ph4-walkingpad 1.0.2
Walkingpad A1 controller via Bluetooth LE
License: MIT

WalkingPad controller
=====================

Simple python script that can control KingSmith WalkingPad A1. `Others
report <https://github.com/ph4r05/ph4-walkingpad/issues/1>`__ the
similar models, such as R1 PRO work on the same principle.

The belt communicates via `Bluetooth LE
GATT <https://www.oreilly.com/library/view/getting-started-with/9781491900550/ch04.html>`__.
Only one device can be connected to the belt at a time, i.e., if
original app is connected, the controller won’t be able to connect.

Controller features
-------------------

-  Switch mode: Standby / Manual / Automatic
-  Start belt, stop belt
-  Change belt speed (0.5 - 6.0), all options work, e.g. 1.2 not
   originally usable with the native interface (permits only 0.5 step)
-  Change preferences of the belt

   -  Max speed
   -  Start speed
   -  start type (intelli)
   -  Sensitivity in automatic mode
   -  Display
   -  Child lock
   -  Units (miles/km)
   -  Target (time, distance, calories, steps)

-  Ask for current state (speed, time, distance, steps)
-  Ask for last stored state in the WalkingPad

Demo
----

For the best understanding start jupyter-notebook and take a look at
`belt_control.ipynb <belt_control.ipynb>`__

.. code:: bash

   # Install jupyter-notebook
   pip3 install jupyter

   # Start jupyter-notebook in this repository
   jupyter-notebook .

   # open belt_control.ipynb

Library use-case
----------------

The main controller class is ``Controller`` in
`pad.py <ph4_walkingpad/pad.py>`__

Controller
----------

Controller enables to control the belt via CLI shell.

Install the library:

.. code:: bash

   pip install -U ph4-walkingpad

Start controller:

.. code:: bash

   # Note: use module notation to run the script, no direct script invocation.
   python -m ph4_walkingpad.main --stats 750 --json-file ~/walking.json

Or alternatively, if package was installed with pip:

.. code:: bash

   ph4-walkingpad-ctl --stats 750 --json-file ~/walking.json

The command asks for periodic statistics fetching at 750 ms, storing
records to ``~/walking.json``.

Output

::

   ---------------------------------------------------------------------------
       WalkingPad controller

   ---------------------------------------------------------------------------
   $> help

   Documented commands (use 'help -v' for verbose/'help <topic>' for details):
   ===========================================================================
   alias      help     py  quit          set        speed   stop
   ask_stats  history  Q   run_pyscript  shell      start   switch_mode
   edit       macro    q   run_script    shortcuts  status  tasks

   $> status
   WalkingPadCurStatus(dist=0.0, time=0, steps=0, speed=0.0, state=5, mode=2, app_speed=0.06666666666666667, button=2, rest=0000)
   $> start
   $> speed 30
   $> speed 15
   $> status
   WalkingPadCurStatus(dist=0.01, time=16, steps=18, speed=1.8, state=1, mode=1, app_speed=1.5, button=1, rest=0000)
   $> status
   WalkingPadCurStatus(dist=0.01, time=17, steps=20, speed=1.5, state=1, mode=1, app_speed=1.5, button=1, rest=0000)
   $> speed 30
   $> s
   $> WalkingPadCurStatus(dist=0.98, time=670, steps=1195, speed=6.0, state=1, mode=1, app_speed=6.0, button=1, rest=0000), cal:  38.73, net:  30.89, total:  73.65, total net:  57.91
   $> stop
   $> start
   $> speed 30
   $> status

Due to nature of the BluetoothLE callbacks being executed on the main
thread we cannot use readline to read from the console, so the shell CLI
does not support auto-complete, ctrl-r, up-arrow for the last command,
etc. Readline does not have async support at the moment.

