Controller & HCI
Application Examples
- bluetooth/hci/ble_adv_scan_combined demonstrates how to use Bluetooth capabilities for advertising and scanning with a virtual Host Controller Interface (HCI). This example shows how to implement some host functionalities without a host and displays scanned advertising reports from other devices. 
- bluetooth/hci/controller_hci_uart_esp32 demonstrates how to configure the Bluetooth LE Controller's HCI to communicate over UART on ESP32, enabling communication with an external Bluetooth host stack. 
- bluetooth/hci/controller_vhci_ble_adv demonstrates how to use the ESP-IDF VHCI ble_advertising app to perform advertising without a host and display received HCI events from the controller. 
API Reference
Header File
- This header file can be included with: - #include "esp_bt.h" 
- This header file is a part of the API provided by the - btcomponent. To declare that your component depends on- bt, add the following to your CMakeLists.txt:- REQUIRES bt - or - PRIV_REQUIRES bt 
Functions
- 
esp_err_t esp_bt_controller_init(esp_bt_controller_config_t *cfg)
- Initialize the Bluetooth Controller to allocate tasks and other resources. - Note - This function should be called only once, before any other Bluetooth functions. - Parameters:
- cfg -- [in] Initial Bluetooth Controller configuration 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
- ESP_ERR_INVALID_ARG: Invalid arguments 
- ESP_ERR_NO_MEM: Out of memory 
 
 
- 
esp_err_t esp_bt_controller_deinit(void)
- De-initialize Bluetooth Controller to free resources and delete tasks. - Note - You should stop advertising and scanning, and disconnect all existing connections before de-initializing Bluetooth Controller. 
- This function should be called after - esp_bt_controller_disableif the Controller was enabled before.
- This function should be called only once, after any other Bluetooth functions. 
 - Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
 
 
- 
esp_err_t esp_bt_controller_enable(esp_bt_mode_t mode)
- Enable Bluetooth Controller. - For API compatibility, retain this argument. This mode must match the mode specified in the - cfgof- esp_bt_controller_init().- Note - Bluetooth Controller cannot be enabled in - ESP_BT_CONTROLLER_STATUS_IDLEstatus. It has to be initialized first.
- Due to a known issue, you cannot call - esp_bt_controller_enable()for the second time to change the Controller mode dynamically. To change the Controller mode, call- esp_bt_controller_disable()and then call- esp_bt_controller_enable()with the new mode.
 - Parameters:
- mode -- [in] The Bluetooth Controller mode (BLE/Classic Bluetooth/BTDM) to enable 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
- ESP_ERR_INVALID_ARG: Invalid arguments 
 
 
- 
esp_err_t esp_bt_controller_disable(void)
- Disable Bluetooth Controller. - Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
 
 
- 
esp_bt_controller_status_t esp_bt_controller_get_status(void)
- Get Bluetooth Controller status. - Returns:
- ESP_BT_CONTROLLER_STATUS_IDLE: The Controller is not initialized or has been de-initialized. 
- ESP_BT_CONTROLLER_STATUS_INITED: The Controller has been initialized, but not enabled or has been disabled. 
- ESP_BT_CONTROLLER_STATUS_ENABLED: The Controller has been initialized and enabled. 
 
 
- 
esp_err_t esp_bt_controller_mem_release(esp_bt_mode_t mode)
- Release the Controller memory as per the mode. - This function releases the BSS, data and other sections of the Controller to heap. The total size is about 70 KB. - If you never intend to use Bluetooth in a current boot-up cycle, calling - esp_bt_controller_mem_release(ESP_BT_MODE_BTDM)could release the BSS and data consumed by both Classic Bluetooth and BLE Controller to heap.- If you intend to use BLE only, calling - esp_bt_controller_mem_release(ESP_BT_MODE_CLASSIC_BT)could release the BSS and data consumed by Classic Bluetooth Controller. You can then continue using BLE.- If you intend to use Classic Bluetooth only, calling - esp_bt_controller_mem_release(ESP_BT_MODE_BLE)could release the BSS and data consumed by BLE Controller. You can then continue using Classic Bluetooth.- Note - This function is optional and should be called only if you want to free up memory for other components. 
- This function should only be called when the Controller is in - ESP_BT_CONTROLLER_STATUS_IDLEstatus.
- Once Bluetooth Controller memory is released, the process cannot be reversed. This means you cannot use the Bluetooth Controller mode that you have released using this function. 
- If your firmware will upgrade the Bluetooth Controller mode later (such as switching from BLE to Classic Bluetooth or from disabled to enabled), then do not call this function. 
 - Parameters:
- mode -- [in] The Bluetooth Controller mode 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
- ESP_ERR_NOT_FOUND: Requested resource not found 
 
