Relation between 16- and 128-bit UUIDs

[marco.genise]

When using custom 128-bit base UUIDs and 16-bit UUIDs to address services or characteristics within the formerly specified base UUID, it seems the Nordic softdevices always build the resulting UUID by replacing bytes 12 and 13 of the base UUID with the 16-bit UUID (the digits 'X' in this sample UUID: 8353XXXX-14ee-11e9-ab14-d663bd873d93).

I understand this rule is used for 16-bit UUIDs within the Bluetooth SIG base UUID and thus the Nordic softdevice can handle custom services more efficiently when following this rule for these custom services, too.

My question finally is: is this required by the Bluetooth specifications to always build resulting UUIDs by placing the 16-bit UUID to bytes 12 and 13? I know of the specification of this regarding the Bluetooth SIG base UUID, but not for custom UUIDs.

Thank you in advance!

[AndreasF]

Hi.

My question finally is: is this required by the Bluetooth specifications to always build resulting UUIDs by placing the 16-bit UUID to bytes 12 and 13? I know of the specification of this regarding the Bluetooth SIG base UUID, but not for custom UUIDs.

If I understood the rest of your text correctly, then the answer is yes.

Best regards,

Andreas

[marco.genise]

Hi Andreas,

could you please provide a source for your answer (e.g. Bluetooth Core Spec?)?

Best regards,

Marco.

[AndreasF]

Hi Marco.

I understand this rule is used for 16-bit UUIDs within the Bluetooth SIG base UUID and thus the Nordic softdevice can handle custom services more efficiently when following this rule for these custom services, too.

 This is true.

marco.genise said:

could you please provide a source for your answer (e.g. Bluetooth Core Spec?)?

 Bluetooth Core Spec 4.2 chapter 2.5.1 - UUID

The SoftDevice follows the rules of this Chapter.

This is the arithmetic operation from the Bluetooth Core Spec used by the SoftDevice.

Best regards,

Andreas

[marco.genise]

Hi Andreas,

I know this chapter within the Bluetooth Core Specification. Actually I read this as an explicit rule targeting the relation between 16- or 32-bit assigned numbers and the Bluetooth base UUID. I don't understand this chapter as a general rule beside this.

Best regards,

Marco.

[AndreasF]

Hi Marco.

marco.genise said:

I don't understand this chapter as a general rule beside this.

 I'm a bit unsure if this is a question and you wish to have some explanation about this chapter.

Best regards,

Andreas