bleak.exc.BleakDBusError: [org.bluez.Error.Failed] Operation failed with ATT error: 0x0e (Unlikely Error)

[ujur007]

• bleak version: latest, installed with pip
• Python version:Python 3.8.10
• Operating System: Linux Mint-64bit
• BlueZ version (bluetoothctl -v) in case of Linux: bluetoothctl: 5.53

Description

I am trying a python script to read & write BLE characteristic values. The issue that I am facing is that while writing to the characteristics. The following output from the terminal.

What I was trying was to write to the specific characteristic with command(write_gatt_char) such as the following. I also tried to change to int:handle instead of string:UUID. I am able to read the characteristic. I am sure that the characteristic is writable, as I have tried it with mobile application.

await client.write_gatt_char("c66f3301-33b3-4687-850a-d52b0d5d1e3e", b'5')

Traceback (most recent call last):
File "testApp.py", line 64, in
asyncio.run(main())
File "/usr/lib/python3.8/asyncio/runners.py", line 44, in run
return loop.run_until_complete(main)
File "/usr/lib/python3.8/asyncio/base_events.py", line 616, in run_until_complete
return future.result()
File "testApp.py", line 46, in main
print(await client.write_gatt_char("c66f3301-33b3-4687-850a-d52b0d5d1e3e", b'5'))
File "/user/.local/lib/python3.8/site-packages/bleak/backends/bluezdbus/client.py", line 720, in write_gatt_char
assert_reply(reply)
File "/user/.local/lib/python3.8/site-packages/bleak/backends/bluezdbus/utils.py", line 22, in assert_reply
raise BleakDBusError(reply.error_name, reply.body)
bleak.exc.BleakDBusError: [org.bluez.Error.Failed] Operation failed with ATT error: 0x0e (Unlikely Error)

Logs

I am new to Wireshark and update the log in this issue.

[ujur007]

I tried to find the solution and what I found was some suggestions.

What I have tried is to downgrade/upgrade the bluez versions but the error still remains the same.
There are some threads also suggesting to increase the packet size on the peripheral device. Which I think should not be an issue, in my case.

[dlech]

Logging Bluetooth packets is really the best way to understand what is going on.

[ujur007]

The write data seems to be not showing up in the traffic on wireshark itself. Here is the Wireshark log for bluetooth0 interface.
What I try todo is establish the connection with remote device using connect() then read all three of the characteristics and then try to write one of the characteristics.

Log_ble.log

[dlech]

Everything is from host to controller, so the device is not responding. It appears to be a problem with the device.

[ujur007]

Ok. I will check with other BLE devices perhaps. Currantly, I have Nimble stack port for esp-idf running on ESP32-pico.

[ujur007]

I have this issue still present in my application. Actually I am simultaneously writing to three characteristics.
What I see happening is that only first write to the characteristic is happening while the latter two are failing.
I have the wireshark log for more information.
wireshark_bluetooth-monitor_20230110174326_mxdjgs.pdf

await self.client.write_gatt_char(first, ([0xFF]))
await self.client.write_gatt_char(second, ([0x00]))
await self.client.write_gatt_char(third, ([0x00]))
        
print(await self.client.read_gatt_char(first))
print(await self.client.read_gatt_char(second))
print(await self.client.read_gatt_char(third))`

[ujur007]

okey, seems the error was in my device code and not with Bleak. So now it works. Thanks..!

[smalik007]

@ujur007, what was the mistake in your code? I am experiencing the same issue when I stress the BLE notification packets too frequently, it suddenly disconnects with device after notifying for few seconds, the issue however is not there when I reduce the messages' frequency. @dlech is there an upper limit in terms of timing we should be aware of, not go beyond to have stable connection?

[dlech]

is there an upper limit in terms of timing we should be aware of, not go beyond to have stable connection?

Not a hard limit. It will depend on the device you are connecting to and the Bluetooth adapter you are using.

[smalik007]

The exception is thrown from the bleak module, which I am running on a Rasberry Pi 2 board which connects to a low energy embedded BLE chip. I suspect the problem more on the Rasberry Pi2 board.