Bluetooth® Low Energy AT Commands

[中文]

Introduction

Currently, AT firmware for ESP32 series supports Bluetooth® Core Specification Version 4.2.

Important

The default AT firmware supports all the AT commands mentioned on this page. If you need to modify the commands supported by ESP32 by default, please compile the ESP-AT project by following the steps in Compile ESP-AT Project Locally documentation. In the project configuration during the fifth step, make the following selections (Each item below is independent. Choose it according to your needs):

  • Disable BluFi commands: Component config -> AT -> AT blufi command support

  • Disable Bluetooth LE commands: Component config -> AT -> AT ble command support

  • Disable Bluetooth LE HID commands: Component config -> AT -> AT ble hid command support

AT+BLEINIT: Bluetooth LE Initialization

Query Command

Function:

Check the initialization status of Bluetooth LE.

Command:

AT+BLEINIT?

Response:

If Bluetooth LE is initialized, AT will return:

+BLEINIT:<role>
OK

If Bluetooth LE is not initialized, AT will return:

+BLEINIT:0
OK

Set Command

Function:

Initialize the role of Bluetooth LE.

Command:

AT+BLEINIT=<init>

Response:

OK

Parameter

  • <init>:

  • 0: deinit Bluetooth LE

  • 1: client role

  • 2: server role

Notes

  • To achieve better performance, it is recommended to disable SoftAP by sending the AT+CWMODE=0/1 command before using Bluetooth LE function. For more details, please refer to the RF Coexistence documentation.

  • Before using other Bluetooth LE AT commands, you should run this command first to trigger the initialization process.

  • After the initialization, the Bluetooth LE role cannot be changed unless you run AT+RST to restart the system first and then re-initialize the Bluetooth LE role.

  • Before you deinitialize the Bluetooth stack, it is recommended to stop broadcasting, stop scanning, and disconnect all existing connections.

  • If Bluetooth LE is initialized, AT+CIPMODE cannot be set to 1.

Example

AT+BLEINIT=1

AT+BLEADDR: Query/Set Bluetooth LE Device Address

Query Command

Function:

Query the Bluetooth LE Public Address.

Command:

AT+BLEADDR?

Response:

+BLEADDR:<BLE_public_addr>
OK

Set Command

Function:

Set the Bluetooth LE address type.

Command:

AT+BLEADDR=<addr_type>[,<random_addr>]

Response:

OK

Parameter

  • <addr_type>:

  • 0: Public Address

  • 1: Random Address

Note

  • A Static Address should meet the following requirements:

  • The two most significant bits of the address should be equal to 1.

  • At least one bit of the random part of the address should be 0.

  • At least one bit of the random part of the address should be 1.

  • The configuration changes will be saved in the NVS area.

Example

AT+BLEADDR=1,"f8:7f:24:87:1c:7b"    // Set Random Device Address, Static Address
AT+BLEADDR=1                        // Set Random Device Address, Private Address
AT+BLEADDR=0                        // Set Public Device Address

AT+BLENAME: Query/Set Bluetooth LE Device Name

Query Command

Function:

Query the Bluetooth LE device name.

Command:

AT+BLENAME?

Response:

+BLENAME:<device_name>
OK

Set Command

Function:

Set the Bluetooth LE device name.

Command:

AT+BLENAME=<device_name>

Response:

OK

Parameter

  • <device_name>: the Bluetooth LE device name. The maximum length is 32. Default: “ESP-AT”.

Note

  • The configuration changes will be saved in the NVS area if AT+SYSSTORE=1.

  • After setting the device name with this command, it is recommended that you execute the AT+BLEADVDATA command to add the device name into the advertising data.

Example

AT+BLENAME="esp_demo"

AT+BLESCANPARAM: Query/Set Parameters of Bluetooth LE Scanning

Query Command

Function:

Query the parameters of Bluetooth LE scanning.

Command:

AT+BLESCANPARAM?

Response:

+BLESCANPARAM:<scan_type>,<own_addr_type>,<filter_policy>,<scan_interval>,<scan_window>
OK

Set Command

Function:

Set the parameters of Bluetooth LE scanning.

