb-(\d+)-(\d+)$', args.devpath)
+            if not z:
+                parser.error('Option --devpath should look like this: usb-<busnum>-<address>')
 
-        init.open_devpath(*map(int, z.groups()))
+            init.open_devpath(*map(int, z.groups()))
+    except RebootException:
+        print('Initialization ended up in rebooting the sensor. Normal exit.')
+        sys.exit(0)
 
     bus = dbus.SystemBus()
 
diff --git a/debian/python3-validity.postinst b/debian/python3-validity.postinst
index 0a27942..ca62874 100644
--- a/debian/python3-validity.postinst
+++ b/debian/python3-validity.postinst
@@ -4,6 +4,7 @@ set -e
 #DEBHELPER#
 
 if [ "$1" = "configure" ]; then
+    validity-sensors-firmware || true
     systemctl daemon-reload || true
     udevadm control --reload-rules || true
     udevadm trigger || true
diff --git a/debian/python3-validity@.service b/debian/python3-validity@.service
index 03bf2fd..d69c127 100644
--- a/debian/python3-validity@.service
+++ b/debian/python3-validity@.service
@@ -5,5 +5,6 @@ Description=python-validity driver dbus service for %I
 [Service]
 Type=simple
 ExecStart=/usr/lib/python-validity/dbus-service --devpath %i
+StandardOutput=syslog
 Restart=no
 
diff --git a/scripts/factory-reset.py b/scripts/factory-reset.py
index 8589616..a997d50 100644
--- a/scripts/factory-reset.py
+++ b/scripts/factory-reset.py
@@ -1,6 +1,9 @@
 
 from validitysensor.usb import usb
-from validitysensor.sensor import factory_reset
+from validitysensor.sensor import factory_reset, RebootException
 
-usb.open()
-factory_reset()
+try:
+    usb.open()
+    factory_reset()
+except RebootException:
+    pass
diff --git a/scripts/pair.py b/scripts/pair.py
deleted file mode 100644
index a16d694..0000000
--- a/scripts/pair.py
+++ /dev/null
@@ -1,44 +0,0 @@
-
-from time import sleep
-
-from validitysensor.usb import usb
-from validitysensor.tls import tls
-from validitysensor.flash import read_tls_flash
-from validitysensor.init_flash import init_flash
-from validitysensor.upload_fwext import upload_fwext
-from validitysensor.init_db import init_db
-from validitysensor.sensor import sensor, reboot
-
-#usb.trace_enabled=True
-#tls.trace_enabled=True
-
-def restart():
-    print('Sleeping...')
-    sleep(3)
-    tls.reset()
-    usb.open()
-    usb.send_init()
-    tls.parseTlsFlash(read_tls_flash())
-    tls.open()
-
-try:
-    usb.open()
-    print('Initializing flash...')
-    init_flash()
-
-    restart()
-    print('Uploading firmware...')
-    upload_fwext()
-
-    restart()
-    print('Calibrating...')
-    sensor.open(False)
-    sensor.calibrate()
-
-    print('Init database...')
-    init_db()
-
-    print('That\'s it, pairing\'s finished')
-finally:
-    sleep(1)
-    reboot()
diff --git a/setup.py b/setup.py
index 9309715..64bab60 100755
--- a/setup.py
+++ b/setup.py
@@ -8,7 +8,7 @@ setup(name='python-validity',
     packages=['validitysensor'],
     scripts=[
         'bin/validity-led-dance',
-        'bin/validity-sensors-initializer',
+        'bin/validity-sensors-firmware',
     ],
     install_requires=[
         'cryptography >= 2.1.4',
@@ -21,7 +21,6 @@ setup(name='python-validity',
             'scripts/dbus-cmd.py', 
             'scripts/lsdbus.py', 
             'scripts/factory-reset.py', 
-            'scripts/pair.py', 
             'scripts/prototype.py'
         ]),
     ]
diff --git a/validitysensor/flash.py b/validitysensor/flash.py
index 984efd8..ce4dad8 100644
--- a/validitysensor/flash.py
+++ b/validitysensor/flash.py
@@ -121,10 +121,10 @@ def write_flash_all(partition, ptr, buf):
         write_flash(partition, ptr, chunk)
         ptr += len(chunk)
 
-def read_flash_all(partition, start, end):
+def read_flash_all(partition, start, size):
     bs = 0x1000
-    blocks = [read_flash(partition, addr, bs) for addr in range(start, end, bs)]
-    return b''.join(blocks)
+    blocks = [read_flash(partition, addr, bs) for addr in range(start, start+size, bs)]
+    return b''.join(blocks)[:size]
 
 def write_fw_signature(partition, signature):
     rsp=tls.cmd(pack('<BBxH', 0x42, partition, len(signature)) + signature)
diff --git a/validitysensor/init.py b/validitysensor/init.py
index 65cb1dc..6456de6 100644
--- a/validitysensor/init.py
+++ b/validitysensor/init.py
@@ -6,6 +6,9 @@ from validitysensor.tls import tls
 from validitysensor.sensor import sensor
 from validitysensor.sensor import reboot
 from validitysensor.flash import read_tls_flash
+from validitysensor.init_flash import init_flash
+from validitysensor.upload_fwext import upload_fwext
+from validitysensor.init_db import init_db
 