OSX Troubleshooting
~~~~~~~~~~~~~~~~~~~

This project uses `Bleak Bluetooth
library <https://github.com/hbldh/bleak>`__. It was reported that OSX
12+ changed Bluetooth scanning logic, so it is not possible to connect
to a device without scanning Bluetooth first. Moreover, it blocks for
the whole timeout interval.

Thus, when using on OSX 12+: - do not use ``-a`` parameter - if there
are more WalkingPads scanned, use ``--filter`` and specify device
address prefix - to modify scanning timeout value use ``--scan-timeout``

Minimal required version of Bleak is 0.14.1

If the process is still crashing, it may be it does not have permissions
to access Bluetooth. To fix it, add your Terminal app (in my case
iTerm2.app) to System Preferences -> Security & Privacy -> Bluetooth.

Related resources: https://github.com/hbldh/bleak/issues/635,
https://github.com/hbldh/bleak/pull/692

Profile
~~~~~~~

If the ``-p profile.json`` argument is passed, profile of the person is
loaded from the file, so the controller can count burned calories. Units
are in a metric system.

.. code:: json

   {
     "id": "user1",
     "male": true,
     "age": 25,
     "weight": 80,
     "height": 1.80,
     "token": "JWT-token",
     "did": "ff:ff:ff:ff:ff:ff",
     "email": "your-account@gmail.com",
     "password": "service-login-password",
     "password_md5": "or md5hash of password, hexcoded, to avoid plaintext password in config"
   }

-  ``did`` is optional field, associates your records with pad MAC
   address when uploading to the service
-  ``email`` and (``password`` or ``password_md5``) are optional. If
   filled, you can call ``login`` to generate a fresh JWT usable for
   service auth.

Note that once you use ``login`` command, other JWTs become invalid,
e.g., on your phone. If you want to use the service on both devices,
login with mobile phone while logging output with ``adb`` and capture
JWT from logs (works only for Android phones).

Stats file
~~~~~~~~~~

The following arguments enable data collection to a statistic file:

::

   --stats 750 --json-file ~/walking.json

In order to guarantee file consistency the format is one JSON record per
file, so it is easy to append to a file at any time without need to read
and rewrite it with each update (helps to prevent a data loss in cause
of a crash).

Example:

::

   {"time": 554, "dist": 79, "steps": 977, "speed": 60, "app_speed": 180, "belt_state": 1, "controller_button": 0, "manual_mode": 1, "raw": "f8a2013c0100022a00004f0003d1b4000000e3fd", "rec_time": 1615644982.5917802, "pid": "ph4r05", "ccal": 23.343, "ccal_net": 18.616, "ccal_sum": 58.267, "ccal_net_sum": 45.644}
   {"time": 554, "dist": 79, "steps": 978, "speed": 60, "app_speed": 180, "belt_state": 1, "controller_button": 0, "manual_mode": 1, "raw": "f8a2013c0100022a00004f0003d2b4000000e4fd", "rec_time": 1615644983.345463, "pid": "ph4r05", "ccal": 23.343, "ccal_net": 18.616, "ccal_sum": 58.267, "ccal_net_sum": 45.644}
   {"time": 555, "dist": 79, "steps": 980, "speed": 60, "app_speed": 180, "belt_state": 1, "controller_button": 0, "manual_mode": 1, "raw": "f8a2013c0100022b00004f0003d4b4000000e7fd", "rec_time": 1615644984.0991402, "pid": "ph4r05", "ccal": 23.476, "ccal_net": 18.722, "ccal_sum": 58.4, "ccal_net_sum": 45.749}
   {"time": 556, "dist": 79, "steps": 981, "speed": 60, "app_speed": 180, "belt_state": 1, "controller_button": 0, "manual_mode": 1, "raw": "f8a2013c0100022c00004f0003d5b4000000e9fd", "rec_time": 1615644984.864169, "pid": "ph4r05", "ccal": 23.608, "ccal_net": 18.828, "ccal_sum": 58.533, "ccal_net_sum": 45.855}
   {"time": 557, "dist": 80, "steps": 982, "speed": 60, "app_speed": 180, "belt_state": 1, "controller_button": 0, "manual_mode": 1, "raw": "f8a2013c0100022d0000500003d6b4000000ecfd", "rec_time": 1615644985.606997, "pid": "ph4r05", "ccal": 23.741, "ccal_net": 18.933, "ccal_sum": 58.665, "ccal_net_sum": 45.961}

The benefit of having detailed data is an option to analyze data from
the whole run, e.g., how step size varies over the time during one
session, collect preferred speeds, etc…

Also, if the original app fails to fetch the final state from the Belt,
having continuous data stream is helpful to avoid data loss.

Reversing Belt API
~~~~~~~~~~~~~~~~~~

Easy way - Android logs
^^^^^^^^^^^^^^^^^^^^^^^

I used the easiest way I found - the original Android application is
quite generously logging all Bluetooth requests and responses; and
network requests and responses (JWT included).

