Linak Desk: BT Error "Attribute can't be written"

[mountainsandcode]

Describe the bug
Appreciate this tool @zewelor - trying to get it working on the IKEA Desk running on a Raspberry Pi. Only deviation from the manual is that I'm not running it in a python venv, but it appears the bug below is unrelated.

If I remember correctly, it works correctly for you with an IKEA Desk? Any pointers would be greatly appreciated!

Debug gateway logs

2020-01-26 17:46:56,666 INFO bt-mqtt-gw gateway.py:61: - Starting
2020-01-26 17:46:56,669 DEBUG bt-mqtt-gw.mqtt mqtt.py:30:init - Setting LWT to: lwt_topic
WARNING: pip is being invoked by an old script wrapper. This will fail in a future version of pip.
Please see pypa/pip#5599 for advice on fixing the underlying issue.
To avoid this problem you can invoke Python with '-m pip' instead of running pip directly.
2020-01-26 17:47:00,069 DEBUG bt-mqtt-gw.workers_manager workers_manager.py:106:register_workers - Added linakdesk worker with 1800 seconds interval and a 35 seconds timeout
2020-01-26 17:47:00,348 DEBUG bt-mqtt-gw.mqtt mqtt.py:116:callbacks_subscription - Subscribing to: linak_desk/update_interval
2020-01-26 17:47:00,349 DEBUG bt-mqtt-gw.mqtt mqtt.py:116:callbacks_subscription - Subscribing to: homeassistant/status
2020-01-26 17:47:00,355 DEBUG bt-mqtt-gw.workers_manager workers_manager.py:174:update_all - Updating all workers
2020-01-26 17:47:01,915 ERROR linak_dpg_bt.connection connection.py:91:make_request - Got exception from bluepy while making a request: Bluetooth command failed (code: 3, error: Attribute can't be written)
2020-01-26 17:47:01,919 ERROR bt-mqtt-gw.workers.linakdesk logger.py:50:log_exception - Error during update of linak desk 'linakdesk' (VALID_MAC): BTLEGattError
Traceback (most recent call last):
File "/home/pi/bt-mqtt-gateway/workers/linakdesk.py", line 43, in _get_height
self.desk.read_dpg_data()
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/linak_device.py", line 83, in read_dpg_data
conn.dpg_command(PROP_DESK_OFFSET)
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/connection.py", line 109, in dpg_command
self.make_request(DPG_COMMAND_HANDLE, value)
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/connection.py", line 92, in make_request
raise ex
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/connection.py", line 86, in make_request
self._conn.writeCharacteristic(handle, value, withResponse=with_response)
File "/usr/local/lib/python3.7/dist-packages/bluepy/btle.py", line 543, in writeCharacteristic
return self._getResp('wr')
File "/usr/local/lib/python3.7/dist-packages/bluepy/btle.py", line 407, in _getResp
resp = self._waitResp(wantType + ['ntfy', 'ind'], timeout)
File "/usr/local/lib/python3.7/dist-packages/bluepy/btle.py", line 368, in _waitResp
raise BTLEGattError("Bluetooth command failed", resp)
bluepy.btle.BTLEGattError: Bluetooth command failed (code: 3, error: Attribute can't be written)
2020-01-26 17:47:01,924 ERROR bt-mqtt-gw logger.py:50:log_exception - Timeout while executing worker command
Traceback (most recent call last):
File "/home/pi/bt-mqtt-gateway/workers/linakdesk.py", line 43, in _get_height
self.desk.read_dpg_data()
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/linak_device.py", line 83, in read_dpg_data
conn.dpg_command(PROP_DESK_OFFSET)
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/connection.py", line 109, in dpg_command
self.make_request(DPG_COMMAND_HANDLE, value)
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/connection.py", line 92, in make_request
raise ex
File "/usr/local/lib/python3.7/dist-packages/linak_dpg_bt/connection.py", line 86, in make_request
self._conn.writeCharacteristic(handle, value, withResponse=with_response)
File "/usr/local/lib/python3.7/dist-packages/bluepy/btle.py", line 543, in writeCharacteristic
return self._getResp('wr')
File "/usr/local/lib/python3.7/dist-packages/bluepy/btle.py", line 407, in _getResp
resp = self._waitResp(wantType + ['ntfy', 'ind'], timeout)
File "/usr/local/lib/python3.7/dist-packages/bluepy/btle.py", line 368, in _waitResp
raise BTLEGattError("Bluetooth command failed", resp)
bluepy.btle.BTLEGattError: Bluetooth command failed (code: 3, error: Attribute can't be written)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "./gateway.py", line 73, in
mqtt.publish(_WORKERS_QUEUE.get(timeout=10).execute())
File "/home/pi/bt-mqtt-gateway/workers_manager.py", line 58, in execute
messages = self._callback(*self._args)
File "/home/pi/bt-mqtt-gateway/workers/linakdesk.py", line 27, in status_update
topic=self.format_topic("height/cm"), payload=self._get_height()
File "/home/pi/bt-mqtt-gateway/workers/linakdesk.py", line 54, in _get_height
raise DeviceTimeoutError
exceptions.DeviceTimeoutError
^C2020-01-26 17:47:26,298 INFO bt-mqtt-gw gateway.py:85: - Finish current jobs and shut down. If you need force exit use kill
`