Command:

AT+BLESCANPARAM=<scan_type>,<own_addr_type>,<filter_policy>,<scan_interval>,<scan_window>

Response:

OK

Parameters

  • <scan_type>:

  • 0: passive scan

  • 1: active scan

  • <own_addr_type>:

  • 0: Public Address

  • 1: Random Address

  • 2: RPA Public Address

  • 3: RPA Random Address

  • <filter_policy>:

  • 0: BLE_SCAN_FILTER_ALLOW_ALL

  • 1: BLE_SCAN_FILTER_ALLOW_ONLY_WLST

  • 2: BLE_SCAN_FILTER_ALLOW_UND_RPA_DIR

  • 3: BLE_SCAN_FILTER_ALLOW_WLIST_PRA_DIR

  • <scan_interval>: scan interval. It should be more than or equal to the value of <scan_window>. The range of this parameter is [0x0004,0x4000]. The scan interval equals this parameter multiplied by 0.625 ms, so the range for the actual scan interval is [2.5,10240] ms.

  • <scan_window>: scan window. It should be less than or equal to the value of <scan_interval>. The range of this parameter is [0x0004,0x4000]. The scan window equals this parameter multiplied by 0.625 ms, so the range for the actual scan window is [2.5,10240] ms.

Example

AT+BLEINIT=1   // Role: client
AT+BLESCANPARAM=0,0,0,100,50

AT+BLESCAN: Enable Bluetooth LE Scanning

Set Command

Function:

Enable/disable scanning.

Command:

AT+BLESCAN=<enable>[,<duration>][,<filter_type>,<filter_param>]

Response:

+BLESCAN:<addr>,<rssi>,<adv_data>,<scan_rsp_data>,<addr_type>
OK
+BLESCANDONE

Parameters

  • <enable>:

  • 1: enable continuous scanning.

  • 0: disable continuous scanning.

  • [<duration>]: optional parameter. Unit: second.

  • If you want to disable the scanning, this parameter should be omitted.

  • If you want to enable the scanning, set a value for this parameter:

    • When you set it to 0, it means that scanning is continuous.

    • When set it to a value other than 0, for example, AT+BLESCAN=1,3, it means that scanning will last for 3 seconds and then stop automatically. The scanning results will be returned.

  • [<filter_type>]: filtering option.

  • 1: “MAC”.

  • 2: “NAME”.

  • <filter_param>: filtering parameter showing the remote device MAC address or remote device name.

  • <addr>: Bluetooth LE address.

  • <rssi>: signal strength.

  • <adv_data>: advertising data.

  • <scan_rsp_data>: scan response data.

  • <addr_type>: the address type of broadcasters.

Notes

  • The response OK does not necessarily come before the response +BLESCAN:<addr>,<rssi>,<adv_data>,<scan_rsp_data>,<addr_type>. It may be output before +BLESCAN:<addr>,<rssi>,<adv_data>,<scan_rsp_data>,<addr_type> or after it.

  • To obtain the scan response data, use the AT+BLESCANPARAM command to set the scan type to active scan (AT+BLESCANPARAM=1,0,0,100,50), and the peer device needs to set the scan_rsp_data.

Example

AT+BLEINIT=1    // Role: client
AT+BLESCAN=1    // start scanning
AT+BLESCAN=0    // stop scanning
AT+BLESCAN=1,3,1,"24:0A:C4:96:E6:88"  // start scanning, filter type is MAC address
AT+BLESCAN=1,3,2,"ESP-AT"  // start scanning, filter type is device name

AT+BLESCANRSPDATA: Set Bluetooth LE Scan Response

Set Command

Function:

Set scan response.

Command:

AT+BLESCANRSPDATA=<scan_rsp_data>

Response:

OK

Parameter

  • <scan_rsp_data>: scan response data is a HEX string. For example, if you want to set the response data to “0x11 0x22 0x33 0x44 0x55”, the command should be AT+BLESCANRSPDATA="1122334455".

Example

AT+BLEINIT=2   // Role: server
AT+BLESCANRSPDATA="1122334455"

AT+BLEADVPARAM: Query/Set Parameters of Bluetooth LE Advertising

Query Command

Function:

Query the parameters of advertising.