After few trial/error attempts I managed to reverse binary packet
protocol format. See `pad.py </ph4_walkingpad/pad.py>`__ for protocol
internals.

You can query from the belt a status message (app does so each 750 ms,
approx). The status contains speed, distance, steps, and very simple CRC
code (sum of the payload). Interestingly, calories are not part of the
status message and cannot be queried either.

For obtaining logs just plug Android phone via USB, enable development
mode on the phone, enable ADB connection and run:

.. code:: bash

   adb logcat

(Or use AndroidStudio)

You then can see the app communication with the belt in real-time. When
using the app, it logs also requests so you can figure out how commands
for e.g., speed change look like.

Medium - Bluetooth logs
^^^^^^^^^^^^^^^^^^^^^^^

Should vendor remove the logging from the app and you are unable to find
APK in archives with the logging, you can always enable Bluetooth logs
in the Phone development settings.

This approach is not that straightforward as from logs as you cannot see
belt responses in real-time. The Bluetooth log can be obtained from the
device via ``adb`` and opened in Wireshark.

You may need to do own journal with times and commands you issued so you
can experiment with the belt (e.g., change speeds), the commands get
logged to the Bluetooth log. Then after the experiment, download the
Bluetooth log and map your log entries to the packets from the log.

This is substantially difficult compared to the easy way - message logs.

Hard way - Flutter disassembly
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The original application is implemented in
`Flutter <https://flutter.dev>`__, so direct application reversing is
quite painful process. Flutter compiles the source language (TypeScript
I guess) to a binary form. It runs on top of a Flutter virtual machine,
thus compiled binary has only one primary entry point, a dispatch
function. Disassembly does not yield anything sensible, it requires
special tools. Also, decompilation tools require the Flutter version to
precisely match the version used to compile the application.

For those willing to spend time on this:
`1 <https://tinyhack.com/2021/03/07/reversing-a-flutter-app-by-recompiling-flutter-engine/>`__,
`2 <https://www.programmersought.com/article/28206180369/>`__,
`3 <https://rloura.wordpress.com/2020/12/04/reversing-flutter-for-android-wip/>`__,
`4 <https://blog.tst.sh/reverse-engineering-flutter-apps-part-1/>`__.

Hack way - BLE sniffer
^^^^^^^^^^^^^^^^^^^^^^

-  Buy Nordic nRF52832 or nRF52870 USB dongle for BLE sniffing
-  Install plugin to Wireshark

   -  https://www.nordicsemi.com/Products/Development-tools/nRF-Sniffer-for-Bluetooth-LE/Download#infotabs
   -  https://www.szrfstar.com/upload/file/1587092285.pdf

-  In Wireshark, go to View -> Interface Toolbars -> nRF Sniffer for
   Bluetooth LE
-  Let your WalkingPad advertise, then check it in the toolbar
-  Connect with the App to the WalkingPad
-  Analyze captured packet sequence

Manual sniffer capture:

.. code:: bash

   ./nrf_sniffer_ble.sh --extcap-interface /dev/cu.usbserial-0001 --capture --fifo /tmp/fi

Alternatives
^^^^^^^^^^^^

I was using the WalkingPad app to reverse engineer packet formats:

-  https://play.google.com/store/apps/details?id=com.walkingpad.app&hl=en&gl=US
-  https://m.apkpure.com/walkingpad/com.walkingpad.app

Other reported apps may be less obfuscated and easier to analyze (didn’t
test): -
https://play.google.com/store/apps/details?id=com.kingsmith.xiaojin

Protocol basics
---------------

Protocol internals are implemented in
`pad.py <ph4_walkingpad/pad.py>`__.