Server (please complete the following information):

• OS: Linux
• Distro: Raspbian
• Version: Fully up-to-date

[zewelor]

Be sure to use newest Bluez ( https://github.com/zewelor/bt-mqtt-gateway/wiki/Upgrade-Bluez-on-Raspbian ) and pair desk first https://wiki.archlinux.org/index.php/Bluetooth#Pairing . Its always possible that remote used in this desk has some change in protocol and it wont work, without some tweaks.

[mountainsandcode]

Bluez is up-to-date (5.5) and the desk is paired - indeed it appears that the protocol may have changed. Any suggestions for reverse engineering that helped you get the original setup running which you could share? Would be greatly appreciated!

[mountainsandcode]

By the way, this is what I can find with bluetoothctl

[NEW] Primary Service
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service000a
00001801-0000-1000-8000-00805f9b34fb
Generic Attribute Profile
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service000a/char000b
00002a05-0000-1000-8000-00805f9b34fb
Service Changed
[NEW] Descriptor
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service000a/char000b/desc000d
00002902-0000-1000-8000-00805f9b34fb
Client Characteristic Configuration
[NEW] Primary Service
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service000e
99fa0001-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service000e/char000f
99fa0002-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service000e/char0011
99fa0003-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Descriptor
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service000e/char0011/desc0013
00002902-0000-1000-8000-00805f9b34fb
Client Characteristic Configuration
[NEW] Primary Service
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0014
99fa0010-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0014/char0015
99fa0011-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Descriptor
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0014/char0015/desc0017
00002902-0000-1000-8000-00805f9b34fb
Client Characteristic Configuration
[NEW] Primary Service
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0018
99fa0020-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0018/char0019
99fa0021-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Descriptor
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0018/char0019/desc001b
00002902-0000-1000-8000-00805f9b34fb
Client Characteristic Configuration
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0018/char001c
99fa0029-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0018/char001e
99fa002a-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Primary Service
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0020
99fa0030-338a-1024-8a49-009c0215f78a
Vendor specific
[NEW] Characteristic
/org/bluez/hci0/dev_EF_XX_YY_ZZ_AA_BB/service0020/char0021
99fa0031-338a-1024-8a49-009c0215f78a
Vendor specific

[zewelor]

Maybe try to run one of this forks: https://github.com/kbancerz/linak_bt_desk or https://github.com/anetczuk/linak_bt_desk . Maybe they are handling desk better. For general BLE RE something like this: https://medium.com/@urish/reverse-engineering-a-bluetooth-lightbulb-56580fcb7546

I've also dissasembled Android app and used sniffing + reading dissasembled code to describe protcol, but now I don't remember much from it, it was long ago :\

EDIT: Did you registered desk via some android app ? I think there was some setting to allow bluetooth control etc. Maybe you need to turn it on ? Or maybe there is some other procedure now ( on some newer linak remotes etc )

[mountainsandcode]

Hmm, can't get it to work with either of the forks, unfortunately. Thanks for sharing the guide.

I'm using the iOS App, but can't see an option like that unfortunately but I guess that means it's unrestricted (I hope) - I'll see what I can figure out from reverse-engineering.

One small request (not time critical): Any chance you could see if you can extract your list of characteristics using bluetoothctl? Would make it much easier to try to compare what they have changed. No worries if not :)

[zewelor]

Whats the command for characteristis extract ?

[mountainsandcode]

Had a chance to do further debugging on this one - I tried using some alternative scripts for the debugging. With https://github.com/apicore-engineering/linaktray, I can read out the state (i.e. height) of the desk without any problems, but I can't subscribe to changes or control the desk to a specific height. Appears to me (not being an expert) this may be a hardware limitation of the IDASEN desk

[zewelor]

It might be that auto move is disabled is this controller. In mine I had to turn it on explicit via app ( and there was info not every controller will allow it ). Maybe you can find other controller and swap it ( not sure if there is any authorization between desk / controller )

[angadsingh]

if auto move is disabled, how are all of. the following able to do it:
https://github.com/j5lien/esphome-idasen-desk-controller
https://apps.apple.com/us/app/desk-remote-control/id1509037746
https://github.com/DWilliames/idasen-controller-mac