Command:

AT+BLEADVPARAM?

Response:

+BLEADVPARAM:<adv_int_min>,<adv_int_max>,<adv_type>,<own_addr_type>,<channel_map>,<adv_filter_policy>,<peer_addr_type>,<peer_addr>
OK

Set Command

Function:

Set the parameters of advertising.

Command:

AT+BLEADVPARAM=<adv_int_min>,<adv_int_max>,<adv_type>,<own_addr_type>,<channel_map>[,<adv_filter_policy>][,<peer_addr_type>,<peer_addr>]

Response:

OK

Parameters

  • <adv_int_min>: minimum advertising interval. The range of this parameter is [0x0020,0x4000]. The actual advertising interval equals this parameter multiplied by 0.625 ms, so the range for the actual minimum interval is [20, 10240] ms. It should be less than or equal to the value of <adv_int_max>.

  • <adv_int_max>: maximum advertising interval. The range of this parameter is [0x0020,0x4000]. The actual advertising interval equals this parameter multiplied by 0.625 ms, so the range for the actual maximum interval is [20, 10240] ms. It should be more than or equal to the value of <adv_int_min>.

  • <adv_type>:

  • 0: ADV_TYPE_IND

  • 1: ADV_TYPE_DIRECT_IND_HIGH

  • 2: ADV_TYPE_SCAN_IND

  • 3: ADV_TYPE_NONCONN_IND

  • 4: ADV_TYPE_DIRECT_IND_LOW

  • <own_addr_type>: own Bluetooth LE address type.

  • 0: BLE_ADDR_TYPE_PUBLIC

  • 1: BLE_ADDR_TYPE_RANDOM

  • <channel_map>: channel of advertising.

  • 1: ADV_CHNL_37

  • 2: ADV_CHNL_38

  • 4: ADV_CHNL_39

  • 7: ADV_CHNL_ALL

  • [<adv_filter_policy>]: filter policy of advertising.

  • 0: ADV_FILTER_ALLOW_SCAN_ANY_CON_ANY

  • 1: ADV_FILTER_ALLOW_SCAN_WLST_CON_ANY

  • 2: ADV_FILTER_ALLOW_SCAN_ANY_CON_WLST

  • 3: ADV_FILTER_ALLOW_SCAN_WLST_CON_WLST

  • [<peer_addr_type>]: remote Bluetooth LE address type.

  • 0: PUBLIC

  • 1: RANDOM

  • [<peer_addr>]: remote Bluetooth LE address.

Note

  • If peer_addr is not set, the query result will be all zero.

Example

AT+BLEINIT=2   // Role: server
AT+BLEADDR=1,"c2:34:45:78:66:89"
AT+BLEADVPARAM=50,50,0,1,4,0,1,"12:34:45:78:66:88"
// At this time, the MAC of the ESP device scanned by the BLE client is "c2:34:45:78:66:89".

AT+BLEADVDATA: Set Bluetooth LE Advertising Data

Set Command

Function:

Set advertising data.

Command:

AT+BLEADVDATA=<adv_data>

Response:

OK

Parameter

  • <adv_data>: advertising data in HEX string. For example, to set the advertising data to “0x11 0x22 0x33 0x44 0x55”, the command should be AT+BLEADVDATA="1122334455". The maximum length is 31 bytes.

Note

  • If advertising data is preset by command AT+BLEADVDATAEX=<dev_name>,<uuid>,<manufacturer_data>,<include_power>, it will be overwritten by this command.

  • If you run this command to modify the device name, it is recommended to also execute the AT+BLENAME command to set the same device name afterwards.

  • If the advertising data exceeds the maximum limit of this command, use command AT+BLESCANRSPDATA.

Example

AT+BLEINIT=2   // Role: server
AT+BLEADVDATA="1122334455"

AT+BLEADVDATAEX: Automatically Set Bluetooth LE Advertising Data

Query Command

Function:

Query the parameters of advertising data.

Command:

AT+BLEADVDATAEX?

