I'm running the "Beacon Application for Eval Board" example for the S110 soft device on an nRF51822.
(devzone.nordicsemi.com/.../a00070.html)
I'm using another BLE device (not Nordic) to read the advertising packet and I'm curious as to some anomalies in its break down.
Here are the raw bytes of the packet I'm getting.
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
Here is my (novice) break-down of the packet:
+----------+-----------------+------------+-------------------+------------------+
| ??? | ACCESS ADDRESS? | PDU HEADER | MAC | LENGTH MFG INFO? |
|----------+-----------------+------------+-------------------+------------------+
| 04 | 3e 2a 02 01 | 03 01 | 5b 31 04 a5 93 d5 | 1e | continued...
+----------+-----------------+------------+-------------------+------------------+
+----------------------------------------------------------------------------+
| MFG INFO A |
+----------------------------------------------------------------------------+
| 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 | continued...
+----------------------------------------------------------------------------+
+--------------+-------------+-----+
| MAJOR, MINOR | TX STRENGTH | CRC |
+--------------+-------------+-----+
| 01 02 03 04 | c3 | c2 |
+--------------+-------------+-----+
Here are my questions:
I don't understand what the 04 at the begining is. It doesn't match what I thought were the only valid preamble values (0x55 or 0xaa).
Why is the Access Address value 0x3e2a0201? That doesn't match what I've seen elsewhere on the internet as the standard Access Address value of 0x8E89BED6 for advertisement packets.
I was under the impression that the second byte of the PDU HEADER was supposed to be the length of the rest of the PDU, but that doesn't seem to be the case with this packet.
I'm curious as to what beacon standard the PDU structure is complying (if any). Most information on the web is for the iBeacon and they don't have the byte after the MAC that I am interpreting as LENGTH MFG INFO or the byte at the end that I'm interpreting as some sort of CRC.
I'm guessing what I perceive as anomalies are just due to some bad information off the inter-webs, but I'm not sure how much of that info is bad and how much is good.
Thanks for helping a noob!