 
- 
esp_err_t esp_bt_mem_release(esp_bt_mode_t mode)
- Release the Controller memory, BSS and data section of the Classic Bluetooth/BLE Host stack as per the mode. - This function first releases Controller memory by internally calling - esp_bt_controller_mem_release(), then releases Host memory.- If you never intend to use Bluetooth in a current boot-up cycle, calling - esp_bt_mem_release(ESP_BT_MODE_BTDM)could release the BSS and data consumed by both Classic Bluetooth and BLE stack to heap.- If you intend to use BLE only, calling - esp_bt_mem_release(ESP_BT_MODE_CLASSIC_BT)could release the BSS and data consumed by Classic Bluetooth. You can then continue using BLE.- If you intend to use Classic Bluetooth only, calling - esp_bt_mem_release(ESP_BT_MODE_BLE)could release the BSS and data consumed by BLE. You can then continue using Classic Bluetooth.- For example, if you only use Bluetooth for setting the Wi-Fi configuration, and do not use Bluetooth in the rest of the product operation, after receiving the Wi-Fi configuration, you can disable/de-init Bluetooth and release its memory. Below is the sequence of APIs to be called for such scenarios: - esp_bluedroid_disable(); esp_bluedroid_deinit(); esp_bt_controller_disable(); esp_bt_controller_deinit(); esp_bt_mem_release(ESP_BT_MODE_BTDM); - Note - This function is optional and should be called only if you want to free up memory for other components. 
- This function should only be called when the Controller is in - ESP_BT_CONTROLLER_STATUS_IDLEstatus.
- Once Bluetooth Controller memory is released, the process cannot be reversed. This means you cannot use the Bluetooth Controller mode that you have released using this function. 
- If your firmware will upgrade the Bluetooth Controller mode later (such as switching from BLE to Classic Bluetooth or from disabled to enabled), then do not call this function. 
 - Parameters:
- mode -- [in] The Bluetooth Controller mode 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
- ESP_ERR_NOT_FOUND: Requested resource not found 
 
 
- 
esp_err_t esp_bt_sleep_enable(void)
- Enable Bluetooth modem sleep. - There are currently two options for Bluetooth modem sleep: ORIG mode and EVED mode. The latter is intended for BLE only. The modem sleep mode could be configured in menuconfig. - In ORIG mode, if there is no event to process, the Bluetooth Controller will periodically switch off some components and pause operation, then wake up according to the scheduled interval and resume work. It can also wakeup earlier upon external request using function - esp_bt_controller_wakeup_request().- Note - This function shall not be invoked before - esp_bt_controller_enable().- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
- ESP_ERR_NOT_SUPPORTED: Operation or feature not supported 
 
 
- 
esp_err_t esp_bt_sleep_disable(void)
- Disable Bluetooth modem sleep. - Note - Bluetooth Controller will not be allowed to enter modem sleep after calling this function. 
- In ORIG modem sleep mode, calling this function may not immediately wake up the Controller if it is currently dormant. In this case, - esp_bt_controller_wakeup_request()can be used to shorten the wake-up time.
- This function shall not be invoked before - esp_bt_controller_enable().
 - Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
- ESP_ERR_NOT_SUPPORTED: The modem sleep mode is not supported 
 
 
- 
esp_err_t esp_ble_tx_power_set(esp_ble_power_type_t power_type, esp_power_level_t power_level)
- Set BLE TX power. - Note - Connection TX power should only be set after the connection is established. - Parameters:
- power_type -- [in] The type of TX power. It could be Advertising, Connection, Default, etc. 
- power_level -- [in] Power level (index) corresponding to the absolute value (dBm) 
 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_ARG: Invalid argument 
 