Response:

+BLEADVDATAEX:<dev_name>,<uuid>,<manufacturer_data>,<include_power>

OK

Set Command

Function:

Set the advertising data and start advertising.

Command:

AT+BLEADVDATAEX=<dev_name>,<uuid>,<manufacturer_data>,<include_power>

Response:

OK

Parameters

  • <dev_name>: string parameter showing a device name. For example, if you want to set the device name to “just-test”, the command should be AT+BLEADVSTARTEX="just-test",<uuid>,<manufacturer_data>,<include_power>.

  • <uuid>: string parameter. For example, if you want to set the UUID to “0xA002”, the command should be AT+BLEADVSTARTEX=<dev_name>,"A002",<manufacturer_data>,<include_power>.

  • <manufacturer_data>: manufacturer data in HEX string. For example, if you set the manufacturer data to “0x11 0x22 0x33 0x44 0x55”, the command should be AT+BLEADVSTARTEX=<dev_name>,<uuid>,"1122334455",<include_power>.

  • <include_power>: If you need to include the TX power in the advertising data, you should set the parameter to 1. Otherwise, set it to 0.

Note

  • If advertising data is preset by command AT+BLEADVDATA=<adv_data>, it will be overwritten by this command.

  • This command automatically changes the adv type previously set using AT+BLEADVPARAM to 0.

Example

AT+BLEINIT=2   // Role: server
AT+BLEADVDATAEX="ESP-AT","A002","0102030405",1

AT+BLEADVSTART: Start Bluetooth LE Advertising

Execute Command

Function:

Start advertising.

Command:

AT+BLEADVSTART

Response:

OK

Notes

  • If advertising parameters are NOT set by command AT+BLEADVPARAM=<adv_parameter>, the default parameters will be used.

  • If advertising data is NOT set by command AT+BLEADVDATA=<adv_data>, the advertising playload will be empty.

  • If advertising data is preset by command AT+BLEADVDATA=<adv_data>, it will be overwritten by AT+BLEADVDATAEX=<dev_name>,<uuid>,<manufacturer_data>,<include_power> and vice versa.

  • After the start of Bluetooth LE advertisement, if no connection is established, the advertisement will keep going on; if a connection is established, the advertisement will automatically end.

Example

AT+BLEINIT=2   // Role: server
AT+BLEADVSTART

AT+BLEADVSTOP: Stop Bluetooth LE Advertising

Execute Command

Function:

Stop advertising.

Command:

AT+BLEADVSTOP

Response:

OK

Note

  • After the start of advertising, if the Bluetooth LE connection is established successfully, it will stop advertising automatically. In such a case, this command does NOT need to be called.

Example

AT+BLEINIT=2   // Role: server
AT+BLEADVSTART
AT+BLEADVSTOP

AT+BLECONN: Establish Bluetooth LE Connection

Query Command

Function:

Query the Bluetooth LE connection.

Command:

AT+BLECONN?

Response:

+BLECONN:<conn_index>,<remote_address>
OK

If the connection has not been established, there will be no <conn_index> and <remote_address> in the response.

Set Command

Function:

Establish the Bluetooth LE connection.

Command:

AT+BLECONN=<conn_index>,<remote_address>[,<addr_type>,<timeout>]

Response:

If the connection is established successfully, it will prompt:

+BLECONN:<conn_index>,<remote_address>

OK

If the connection fails, it will prompt:

+BLECONN:<conn_index>,-1

ERROR

If the connection fails due to parameters error or other reasons, it will prompt:

ERROR

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <remote_address>: remote Bluetooth LE address.

  • [<addr_type>]: the address type of broadcasters:

    • 0: Public Address

    • 1: Random Address

  • [<timeout>]: the timeout for the connection command. Unit: second. Range: [3,30].

Notes

  • It is recommended to scan devices by running AT+BLESCAN before initiating a new connection to ensure that the target device is in the broadcast state.

  • The maximum timeout for connection is 30 seconds.