 def close():
     if usb.dev is not None:
@@ -14,19 +17,26 @@ def close():
         # The reboot command may fail if we're shutting down because the device is already gone.
         try:
             reboot()
+        except RebootException:
+            pass
         finally:
             usb.close()
 
 def open_common():
+    init_flash()
     usb.send_init()
-    # We must register atexit only after we opened usb device, 
-    # so that our handler is called before pyusb's one and we can still talk to the device
-    atexit.register(close)
-
     tls.parseTlsFlash(read_tls_flash())
     tls.open()
-
+    upload_fwext()
     sensor.open()
+    init_db()
+
+    # We must register atexit only after we opened usb device, 
+    # so that our atexit handler is called before pyusb's one and we can still talk to the device
+    #
+    # Don't attempt to autoreboot unless we finished initializing the sensor successfully.
+    # Otherwise if there is a bug in initialization, we may end up in a loop constantly rebooting the device.
+    atexit.register(close)
 
 def open():
     usb.open()
diff --git a/validitysensor/init_db.py b/validitysensor/init_db.py
index d5488f8..aebb49a 100644
--- a/validitysensor/init_db.py
+++ b/validitysensor/init_db.py
@@ -11,8 +11,9 @@ def machine_id_rec_value(b):
     b = b + b'\0' * (0x94 - len(b))
     return pack('<HH', 0x102, len(b)) + b # 0x102 = Machine ID/GUID?
 
+# TODO: make this GUID unique!
 def init_db(machine_guid='e7260876-58db-4d27-8c40-8d13110d6a71'):
-    stg=db.get_user_storage(name='StgWindsor')
+    stg = db.get_user_storage(name='StgWindsor')
     if stg == None:
         print('Creating a new user storage object')
         db.new_user_storate()
@@ -21,7 +22,7 @@ def init_db(machine_guid='e7260876-58db-4d27-8c40-8d13110d6a71'):
 
     if rc == []:
         print('Creating a host machine GUID record')
-        stg=db.get_user_storage(name='StgWindsor')
+        stg = db.get_user_storage(name='StgWindsor')
         db.new_record(stg.dbid, 0x8, stg.dbid, machine_id_rec_value(machine_guid))
         rc = db.get_storage_data()
 
diff --git a/validitysensor/init_flash.py b/validitysensor/init_flash.py
index 641ab53..7744dca 100644
--- a/validitysensor/init_flash.py
+++ b/validitysensor/init_flash.py
@@ -85,14 +85,9 @@ def serialize_partition(p):
     b = b + b'\0'*4 + sha256(b).digest()
     return b
 
-def partition_flash(layout, client_public):
-    info = get_flash_info()
-
+def partition_flash(info, layout, client_public):
     print('Detected Flash IC: %s, %d bytes' % (info.ic.name, info.ic.size))
 
-    if len(info.partitions) > 0:
-        raise Exception('Flash is already partitioned')
-
     cmd = unhex('4f 0000 0000')
     cmd += with_hdr(0, serialize_flash_params(info.ic)) 
     cmd += with_hdr(1, b''.join([serialize_partition(p) for p in layout]) + get_partition_signature())
@@ -108,6 +103,14 @@ def partition_flash(layout, client_public):
     # ^ TODO - figure out what the rest of rsp means
 
 def init_flash():
+    info = get_flash_info()
+
+    if len(info.partitions) > 0:
+        print('Flash has %d partitions.' % len(info.partitions))
+        return
+    else:
+        print('Flash was not initialized yet. Formatting...')
+
     assert_status(usb.cmd(reset_blob))
 
     skey = ec.generate_private_key(ec.SECP256R1(), crypto_backend)
@@ -115,7 +118,7 @@ def init_flash():
     client_private = snums.private_value
     client_public = snums.public_numbers
 
-    partition_flash(flash_layout_hardcoded, client_public)
+    partition_flash(info, flash_layout_hardcoded, client_public)
 
     rsp=usb.cmd(unhex('01'))
     assert_status(rsp)
@@ -150,5 +153,6 @@ def init_flash():
     # Persist certs and keys on cert partition.
     write_flash(1, 0, tls.makeTlsFlash())
 
-    # Reboot
+    # Reboot. 
+    # The device will disconnect and our service will be started by udev as soon as it is connected again.
     reboot()
diff --git a/validitysensor/sensor.py b/validitysensor/sensor.py
index 354b4a7..fa5a4e7 100644
--- a/validitysensor/sensor.py
+++ b/validitysensor/sensor.py
@@ -5,7 +5,7 @@ import os.path
 from .tls import tls
 from .usb import usb
 from .db import db, subtype_to_string
-from .flash import write_enable, flush_changes, read_flash, erase_flash, write_flash_all
+from .flash import write_enable, flush_changes, read_flash, erase_flash, write_flash_all, read_flash_all
 from time import sleep
 from struct import pack, unpack
 from .table_types import SensorTypeInfo, SensorCaptureProg
@@ -55,9 +55,12 @@ def write_hw_reg32(addr, val):
     rsp=tls.cmd(pack('<BLLB', 8, addr, val, 4))
     assert_status(rsp)
 
