Classic Bluetooth L2CAP API

Application Example

Check bluetooth/bluedroid/classic_bt folder in ESP-IDF examples, which contains the following application:

• This is a BT_L2CAP demo. This demo can connect, send and receive L2CAP data bluetooth/bluedroid/classic_bt/bt_l2cap_client, bluetooth/bluedroid/classic_bt/bt_l2cap_server

API Reference

Header File

• components/bt/host/bluedroid/api/include/api/esp_l2cap_bt_api.h

Functions

esp_err_t esp_bt_l2cap_register_callback(esp_bt_l2cap_cb_t callback)

This function is called to init callbacks with L2CAP module.

Parameters

callback -- [in] pointer to the init callback function.

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_init(void)

This function is called to init L2CAP module. When the operation is completed, the callback function will be called with ESP_BT_L2CAP_INIT_EVT. This function should be called after esp_bluedroid_enable() completes successfully.

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_deinit(void)

This function is called to uninit l2cap module. The operation will close all active L2CAP connection first, then the callback function will be called with ESP_BT_L2CAP_CLOSE_EVT, and the number of ESP_BT_L2CAP_CLOSE_EVT is equal to the number of connection. When the operation is completed, the callback function will be called with ESP_BT_L2CAP_UNINIT_EVT. This function should be called after esp_bt_l2cap_init() completes successfully.

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_connect(esp_bt_l2cap_cntl_flags_t cntl_flag, uint16_t remote_psm, esp_bd_addr_t peer_bd_addr)

This function makes an L2CAP connection to a remote BD Address. When the connection is initiated or failed to initiate, the callback is called with ESP_BT_L2CAP_CL_INIT_EVT. When the connection is established or failed, the callback is called with ESP_BT_L2CAP_OPEN_EVT. This function must be called after esp_bt_l2cap_init() successful and before esp_bt_l2cap_deinit().

Parameters

• cntl_flag -- [in] Lower 16-bit security settings mask.

• remote_psm -- [in] Remote device bluetooth Profile PSM.

• peer_bd_addr -- [in] Remote device bluetooth device address.

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_start_srv(esp_bt_l2cap_cntl_flags_t cntl_flag, uint16_t local_psm)

This function create a L2CAP server and starts listening for an L2CAP connection request from a remote Bluetooth device. When the server is started successfully, the callback is called with ESP_BT_L2CAP_START_EVT. When the connection is established, the callback is called with ESP_BT_L2CAP_OPEN_EVT. This function must be called after esp_bt_l2cap_init() successful and before esp_bt_l2cap_deinit().

Parameters

• cntl_flag -- [in] Lower 16-bit security settings mask.

• local_psm -- [in] Dynamic PSM.

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_stop_all_srv(void)

This function stops all L2CAP servers. The operation will close all active L2CAP connection first, then the callback function will be called with ESP_BT_L2CAP_CLOSE_EVT, and the number of ESP_BT_L2CAP_CLOSE_EVT is equal to the number of connection. When the operation is completed, the callback is called with ESP_BT_L2CAP_SRV_STOP_EVT. This function must be called after esp_bt_l2cap_init() successful and before esp_bt_l2cap_deinit().

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_stop_srv(uint16_t local_psm)

This function stops a specific L2CAP server. The operation will close all active L2CAP connection first on the specific L2CAP server, then the callback function will be called with ESP_BT_L2CAP_CLOSE_EVT, and the number of ESP_BT_L2CAP_CLOSE_EVT is equal to the number of connection. When the operation is completed, the callback is called with ESP_BT_L2CAP_SRV_STOP_EVT. This function must be called after esp_bt_l2cap_init() successful and before esp_bt_l2cap_deinit().

Parameters

local_psm -- [in] Dynamic PSM.

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_vfs_register(void)

This function is used to register VFS. Only supports write, read and close. This function must be called after esp_bt_l2cap_init() successful and before esp_bt_l2cap_deinit().

Returns

• ESP_OK: success

• other: failed

esp_err_t esp_bt_l2cap_vfs_unregister(void)

This function is used to unregister VFS. This function must be called after esp_bt_l2cap_init() successful and before esp_bt_l2cap_deinit().

Returns

• ESP_OK: success

• other: failed

Unions

union esp_bt_l2cap_cb_param_t

#include <esp_l2cap_bt_api.h>

L2CAP callback parameters union.