  • If the Bluetooth LE server is initialized and the connection is established successfully, you can use this command to discover the services in the peer device (GATTC). The following GATTC commands can also be used:

  • AT+BLEGATTCPRIMSRV

  • AT+BLEGATTCINCLSRV

  • AT+BLEGATTCCHAR

  • AT+BLEGATTCRD

  • AT+BLEGATTCWR

  • AT+BLEGATTSIND

  • If the AT+BLECONN? is executed when the Bluetooth LE is not initialized (AT+BLEINIT=0), the system will not output +BLECONN:<conn_index>,<remote_address> .

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:0a:c4:09:34:23",0,10

AT+BLECONNPARAM: Query/Update Parameters of Bluetooth LE Connection

Query Command

Function:

Query the parameters of Bluetooth LE connection.

Command:

AT+BLECONNPARAM?

Response:

+BLECONNPARAM:<conn_index>,<min_interval>,<max_interval>,<cur_interval>,<latency>,<timeout>
OK

Set Command

Function:

Update the parameters of Bluetooth LE connection.

Command:

AT+BLECONNPARAM=<conn_index>,<min_interval>,<max_interval>,<latency>,<timeout>

Response:

OK

If the setting fails, it will prompt the message below:

+BLECONNPARAM: <conn_index>,-1

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <min_interval>: minimum connecting interval. It should be less than or equal to the value of <max_interval>. The range of this parameter is [0x0006,0x0C80]. The actual connecting interval equals this parameter multiplied by 1.25 ms, so the range for the actual minimum interval is [7.5,4000] ms.

  • <max_interval>: maximum connecting interval. It should be more than or equal to the value of <min_interval>. The range of this parameter is [0x0006,0x0C80]. The actual connecting interval equals this parameter multiplied by 1.25 ms, so the range for the actual maximum interval is [7.5,4000] ms.

  • <cur_interval>: current connecting interval.

  • <latency>: latency. Range: [0x0000,0x01F3].

  • <timeout>: timeout. The range of this parameter is [0x000A,0x0C80]. The actual timeout equals this parameter multiplied by 10 ms, so the range for the actual timeout is [100,32000] ms.

Note

  • This command supports client or server roles when updating its connection parameters. Of course, the connection has to be established first.

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:0a:c4:09:34:23"
AT+BLECONNPARAM=0,12,14,1,500

AT+BLEDISCONN: End Bluetooth LE Connection

Execute Command

Function:

End the Bluetooth LE connection.

Command:

AT+BLEDISCONN=<conn_index>

Response:

OK  // The AT+BLEDISCONN command is received.
+BLEDISCONN:<conn_index>,<remote_address>  // The command is successful.

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <remote_address>: remote Bluetooth LE address.

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:0a:c4:09:34:23"
AT+BLEDISCONN=0

AT+BLEDATALEN: Set Bluetooth LE Data Packet Length

Set Command

Function:

Set the length of Bluetooth LE data packet.

Command:

AT+BLEDATALEN=<conn_index>,<pkt_data_len>

Response:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <pkt_data_len>: data packet’s length. Range: [0x001B,0x00FB].

Note

  • The Bluetooth LE connection has to be established first.

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:0a:c4:09:34:23"
AT+BLEDATALEN=0,30

AT+BLECFGMTU: Set Bluetooth LE MTU Length

Query Command

Function:

Query the length of the maximum transmission unit (MTU).

Command:

AT+BLECFGMTU?

Response:

+BLECFGMTU:<conn_index>,<mtu_size>
OK

Set Command

Function:

Set the length of the maximum transmission unit (MTU).

Command:

AT+BLECFGMTU=<conn_index>,<mtu_size>

Response:

OK  // The command is received.

Parameters

-  **<conn_index>**: index of Bluetooth LE connection. Range: [0,2].
-  **<mtu_size>**: MTU length. Unit: byte. Range: [23,517].

Notes

-  Bluetooth LE connection has to be established first.
-  Only the client can call this command to set the length of MTU.
-  The actual length of MTU needs to be negotiated. The ``OK`` response only indicates an attempt to negotiate the length. The actual length may not be the value you set. Therefore, it is recommended to run command :ref:`AT+BLECFGMTU? <cmd-BMTU>` to query the actual length.