-  Belt communicates over BT LE GATT messages.
-  Controlling app sends a simple binary message to the belt for control
   and status fetch (request)
-  App sends periodically status requests (~ 750 ms), belt responds with
   a binary message containing: current belt state, manual mode
   indicator, belt running time in seconds, distance in 10 meters (1km =
   100 units), number of steps, last set speed, last button pressed on
   controller (calories are not reported by the belt)
-  Large numbers, such as distance, steps and time are encoded in 3
   bytes in the following form: ``[x0, x1, x2]``, where integer form is
   ``x = x0*65536 + x1*256 + x0`` (big endian on 3 bytes)
-  Packet contains a simple checksum. If the checksum is invalid, belt
   ignores the command. Let ``cmd`` be the whole received payload,
   checksum is computed as: ``cmd[-2] = sum(cmd[1:-2]) % 256``. For
   more, check ``WalkingPadCurStatus``
-  Belt stores the last run status in memory. On query from the app the
   belt returns it in a different status message form, check
   ``WalkingPadLastStatus``. Another request from the app clears the
   last run status.
-  It seems that the belt stores the last run status only for a limited
   time and does not survive power cut, thus this might be the reason
   why users are reporting apps are not fetching the statistics
   completely from the belt. Final stats are fetched after the belt is
   stopped, thus if app is not running when belt stops (e.g., auto stop,
   or by controller), app sometimes does not make the status fetch in
   time and the run status is lost.

Example of a status message ``m``:

::

   f8a2010f01000fd10000ab0012ae3c0000003afd

When logged by the application, it is printed out as array if bytes:

::

   [248, 162, 1, 15, 1, 0, 15, 209, 0, 0, 171, 0, 18, 174, 60, 0, 0, 0, 58, 253]

-  ``[248, 162]`` or ``f8a2`` is a fixed prefix, probably the message
   ID.
-  ``m[2] == 1`` is a belt state
-  ``m[3] == 15`` is a belt speed \* 10, here 1.5 kmph
-  ``m[4] == 1`` is a flag signalizing manual mode (vs automatic = 0)
-  ``m[5:8] == [0, 15, 209]`` is encoded time in seconds, here 4049s =
   67 min, 29s
-  ``m[8:11] == [0, 0, 171]`` is distance in 10 meters, here 171 = 1.71
   km
-  ``m[11:14] == [0, 18, 174]`` is number of steps, here 4782
-  ``m[14] == 60`` is the last set app speed, 60 units, 6 kmph
-  ``m[15]`` unknown
-  ``m[16]`` last controller button pressed
-  ``m[17] == 58`` is the checksum
-  ``m[18] == 253`` is a fixed suffix

Meaning of some fields are not known (15) or the value space was not
explored. ``m[15]`` could be for example heart rate for those models
measuring it.

Related work
~~~~~~~~~~~~

Another reverse engineer of the protocol (under GPL,
`tldr <https://tldrlegal.com/license/gnu-general-public-license-v3-(gpl-3)>`__):
https://github.com/DorianRudolph/QWalkingPad/blob/master/Protocol.h

Thanks
~~~~~~

Thanks to all contributors and to the community.

This project was awarded by the `Google Open Source Peer
Bonus <https://opensource.googleblog.com/2022/03/Announcing-First-Group-of-Google-Open-Source-Peer-Bonus-Winners-in-2022.html>`__
in Feb 2022.

Development
-----------

Install pre-commit hooks defined by ``.pre-commit-config.yaml``

.. code:: shell

   pip3 install -U pre-commit pytest mypy types-requests
   mypy --install-types
   pre-commit install

Auto fix

.. code:: shell

   pre-commit run --all-files

Plugin version update

.. code:: shell

   pre-commit autoupdate

Donate
~~~~~~

Thanks for considering donation if you find this project useful:

Bitcoin
^^^^^^^

::

   1DBr1tfuqv6xphg5rzNTPxqiUbqbRHrM2E

(No Lightning for now, hopefully soon)

Monero
^^^^^^

::

   87KDQUP7yVKd7inmX2WXuaQUBrxeGN9X9AuQwfaUkJ3KQXSRe6KbhnLRvWNK4mx2SeBwcFdHYgS71fzYFS5mtNf7Dn8SdpJ

PayPal
^^^^^^

`PayPal
link <https://www.paypal.com/donate?hosted_button_id=LC2LK4FGHSUCQ>`__