Public Members

struct esp_bt_l2cap_cb_param_t::l2cap_init_evt_param init

L2CAP callback param of ESP_BT_L2CAP_INIT_EVT

struct esp_bt_l2cap_cb_param_t::l2cap_uninit_evt_param uninit

L2CAP callback param of ESP_BT_L2CAP_UNINIT_EVT

struct esp_bt_l2cap_cb_param_t::l2cap_open_evt_param open

L2CAP callback param of ESP_BT_L2CAP_OPEN_EVT

struct esp_bt_l2cap_cb_param_t::l2cap_close_evt_param close

L2CAP callback param of ESP_BT_L2CAP_CLOSE_EVT

struct esp_bt_l2cap_cb_param_t::l2cap_start_evt_param start

L2CAP callback param of ESP_BT_L2CAP_START_EVT

struct esp_bt_l2cap_cb_param_t::l2cap_cl_init_evt_param cl_init

L2CAP callback param of ESP_BT_L2CAP_CL_INIT_EVT

struct esp_bt_l2cap_cb_param_t::l2cap_srv_stop_evt_param srv_stop

L2CAP callback param of ESP_BT_L2CAP_SRV_STOP_EVT

struct l2cap_cl_init_evt_param

#include <esp_l2cap_bt_api.h>

ESP_BT_L2CAP_CL_INIT_EVT.

Public Members

esp_bt_l2cap_status_t status

status

uint32_t handle

The connection handle

uint8_t sec_id

security ID used by this server

struct l2cap_close_evt_param

#include <esp_l2cap_bt_api.h>

ESP_BT_L2CAP_CLOSE_EVT.

Public Members

esp_bt_l2cap_status_t status

status

uint32_t handle

The connection handle

bool async

FALSE, if local initiates disconnect

struct l2cap_init_evt_param

#include <esp_l2cap_bt_api.h>

ESP_BT_L2CAP_INIT_EVT.

Public Members

esp_bt_l2cap_status_t status

status

struct l2cap_open_evt_param

#include <esp_l2cap_bt_api.h>

ESP_BT_L2CAP_OPEN_EVT.

Public Members

esp_bt_l2cap_status_t status

status

uint32_t handle

The connection handle

int fd

File descriptor

esp_bd_addr_t rem_bda

The peer address

int32_t tx_mtu

The transmit MTU

struct l2cap_srv_stop_evt_param

#include <esp_l2cap_bt_api.h>

ESP_BT_L2CAP_SRV_STOP_EVT.

Public Members

esp_bt_l2cap_status_t status

status

uint8_t psm

local psm

struct l2cap_start_evt_param

#include <esp_l2cap_bt_api.h>

ESP_BT_L2CAP_START_EVT.

Public Members

esp_bt_l2cap_status_t status

status

uint32_t handle

The connection handle

uint8_t sec_id

security ID used by this server

struct l2cap_uninit_evt_param

#include <esp_l2cap_bt_api.h>

ESP_BT_L2CAP_UNINIT_EVT.

Public Members

esp_bt_l2cap_status_t status

status

Macros

ESP_BT_L2CAP_SEC_NONE

Security Setting Mask. Use these three mask mode:

1. ESP_BT_L2CAP_SEC_NONE

2. ESP_BT_L2CAP_SEC_AUTHENTICATE

3. (ESP_BT_L2CAP_SEC_ENCRYPT|ESP_BT_L2CAP_SEC_AUTHENTICATE) No security

ESP_BT_L2CAP_SEC_AUTHORIZE

Authorization required

ESP_BT_L2CAP_SEC_AUTHENTICATE

Authentication required

ESP_BT_L2CAP_SEC_ENCRYPT

Encryption required

Type Definitions

typedef uint32_t esp_bt_l2cap_cntl_flags_t

typedef void (*esp_bt_l2cap_cb_t)(esp_bt_l2cap_cb_event_t event, esp_bt_l2cap_cb_param_t *param)

L2CAP callback function type.

Param event

Event type

Param param

Point to callback parameter, currently is union type

Enumerations

enum esp_bt_l2cap_status_t

L2CAP operation success and failure codes.

Values:

enumerator ESP_BT_L2CAP_SUCCESS

Successful operation.

enumerator ESP_BT_L2CAP_FAILURE

Generic failure.

enumerator ESP_BT_L2CAP_BUSY

Temporarily can not handle this request.

enumerator ESP_BT_L2CAP_NO_RESOURCE

No more resource

enumerator ESP_BT_L2CAP_NEED_INIT

L2CAP module shall init first

enumerator ESP_BT_L2CAP_NEED_DEINIT

L2CAP module shall deinit first

enumerator ESP_BT_L2CAP_NO_CONNECTION

Connection may have been closed

enumerator ESP_BT_L2CAP_NO_SERVER

No server

enum esp_bt_l2cap_cb_event_t

L2CAP callback function events.

Values:

enumerator ESP_BT_L2CAP_INIT_EVT

When L2CAP is initialized, the event comes

enumerator ESP_BT_L2CAP_UNINIT_EVT

When L2CAP is deinitialized, the event comes

enumerator ESP_BT_L2CAP_OPEN_EVT

When L2CAP Client connection open, the event comes

enumerator ESP_BT_L2CAP_CLOSE_EVT

When L2CAP connection closed, the event comes

enumerator ESP_BT_L2CAP_START_EVT

When L2CAP server started, the event comes

enumerator ESP_BT_L2CAP_CL_INIT_EVT

When L2CAP client initiated a connection, the event comes

enumerator ESP_BT_L2CAP_SRV_STOP_EVT

When L2CAP server stopped, the event comes

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