 
- 
esp_power_level_t esp_ble_tx_power_get(esp_ble_power_type_t power_type)
- Get BLE TX power. - Note - Connection TX power should only be retrieved after the connection is established. - Parameters:
- power_type -- [in] The type of TX power. It could be Advertising/Connection/Default and etc. 
- Returns:
- Power level 
 
 
- 
esp_err_t esp_ble_scan_duplicate_list_flush(void)
- Manually clear the BLE scan duplicate list. - Note - This function name is incorrectly spelled, it will be fixed in release 5.x version. 
- The scan duplicate list will be automatically cleared when the maximum amount of devices in the filter is reached. The amount of devices in the filter can be configured in menuconfig. 
 - Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
 
 
- 
esp_err_t esp_bredr_tx_power_set(esp_power_level_t min_power_level, esp_power_level_t max_power_level)
- Set BR/EDR TX power. - BR/EDR power control will use the power within the range of minimum value and maximum value. The power level will affect the global BR/EDR TX power for operations such as inquiry, page, and connection. - Note - Please call this function after - esp_bt_controller_enable()and before any functions that cause RF transmission, such as performing discovery, profile initialization, and so on.
- For BR/EDR to use the new TX power for inquiry, call this function before starting an inquiry. If BR/EDR is already inquiring, restart the inquiry after calling this function. 
 - Parameters:
- min_power_level -- [in] The minimum power level. The default value is - ESP_PWR_LVL_N0.
- max_power_level -- [in] The maximum power level. The default value is - ESP_PWR_LVL_P3.
 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_ARG: Invalid argument 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
 
 
- 
esp_err_t esp_bredr_tx_power_get(esp_power_level_t *min_power_level, esp_power_level_t *max_power_level)
- Get BR/EDR TX power. - The corresponding power levels will be stored into the arguments. - Parameters:
- min_power_level -- [out] Pointer to store the minimum power level 
- max_power_level -- [out] The maximum power level 
 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_ARG: Invalid argument 
 
 
- 
esp_err_t esp_bredr_sco_datapath_set(esp_sco_data_path_t data_path)
- Set BR/EDR default SCO data path. - Note - This function should be called after the Controller is enabled, and before (e)SCO link is established. - Parameters:
- data_path -- [in] SCO data path 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_STATE: Invalid Bluetooth Controller state 
 
 
- 
bool esp_vhci_host_check_send_available(void)
- Check whether the Controller is ready to receive the HCI data from the Host. - If the return value is True, the Host can send the HCI data to the Controller. - Note - This function should be called before each - esp_vhci_host_send_packet().- Returns:
- True if the Controller is ready to receive the HCI data; false otherwise 
 
- 
void esp_vhci_host_send_packet(uint8_t *data, uint16_t len)
- Send the HCI data to the Controller. - Note - This function shall not be called within a critical section or when the scheduler is suspended. 
- This function should be called only if - esp_vhci_host_check_send_available()returns True.
 - Parameters:
- data -- [in] Pointer to the HCI data 
- len -- [in] The HCI data length 
 
 
- 
esp_err_t esp_vhci_host_register_callback(const esp_vhci_host_callback_t *callback)
- Register the VHCI callback functions defined in - esp_vhci_host_callbackstructure.- Parameters:
- callback -- [in] - esp_vhci_host_callbacktype variable
- Returns:
- ESP_OK: Success 
- ESP_FAIL: Failure 
 
 
- 
esp_bt_sleep_clock_t esp_bt_get_lpclk_src(void)
- Get the Bluetooth module sleep clock source. - Note - This function should be called after - esp_bt_controller_init()- Returns:
- Clock source used in Bluetooth low power mode 
 
 
- 
esp_err_t esp_bt_set_lpclk_src(esp_bt_sleep_clock_t lpclk)
- Set the Bluetooth module sleep clock source. - Note - This function should be called before - esp_bt_controller_init()- Parameters:
- lpclk -- [in] Bluetooth sleep clock source 
- Returns:
- ESP_OK: Success 
- ESP_ERR_INVALID_ARG: Invalid argument 
 