+class RebootException(Exception):
+    pass
 
 def reboot():
     assert_status(tls.cmd(unhex('050200')))
+    raise RebootException()
 
 def factory_reset():
     assert_status(usb.cmd(reset_blob))
@@ -192,7 +195,7 @@ class CancelledException(Exception):
 class Sensor():
     calib_data=b''
 
-    def open(self, load_calib_data=True):
+    def open(self):
         self.interrupt_cb = None
         self.device_info = identify_sensor()
 
@@ -227,13 +230,7 @@ class Sensor():
         if 7 in factory_bits:
             self.factory_calib_data = factory_bits[7][4:]
 
-        if load_calib_data and os.path.isfile(calib_data_path):
-            with open(calib_data_path, 'rb') as f:
-                self.calib_data = f.read()
-                print('Calibration data loaded from a file.')
-        else:
-            self.calib_data = b''
-            print('Warning: no calibration data was loaded. Consider calibrating the sensor.')
+        self.calibrate()
 
     def save(self):
         with open(calib_data_path, 'wb') as f:
@@ -569,7 +566,43 @@ class Sensor():
 
         write_flash_all(6, 0, clean_slate)
 
+    def check_clean_slate(self):
+        start = read_flash(6, 0, 0x44)
+        magic, l = unpack('<HH', start[:4])
+        start = start[4:]
+
+        if magic != 0x5002:
+            return False
+
+        hs, zeroes = start[0:0x20], start[0x20:0x40]
+        
+        if zeroes != b'\0'*0x20:
+            print('Unexpected contents in calibration flash partition')
+            return False
+
+        img = read_flash_all(6, 0x44, l)
+        if hs != sha256(img).digest():
+            print('Calibration flash hash mismatch')
+            print(hexlify(hs), hexlify(img))
+            return False
+
+        return True
+
+
     def calibrate(self):
+        if os.path.isfile(calib_data_path):
+            with open(calib_data_path, 'rb') as f:
+                self.calib_data = f.read()
+                print('Calibration data loaded from a file.')
+
+            if self.check_clean_slate():
+                return
+            else:
+                print('No calibration data on the flash. Calibrating...')
+        else:
+            self.calib_data = b''
+            print('No calibration data was loaded. Calibrating...')
+
         for i in range(0, self.calibration_iterations):
             print('Calibration iteration %d...' % i)
             rsp = tls.cmd(self.build_cmd_02(CaptureMode.CALIBRATE))
@@ -586,7 +619,7 @@ class Sensor():
         clean_slate = pack('<H', len(clean_slate)) + clean_slate
         clean_slate = clean_slate + pack('<H', 0) # TODO: still don't know what this zero is for
         clean_slate = pack('<H', len(clean_slate)) + sha256(clean_slate).digest() + b'\0'*0x20 + clean_slate
-        clean_slate = unhexlify('0250') + clean_slate
+        clean_slate = pack('<H', 0x5002) + clean_slate
 
         self.persist_clean_slate(clean_slate)
         self.save()
diff --git a/validitysensor/upload_fwext.py b/validitysensor/upload_fwext.py
index 427d23d..be5c073 100644
--- a/validitysensor/upload_fwext.py
+++ b/validitysensor/upload_fwext.py
@@ -23,6 +23,13 @@ def default_fwext_name():
     return '6_07f_lenovo_mis_qm.xpfwext'
 
 def upload_fwext(fw_path=None):
+    fwi=get_fw_info(2)
+    if fwi != None:
+        print('Detected firmware version %d.%d (%s))' % (fwi.major, fwi.minor, ctime(fwi.buildtime)))
+        return
+    else:
+        print('No firmware detected. Uploading...')
+
     # no idea what this is:
     write_hw_reg32(0x8000205c, 7)
     if read_hw_reg32(0x80002080) not in [2, 3]:
@@ -33,6 +40,7 @@ def upload_fwext(fw_path=None):
     # ^ TODO -- what is the real reason to detect HW at this stage?
     #           just a guess: perhaps it is used to construct fwext filename
 
+
     default_name = firmware_home + '/' + default_fwext_name()
     if not fw_path:
         fw_path = default_name
@@ -46,10 +54,6 @@ def upload_fwext(fw_path=None):
     fwext=fwext[fwext.index(b'\x1a')+1:]
     fwext, signature = fwext[:-0x100], fwext[-0x100:]
 
-    fwi=get_fw_info(2)
-    if fwi != None:
-        raise Exception('FW is already present (version %d.%d (%s))' % (fwi.major, fwi.minor, ctime(fwi.buildtime)))
-
     #flush_changes()
     write_flash_all(2, 0, fwext)
     write_fw_signature(2, signature)
@@ -62,3 +66,4 @@ def upload_fwext(fw_path=None):
 
     # Reboot
     reboot()
+    raise Exception('Reboot')