S110 Advertising Access Address and other questions

RE: S110 Advertising Access Address and other questions

QuantumState — Thu, 11 Jun 2015 19:54:27 GMT

Hey, Walter. Sorry I left this sort of hanging. By the time I figured it out, I forgot that I posted this question. I edited my answer to be more correct.

RE: S110 Advertising Access Address and other questions

Walter — Tue, 09 Jun 2015 03:59:02 GMT

Hi, I'm running some tests on different kinds of beacons, and I found out that some of the stuff in that 14 bytes has actually a meaning, and may be not added from bluez. I have no idea about the first 2 bytes (04:3e) but the following 2a is the length of the packet. 02:01:xx is a pattern that shows the AD flags, and 01:xx:xx:xx:xx:xx:xx is the MAC address with 01 as header. The 1e after that is the length of the following MFG info. I agree that the last byte of the packets should be the CRC, but I'm still trying to figure out the meaning of the 04:3e. Since the question is old, do you have any updates to share about this?

RE: S110 Advertising Access Address and other questions

QuantumState — Tue, 23 Sep 2014 18:51:37 GMT

FYI for anyone else following the same learning ramp as me. The packet I was confused by was an HCI (Host Controller Interface) LE (Low Energy) Advertising Report Event. It is defined in the Bluetooth 4.0 spec - Volume 2 Part E Section 7.7.65.2. At least I think that is it. The 1st and 3rd octet of my packet don't seem to conform to that standard, but the rest of the packet does.

RE: S110 Advertising Access Address and other questions

Petter Myhre — Tue, 23 Sep 2014 16:22:36 GMT

Thank you for answering your own question.

RE: S110 Advertising Access Address and other questions

QuantumState — Fri, 29 Aug 2014 21:03:19 GMT

Lots of squinting at the 2000+ page Bluetooth 4.0 spec reveals that this is a host controller interface packet so there are indeed some bits and pieces added by the "host" (i.e. your operating system / driver). The packet decodes thusly:

04:3e:2a:02:01:03:01:5b:31:04:a5:93:d5:1e:02:01:04:1a:ff:4c:00:02:15:01:12:23:34:45:56:67:78:89:9a:ab:bc:cd:de:ef:f0:01:02:03:04:c3:c2

04 - This is an HCI Event packet (See "UART Transport Layer Table 2.1")

3e - The HCI Event Code is an LE Meta Event (See "Host Controller Interface Functional Specification 7.7.65")

2a - The total length of all event parameters is 0x2A octets (See "Host Controller Interface Functional Specification 5.5.4")

02 - The sub-event code is an LE Advertising Report Event (See "Host Controller Interface Functional Specification 7.7.65.2")

01 - There is 1 report in this event (See "Host Controller Interface Functional Specification 7.7.65.2")

03 - The event type is Non connectable undirected advertising (ADV_NONCONN_IND) (See "Host Controller Interface Functional Specification 7.7.65.2")

01 - The address type (of the remote BLE device) is Random Device Address (See "Host Controller Interface Functional Specification 7.7.65.2")

5b:31:04:a5:93:d5 - Device address (of the remote BLE device) (See "Host Controller Interface Functional Specification 7.7.65.2")

1e - The length of the data for the next (i.e. only) report (See "Host Controller Interface Functional Specification 7.7.65.2")

The rest (except the last byte) is a typical Apple Beacon format (you can find definitions of this on Stack Overflow and other places).

c2 - (Last byte) is the RSSI, i.e. the actual received signal strength (See "Host Controller Interface Functional Specification 7.7.65.2")