Important changes to forums and questions
All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.
All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.
1.Profile
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/170918002748097b531234be3d.png[/img]
MTU exchange happens after master and slave device build up connection, refer: "One minute to understand BLE connection data package"
http://www.viewtool.com/forum/vi ... &extra=page%3D1
Below is the comparison of few of major wireless protocol (units: bytes) ************ Ethernet:1500 IEEE 802.3/802.2: 1492 X.25: 576 BLE: 23 (for BLE4.0/4.1), 251 (for BLE4.2) => that's why wifi could be used to transfer video,traditional bluetooth(BT) could be used to transfer audio, and BLE only could be used to transfer control data. **************
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180029b3c7c93cc5b8572a.png[/img]
2.Keyword: Hollong BLE Sniffer, BLE Data Analyzer,BLE Data Capture
3.Preparation before capturing BLE data
http://www.viewtool.com/index.ph ... hollong-4-0-4-1-ble
4. MTU REQEUST Complete data (marked by blue color)
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180035779a121c6a8778a3.png[/img]
1) Access Address: 0xaf9a8c69 Fixed 4 bytes,specified by CONNECT_REQ(see:http://www.viewtool.com/forum/vi ... &extra=page%3D1)
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180033144e751d8b50fe54.png[/img]
2) Header Info Data Header: 0x0706 000. .... = RFU: 0 ...0 .... = More Data: False .... 0... = Sequence Number: 0 .... .1.. = Next Expected Sequence Number: 1 .... ..10 = LLID: Start of an L2CAP message or a complete L2CAP message with no fragmentation (0x2) 000. .... = RFU: 0 ...0 0111 = Length: 7
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/170918003491c7572abed0f3ec.png[/img]
3) L2CAP Length In BLE protocol layer,All of GAP,GATT and SMP use L2CAP channel to transfer command to LINK LAYER,L2CAP packing need to specify L2CAP length and channel ID Length: 3
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180035ae2bfe9d688b3347.png[/img]
4) L2CAP CID:channel ID CID: Attribute Protocol (0x0004)
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180034b5af81e2bd6f7ce2.png[/img]
5) ATT command standard:
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180030578f4b1172870959.png[/img]
actual data package: Opcode: Exchange MTU Request (0x02) 0... .... = Authentication Signature: False .0.. .... = Command: False ..00 0010 = Method: Exchange MTU Request (0x02)
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/17091800350f532761387f8503.png[/img]
6) MTU value (requested) Client Rx MTU: 185
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180034de6ac1eaaa103fd3.png[/img]
7) CRC
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180033da78e5af3f3b9e7a.png[/img]
5. MTU RESPONSE completed data package:
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/170918003823b1d90cfd626450.png[/img]
1) Access Address: 0xaf9a8c69 Fixed 4 bytes,specified by CONNECT_REQ(see:http://www.viewtool.com/forum/vi ... &extra=page%3D1)
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/17091800382afaa000ddbc1eb7.png[/img]
2) Header Info Data Header: 0x0706 000. .... = RFU: 0 ...0 .... = More Data: False .... 0... = Sequence Number: 0 .... .1.. = Next Expected Sequence Number: 1 .... ..10 = LLID: Start of an L2CAP message or a complete L2CAP message with no fragmentation (0x2) 000. .... = RFU: 0 ...0 0111 = Length: 7
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/170918003823c709448fa2b519.png[/img]
3). L2CAP length same as MTU request. Length: 3
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/17091800383491114f1ac9165f.png[/img]
4).L2CAP CID: channel ID same as MTU request. CID: Attribute Protocol (0x0004)
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/170918003856db7b97c94c0975.png[/img]
5). ATT command standard:
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/170918003014935e1c900ca6e2.png[/img]
For this example: Opcode: Exchange MTU Response (0x03) 0... .... = Authentication Signature: False .0.. .... = Command: False ..00 0011 = Method: Exchange MTU Response (0x03)
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180038979c25a1fa04dc4e.png[/img]
6) MTU value Server Rx MTU: 23
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/17091800384d0d949879d8841a.png[/img]
7)CRC CRC: 0xf4767e [Expert Info (Note/Checksum): CRC unchecked, not all data available]
[img]http://www.viewtool.com/forum_bak(20171017)/attachments/month_1709/1709180038972cea8bd39dcaaa.png[/img] For more information,please visit viewtool:http://www.viewtool.com/index.php/en/