Setting DIS serial number at runtime

[grzegorz]

How can I set serial number visible in DIS service programaticaly? I know I can set CONFIG_BT_DIS_SERIAL_NUMBER_STR, but putting serial number in project's source code makes no sense. Serial number should be unique for each device. So I'd like to read it using hw_id_get() and put it into DIS. In old Nordic SDK it was trivial. In Connect SDK it seems to be not possible.

[Vidar Berg]

Hello,

You can load the serial number at runtime using the settings module as demonstrated by the Bluetooth: Peripheral DIS sample in the Zephyr repo. 

Best regards,

Vidar

[grzegorz]

Hello Vidar Berg 

I hoped settings module won't be necessary. It's not very flexible because if I want to use it for serial number then I must use it for HW/SW versions as well. And using settings module means copying from Flash to Flash (version) or ROM to Flash (unique chip number as serial number) which is not optimal.

Anyway settings module solves the problem, thanks for help.

Best regards,

Grzegorz

[Vidar Berg]

Hello Grzegorz,

In the sample, the settings module is only used to apply the settings. It doesn't actually use any flash backend.

Best regards,

Vidar

[grzegorz]

When I read Zephyr documentation I was sure Settings must use some backend (FILE, FCB, NFS). So backend is optional and just RAM is used in this sample?

[Vidar Berg]

Correct. I guess the rationale for using the settings module in the first place is that it enables DIS data to be kept in flash for those that need it. Personally, I think it would have been better to provide APIs to modify these values.

[grzegorz]

Hi Vidar Berg 

Yes, API would be better. But if runtime settings don't touch Flash then it's not that bad.

Regarding the sample. It sets CONFIG_SETTINGS_NONE=y. Is it required by runtime settings? I guess runtime settings are always in RAM? Additionally I think CONFIG_SETTINGS_NVS=y is needed anyway because without it I get errors from bt module:

00> [00561318] <err> bt_gatt: Failed to save Database Hash (err -2)
00> [00561356] <err> bt_settings: Failed to save ID (err -2)
00> [00561370] <err> bt_settings: Failed to save IRK (err -2)

Regards,

Grzegorz

[Vidar Berg]

Hi Grzegorz,

Yes, you need to enable the NVS backend if you have a Bluetooth application with support for bonding enabled. The Bluetooth host uses the settings module to store bonding information in persistent memory.

Regards,

Vidar