Bluetooth Server Device Name cannot be changed

[axa88]

Library/API/IoT binding

nanoFramework.Device.Bluetooth

Target name(s)

ESP32_PSRAM_BLE_GenericGraphic_REV3

Firmware version

1.15.0.361

Description

It seems that the Bluetooth Server Device Name (Generic Access 0x1800, Device Name 0x2A00) cannot be changed.
Rather it is being hardcoded to "nanoBLE"

How to reproduce

Create server and set:

BluetoothLEServer.Instance.DeviceName
BluetoothLEServer.Instance.Appearance

Observe Generic Access 0x1800, both Device Name 0x2A00 and Appearance 0x2A01 do not get set.

Expected behaviour

It is expected that when setting BluetoothLEServer DeviceName property, it would set this value.

Screenshots

No response

Sample project or code

private readonly BluetoothLEServer _server = BluetoothLEServer.Instance;

_server.DeviceName = "ESP-nf-BLE";
_server.Appearance = (ushort)SubCategory.GenericPhone;
_server.Start();

Aditional information

on a related note, the service's Appearance 0x2A01 isn't being set with its corresponding Appearance property either.

[AdrianSoundy]

Please post the C# code you are using that shows the problem. If it happens on a sample then which sample.

[axa88]

Please post the C# code you are using that shows the problem. If it happens on a sample then which sample.

Sorry, what more would be needed?

To clarify what I'm reporting is that merely setting the BluetoothLEServer singleton instance DeviceName , in any way I believe, will fail to actually set the device name:

private readonly BluetoothLEServer _server = BluetoothLEServer.Instance;
....
_server.DeviceName = "ESP-nf-BLE";
_server.Appearance = (ushort)SubCategory.GenericPhone;

Rather, isn't the value being hardcoded with this?:

[axa88]

fwiw, a bit background conversation about it on discord

[alberk8]

@AdrianSoundy, I have sort of track down the issue. If I set the Device Name (0x2A00) in Generic Access (0x1800) here (after the ble_svc_gap_init())

It seems the code here has no effect before the ble_svc_gap_init() is called.

I think we need to be able to allow for the Device Name (0x2A00) to be different from what is set using BluetoothLEServer.Instance.DeviceName. Basically, the 0X2A00 will be the same as the BluetoothLEServer.Instance.DeviceName if it is not set.

[axa88]

I think we need to be able to allow for the Device Name (0x2A00) to be different from what is set using BluetoothLEServer.Instance.DeviceName.

Perhaps im not fully understanding what you're saying, but this statement doesnt seem right to me.

from the spec:

For a device supporting the LE-only device type, the name is a character string held in the Device Name characteristic as defined in Section 12.1.

It even states that this value should be updatable, as other characteristics usually are, so should be exposed not only as a parameter of a constructor or initializer, but as a set property of a the server.
fwiw, even the Windows sdk, as an example, exposes an event for the device name change.

[alberk8]

I think we need to be able to allow for the Device Name (0x2A00) to be different from what is set using BluetoothLEServer.Instance.DeviceName.

Perhaps im not fully understanding what you're saying, but this statement doesnt seem right to me.

from the spec:

For a device supporting the LE-only device type, the name is a character string held in the Device Name characteristic as defined in Section 12.1.

It even states that this value should be updatable, as other characteristics usually are, so should be exposed not only as a parameter of a constructor or initializer, but as a set property of a the server. fwiw, even the Windows sdk, as an example, exposes an event for the device name change.

What I am saying is the the BluetoothLEServer.Instance.DeviceName (Name you see when Scanning) can be the same or different from the 0x2A00 Device Name (Once connected the Generic Access Service -> Device Name).

[axa88]

What I am saying is the the BluetoothLEServer.Instance.DeviceName (Name you see when Scanning) can be the same or different from the 0x2A00 Device Name (Once connected the Generic Access Service -> Device Name).

Strictly speaking the "name you see while scanning" ie, the name a servers's advertisement may contain, is optional for an LE device. But when included it does have its own set of rules.

The Local Name data type shall be the same as, or a shortened version of, the local name assigned to the device. The Local Name data type value indicates if the name is complete or shortened. If the name is shortened, the complete name can be read using the remote name request procedure over BR/EDR or by reading the device name characteristic after the connection has been established using GATT.

A shortened name shall only contain contiguous characters from the beginning of the full name. For example, if the device name is ‘BT_Device_Name’ then the shortened name could be ‘BT_Device’ or ‘BT_Dev’.

So, implementation I imagine has to go something like this:
Advertisement property LocalName unset, don't advertise a name.
If set and fits in the advertisement packet, use it and mark as data type 0x8.
If it needs to be truncated, truncate until it fits and mark as data type 0x9.
if it doesn't fit at all, mark started incomplete? is that a thing?

So when choosing to advertise the name it should match, it may not as it may not fit even fit. Especially without extended advertising. That's when leaving the name out often makes most sense.

This is probably why most implementations just let you advertise whatever name you want, cuz understanding the spec is a pita

[AdrianSoundy]

I looked quickly into this and see this is a bug.
The code looks OK so I currently don't know why it is happening. I am sure this was working before.

This will require further investigation.