 
Structures
- 
struct esp_bt_controller_config_t
- Bluetooth Controller config options. - Note - For parameters configurable through menuconfig, it is recommended to adjust them via the menuconfig interface. Please refer to menuconfig for details on the range and default values. 
- It is not recommended to modify the values for parameters which are not configurable through menuconfig. 
 - Public Members - 
uint16_t controller_task_stack_size
- Bluetooth Controller task stack size in bytes 
 - 
uint8_t controller_task_prio
- Bluetooth Controller task priority 
 - 
uint8_t hci_uart_no
- UART number as HCI I/O interface. Configurable in menuconfig. - 1 - URAT 1 (default) 
- 2 - URAT 2 
 
 - 
uint32_t hci_uart_baudrate
- UART baudrate. Configurable in menuconfig. - Range: 115200 - 921600 
- Default: 921600 
 
 - 
uint8_t scan_duplicate_mode
- Scan duplicate filtering mode. Configurable in menuconfig. - 0 - Normal scan duplicate filtering mode (default) 
- 1 - Special scan duplicate filtering mode for BLE Mesh 
 
 - 
uint8_t scan_duplicate_type
- Scan duplicate filtering type. If - scan_duplicate_modeis set to 1, this parameter will be ignored. Configurable in menuconfig.- 0 - Filter scan duplicates by device address only (default) 
- 1 - Filter scan duplicates by advertising data only, even if they originate from different devices. 
- 2 - Filter scan duplicated by device address and advertising data. 
 
 - 
uint16_t normal_adv_size
- Maximum number of devices in scan duplicate filtering list. Configurable in menuconfig - Range: 10 - 1000 
- Default: 100 
 
 - 
uint16_t mesh_adv_size
- Maximum number of Mesh advertising packets in scan duplicate filtering list. Configurable in menuconfig - Range: 10 - 1000 
- Default: 100 
 
 - 
uint16_t send_adv_reserved_size
- Controller minimum memory value in bytes. Internal use only 
 - 
uint32_t controller_debug_flag
- Controller debug log flag. Internal use only 
 - 
uint8_t mode
- Controller mode. Configurable in menuconfig - 1 - BLE mode 
- 2 - Classic Bluetooth mode 
- 3 - Dual mode 
- 4 - Others: Invalid 
 
 - 
uint8_t ble_max_conn
- Maximum number of BLE connections. Configurable in menuconfig - Range: 1 - 9 
- Default: 3 
 
 - 
uint8_t bt_max_acl_conn
- Maximum number of BR/EDR ACL connections. Configurable in menuconfig - Range: 1 - 7 
- Default: 2 
 
 - 
uint8_t bt_sco_datapath
- SCO data path. Configurable in menuconfig - 0 - HCI module (default) 
- 1 - PCM module 
 
 - 
bool auto_latency
- True if BLE auto latency is enabled, used to enhance Classic Bluetooth performance in the Dual mode; false otherwise (default). Configurable in menuconfig 
 - 
bool bt_legacy_auth_vs_evt
- True if BR/EDR Legacy Authentication Vendor Specific Event is enabled (default in the classic bluetooth or Dual mode), which is required to protect from BIAS attack; false otherwise. Configurable in menuconfig 
 - 
uint8_t bt_max_sync_conn
- Maximum number of BR/EDR synchronous connections. Configurable in menuconfig - Range: 0 - 3 
- Default: 0 
 
 - 
uint8_t ble_sca
- BLE low power crystal accuracy index. Configurable in menuconfig - 0 - - BTDM_BLE_DEFAULT_SCA_500PPM
- 1 - - BTDM_BLE_DEFAULT_SCA_250PPM(default)
 
 - 
uint8_t pcm_role
- PCM role. Configurable in menuconfig - 0 - PCM master (default) 
- 1 - PCM slave (default) 
 
 - 
uint8_t pcm_polar
- PCM polarity (falling clk edge & rising clk edge). Configurable in menuconfig - 0 - Falling Edge (default) 
- 1 - Rising Edge 
 
