Overview:
In the BLE connection process, there are three key data packets: SCAN_REQ, SCAN_RSP, and CONNECT_REQ. SCAN_REQ is a scan request sent by the master device to the slave device to gather more details about the device being broadcast, such as its name, service UUID, and other vendor-specific information like hardware and software versions or serial numbers. SCAN_RSP is the response from the slave device to the SCAN_REQ, providing supplementary data to the broadcast packet. CONNECT_REQ is the connection request sent by the master to the slave, marking the establishment of the connection.
Keywords:
Hollong BLE Listener, Bluetooth Low Energy Sniffer, BLE Analyzer, BLE Data Capture
Preparation for Capturing Connection Data:
To capture these data packets, you’ll need:
- A BLE device (slave) and its corresponding master device (like a smartphone app or universal BLE tool software).
- A Hollong BLE Sniffer.
- Hollong Bluetooth 4.0/4.1 BLE Protocol Monitor Analyzer Software. Download link: [insert link].
SCAN_REQ Packet:
1. Complete Packet Structure: Includes the access address, header info, device addresses, and CRC.
2. Access Address: Fixed at 4 bytes with the content 0x8e89bed6.
3. Header Info: Fixed at 2 bytes, split into 16 bits, defining various parameters including the PDU type (e.g., SCAN_REQ).
4. Master Device Address: The address of the master device initiating the scan request.
5. Slave Device Address: The address of the slave device responding to the scan request.
6. CRC: Used for error checking.
SCAN_RSP Packet:
1. Access Address: Similar to SCAN_REQ.
2. Header Info: Same structure as SCAN_REQ.
3. Slave Address: Fixed at 6 bytes representing the MAC address.
4. Response Data: Contains broadcast data, formatted similarly to broadcast data.
5. CRC: Fixed at 3 bytes for error checking.
CONNECT_REQ Packet:
1. Access Address: Fixed at 4 bytes with the content 0x8e89bed6.
2. Header Info: Two bytes analyzing the connection request.
3. Master Address: The address of the master device requesting the connection.
4. Slave Address: The address of the slave device receiving the connection request.
5. Access Address: Specifies the access address for the BLE data channel post-connection.
6. CRC INIT: Initial CRC value for subsequent data checks.
7. Window Size: Defines the window size for connection attempts.
8. Window Offset: Specifies the timing offset for the connection attempt.
9. Connection Interval: Defines the interval between data packets.
10. Latency: Indicates the connection latency.
11. Timeout: Maximum delay before considering the connection lost.
12. Channel Map: Specifies the frequency hopping pattern.
13. HOP and CLOCK: Defines the hopping data and clock accuracy.
14. CRC: Error checking mechanism.
The stability and reliability of BLE communication are enhanced through frequency hopping, which allows devices to switch to less congested channels, improving data transmission efficiency. This is particularly effective in environments with minimal interference.
Feel free to experiment with different tools and settings to better understand BLE communication dynamics. If you encounter issues, consider consulting further resources or forums for additional support.
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