1. STM32WB-WBA - Connection Oriented Channel
A COC allows the exchange of Bluetooth® Low Energy data at L2CAP layer without GATT layer. There is no notion of client/server, only central and peripheral.
To set a COC logical link, it is necessary to establish first a Bluetooth® Low Energy link.
Over this Bluetooth® Low Energy link, one or several COC can be established.
The central or the peripheral may be COC initiator.
| Bluetooth® Low Energy Protocol Stack |
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1.1. General L2CAP Terminology
| Bluetooth® Low Energy General L2CAP Terminology |
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1.2. L2CAP Connection Oriented Channel use
1.3. Bluetooth® Low Energy connection and COC establishment initiated by the central
1.3.1. On central side
- Initiate a Bluetooth® Low Energy link: send aci_gap_create_connection
- Wait for HCI_LE_CONNECTION_COMPLETE_EVENT
- Initiate a CoC connection: ACI_L2CAP_COC_CONNECT
- Wait for ACI_L2CAP_COC_CONNECT_CONFIRM_EVENT (get channel_index_list)
Range of channel_index_list for the COC initiator: from 0 to 0x1F
1.3.2. On peripheral side
- Start advertising: send aci_gap_set_discoverable
- Wait for HCI_LE_CONNECTION_COMPLETE_EVENT
- Wait for ACI_L2CAP_COC_CONNECT_EVENT
- Send ACI_L2CAP_COC_CONNECT_CONFIRM
- In hci_command_complete_event, get Channel_number and Channel_Index_List values
Range of channel_index_list for the COC peripheral: from 0x20 to 0x3F
1.4. COC data exchange
1.4.1. On sender side
Send ACI_L2CAP_COC_TX_DATA (Channel_Index, length, data)
1.4.2. On receiver side
Reception of ACI_L2CAP_COC_RX_DATA_EVENT
1.5. Example of Bluetooth® Low Energy connection, COC establishment and data exchange
| Bluetooth® Low Energy and COC link establishment |
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| COC data exchange |
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1.6. Code Example
A STM32WB COC code example has been shared on STM32-Hotspot [1]
A STM32WBA COC code example is available with BLE_SerialCom application