 - 
uint8_t pcm_fsyncshp
- Physical shape of the PCM Frame Synchronization signal. Configurable in menuconfig - 0 - Stereo Mode (default) 
- 1 - Mono Mode 1 
- 2 - Mono Mode 2 
 
 - 
bool hli
- True if using high-level (level 4) interrupt (default); false otherwise. Configurable in menuconfig 
 - 
uint8_t enc_key_sz_min
- Minimum size of the encryption key - Range: 7 - 16 
- Default: 7 
 
 - 
uint16_t dup_list_refresh_period
- Scan duplicate filtering list refresh period in seconds. Configurable in menuconfig - Range: 0 - 100 seconds 
- Default: 0 second 
 
 - 
bool ble_scan_backoff
- True if BLE scan backoff is enabled; false otherwise (default). Configurable in menuconfig 
 - 
uint8_t ble_llcp_disc_flag
- Flag indicating whether the Controller disconnects after Instant Passed (0x28) error occurs. Configurable in menuconfig. - The Controller does not disconnect after Instant Passed (0x28) by default. 
 
 - 
bool ble_aa_check
- True if adds a verification step for the Access Address within the - CONNECT_INDPDU; false otherwise (default). Configurable in menuconfig
 - 
uint8_t ble_chan_ass_en
- True if BLE channel assessment is enabled (default), false otherwise. Configurable in menuconfig 
 - 
uint8_t ble_ping_en
- True if BLE ping procedure is enabled (default), false otherwise. Configurable in menuconfig 
 - 
uint32_t magic
- Magic number 
 
- 
struct esp_vhci_host_callback
- Virtual HCI (VHCI) callback functions to notify the Host on the next operation. 
Macros
- 
ESP_BT_CONTROLLER_CONFIG_MAGIC_VAL
- Internal use only. - Note - Please do not modify this value 
- 
BT_CONTROLLER_INIT_CONFIG_DEFAULT()
- Default Bluetooth Controller configuration. 
Type Definitions
- 
typedef struct esp_vhci_host_callback esp_vhci_host_callback_t
- Virtual HCI (VHCI) callback functions to notify the Host on the next operation. 
Enumerations
- 
enum esp_bt_mode_t
- Bluetooth Controller mode. - Values: - 
enumerator ESP_BT_MODE_IDLE
- Bluetooth is not operating. 
 - 
enumerator ESP_BT_MODE_BLE
- Bluetooth is operating in BLE mode. 
 - 
enumerator ESP_BT_MODE_CLASSIC_BT
- Bluetooth is operating in Classic Bluetooth mode. 
 - 
enumerator ESP_BT_MODE_BTDM
- Bluetooth is operating in Dual mode. 
 
- 
enumerator ESP_BT_MODE_IDLE
- 
enum esp_ble_sca_t
- BLE sleep clock accuracy (SCA) - Note - Currently only ESP_BLE_SCA_500PPM and ESP_BLE_SCA_250PPM are supported. - Values: - 
enumerator ESP_BLE_SCA_500PPM
- BLE SCA at 500 ppm 
 - 
enumerator ESP_BLE_SCA_250PPM
- BLE SCA at 250 ppm 
 - 
enumerator ESP_BLE_SCA_150PPM
- BLE SCA at 150 ppm 
 - 
enumerator ESP_BLE_SCA_100PPM
- BLE SCA at 100 ppm 
 - 
enumerator ESP_BLE_SCA_75PPM
- BLE SCA at 75 ppm 
 - 
enumerator ESP_BLE_SCA_50PPM
- BLE SCA at 50 ppm 
 - 
enumerator ESP_BLE_SCA_30PPM
- BLE SCA at 30 ppm 
 - 
enumerator ESP_BLE_SCA_20PPM
- BLE SCA at 20 ppm 
 
- 
enumerator ESP_BLE_SCA_500PPM
- 
enum esp_bt_controller_status_t
- Bluetooth Controller status. - Values: - 
enumerator ESP_BT_CONTROLLER_STATUS_IDLE
- The Controller is not initialized or has been de-initialized. 
 - 
enumerator ESP_BT_CONTROLLER_STATUS_INITED
- The Controller has been initialized, but not enabled or has been disabled. 
 - 
enumerator ESP_BT_CONTROLLER_STATUS_ENABLED
- The Controller has been initialized and enabled. 
 - 
enumerator ESP_BT_CONTROLLER_STATUS_NUM
- Number of Controller statuses 
 
