UUID 128 bit

RE: UUID 128 bit

Artem Zemlyanukhin — Tue, 14 Jan 2014 13:16:36 GMT

Ok, thanks a lot!

RE: UUID 128 bit

Carles — Tue, 14 Jan 2014 13:08:55 GMT

According to the spec, all UUID values outside the range of the ones reserved by the spec are valid. Also UUIDs are universal by nature, so I believe that you can simply generate them using the tool linked and use them for your purposes. Because the TimeLow value is a timestamp, if you modify it you are effectively generating UUIDs extremely quickly (in time-based generation).

RE: UUID 128 bit

Artem Zemlyanukhin — Tue, 14 Jan 2014 13:01:07 GMT

Carles, thank you for your fats response,

If I set my UUID to any arbitrary value, this may be will not be unique. So can I not worry about the fact that my UUID will not be unique?

RE: UUID 128 bit

Carles — Tue, 14 Jan 2014 12:46:10 GMT

Hi there,

I use nRF51822 with softdevice. To define base UUID I have to use sd_ble_uuid_vs_add(). And then I can add my services with attributes. But their UUIDs will be obtained by defining only byte 12 and byte 13. And this does not match to name based UUIDs, because UUIDs obtained using hash function will be differ not only in 12 and 13 bytes.

The nRF51 solution to handling 128-bit UUIDs is specially tailored for the low memory requirements of an embedded system. It consists of vendor specific 128-bit UUIDs that can be freely set to any value by the user. Those base UUIDs can then be further modified by changing the 2 lower bytes of the TimeLow portion of the UUID (bytes 12 and 13). If your UUIDs can't be extended with this mechanism simply set the base plus bytes 12 and 13 to your required value, but that will use up a base for each VS UUID that you require.

We used this mechanism because it was the SIG's choice when shortening Bluetooth standard 128-bit UUIDs to 16 or 32 bits.

EDIT: According to the spec: "UUID values outside of this range can be allocated as described in [ISO-11578] for any purpose the allocator desires."

You can generate UUIDs here: www.itu.int/.../uuid.html

Carles