- 
enumerator ESP_BT_CONTROLLER_STATUS_IDLE
- 
enum esp_ble_power_type_t
- BLE TX power type. - Note - The connection TX power can only be set after the connection is established. After disconnecting, the corresponding TX power will not be affected. 
- ESP_BLE_PWR_TYPE_DEFAULTcan be used to set the TX power for power types that have not been set before. It will not affect the TX power values which have been set for the ADV/SCAN/CONN0-8 power types.
- If none of power type is set, the system will use - ESP_PWR_LVL_P3as default for all power types.
 - Values: - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL0
- TX power for connection handle 0 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL1
- TX power for connection handle 1 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL2
- TX power for connection handle 2 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL3
- TX power for connection handle 3 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL4
- TX power for connection handle 4 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL5
- TX power for connection handle 5 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL6
- TX power for connection handle 6 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL7
- TX power for connection handle 7 
 - 
enumerator ESP_BLE_PWR_TYPE_CONN_HDL8
- TX power for connection handle 8 
 - 
enumerator ESP_BLE_PWR_TYPE_ADV
- TX power for advertising 
 - 
enumerator ESP_BLE_PWR_TYPE_SCAN
- TX power for scan 
 - 
enumerator ESP_BLE_PWR_TYPE_DEFAULT
- Default TX power type, which can be used to set the TX power for power types that have not been set before. 
 - 
enumerator ESP_BLE_PWR_TYPE_NUM
- Number of types 
 
- 
enum esp_power_level_t
- Bluetooth TX power level (index). Each index corresponds to a specific power value in dBm. - Values: - 
enumerator ESP_PWR_LVL_N12
- Corresponding to -12 dBm 
 - 
enumerator ESP_PWR_LVL_N9
- Corresponding to -9 dBm 
 - 
enumerator ESP_PWR_LVL_N6
- Corresponding to -6 dBm 
 - 
enumerator ESP_PWR_LVL_N3
- Corresponding to -3 dBm 
 - 
enumerator ESP_PWR_LVL_N0
- Corresponding to 0 dBm 
 - 
enumerator ESP_PWR_LVL_P3
- Corresponding to +3 dBm 
 - 
enumerator ESP_PWR_LVL_P6
- Corresponding to +6 dBm 
 - 
enumerator ESP_PWR_LVL_P9
- Corresponding to +9 dBm 
 - 
enumerator ESP_PWR_LVL_N14
- Backward compatibility! Setting to -14 dBm will actually result in -12 dBm 
 - 
enumerator ESP_PWR_LVL_N11
- Backward compatibility! Setting to -11 dBm will actually result in -9 dBm 
 - 
enumerator ESP_PWR_LVL_N8
- Backward compatibility! Setting to -8 dBm will actually result in -6 dBm 
 - 
enumerator ESP_PWR_LVL_N5
- Backward compatibility! Setting to -5 dBm will actually result in -3 dBm 
 - 
enumerator ESP_PWR_LVL_N2
- Backward compatibility! Setting to -2 dBm will actually result in 0 dBm 
 - 
enumerator ESP_PWR_LVL_P1
- Backward compatibility! Setting to +1 dBm will actually result in +3 dBm 
 - 
enumerator ESP_PWR_LVL_P4
- Backward compatibility! Setting to +4 dBm will actually result in +6 dBm 
 - 
enumerator ESP_PWR_LVL_P7
- Backward compatibility! Setting to +7 dBm will actually result in +9 dBm 
 
- 
enumerator ESP_PWR_LVL_N12
HCI Vendor-specific (VS) Commands
Espressif's HCI VS commands are exclusively designed for use with Espressif's Bluetooth Host stack or internal debugging purposes. Application developers should not initialize or invoke these VS commands in their applications. Please refer to HCI Vendor-specific (VS) Commands for detailed information.