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:0a:c4:09:34:23"
AT+BLECFGMTU=0,300

AT+BLEGATTSSRVCRE: GATTS Creates Services

Execute Command

Function:

The Generic Attributes Server (GATTS) creates Bluetooth LE services.

Command:

AT+BLEGATTSSRVCRE

Response:

OK

Notes

  • If you are using an ESP32 as a Bluetooth LE server, the mfg_nvs.bin with GATTS configuration should be downloaded into flash in order to provide services.

  • This command should be called immediately to create services, right after the Bluetooth LE server is initialized; If a Bluetooth LE connection is established first, the service creation will fail.

  • If the Bluetooth LE client is initialized, you can use this command to create local services. Some GATTS commands can also be used, such as those to start and stop services, set attribute values, and send notifications/indications. See the list below for the specific commands.

Example

AT+BLEINIT=2   // Role: server
AT+BLEGATTSSRVCRE

AT+BLEGATTSSRVSTART: GATTS Starts Services

Execute Command

Function:

GATTS starts all services.

Command:

AT+BLEGATTSSRVSTART

Set Command

Function:

GATTS starts a specific service.

Command:

AT+BLEGATTSSRVSTART=<srv_index>

Response:

OK

Parameter

  • <srv_index>: service’s index starting from 1.

Example

AT+BLEINIT=2   // Role: server
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRVSTART

AT+BLEGATTSSRVSTOP: GATTS Stops Services

Execute Command

Function:

GATTS stops all services.

Command:

AT+BLEGATTSSRVSTOP

Set Command

Function:

GATTS stops a specific service.

Command:

AT+BLEGATTSSRVSTOP=<srv_index>

Response:

OK

Parameter

  • <srv_index>: service’s index starting from 1.

Example

AT+BLEINIT=2   // Role: server
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRVSTART
AT+BLEGATTSSRVSTOP

AT+BLEGATTSSRV: GATTS Discovers Services

Query Command

Function:

GATTS discovers services.

Command:

AT+BLEGATTSSRV?

Response:

+BLEGATTSSRV:<srv_index>,<start>,<srv_uuid>,<srv_type>
OK

Parameters

  • <srv_index>: service’s index starting from 1.

  • <start>:

  • 0: the service has not started.

  • 1: the service has already started.

  • <srv_uuid>: service’s UUID.

  • <srv_type>: service’s type.

  • 0: not primary service.

  • 1: primary service.

Example

AT+BLEINIT=2   // Role: server
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRV?

AT+BLEGATTSCHAR: GATTS Discovers Characteristics

Query Command

Function:

GATTS discovers characteristics.

Command:

AT+BLEGATTSCHAR?

Response:

The response for a characteristic:

+BLEGATTSCHAR:"char",<srv_index>,<char_index>,<char_uuid>,<char_prop>

The response for a descriptor:

+BLEGATTSCHAR:"desc",<srv_index>,<char_index>,<desc_index>
OK

Parameters

  • <srv_index>: service’s index starting from 1.

  • <char_index>: characteristic’s index starting from 1.

  • <char_uuid>: characteristic’s UUID.

  • <char_prop>: characteristic’s properties.

  • <desc_index>: descriptor’s index.

  • <desc_uuid>: descriptor’s UUID.

Example

AT+BLEINIT=2   // Role: server
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRVSTART
AT+BLEGATTSCHAR?

AT+BLEGATTSNTFY: Notify a Client of the Value of a Characteristic Value from the Server

Set Command

Function:

Notify a client of the value of a characteristic value from the server.

Command:

AT+BLEGATTSNTFY=<conn_index>,<srv_index>,<char_index>,<length>

Response:

>

The symbol > indicates that AT is ready for receiving serial data, and you can enter data now. When the requirement of data length determined by the parameter <length> is met, the notification starts.

If the data transmission is successful, AT returns:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <srv_index>: service’s index. It can be queried with command AT+BLEGATTSCHAR?.

  • <char_index>: characteristic’s index. It can be queried with command AT+BLEGATTSCHAR?.

  • <length>: data length. The maximum length is ( :ref:`MTU <cmd-BMTU>` - 3).

Example

AT+BLEINIT=2      // Role: server.
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRVSTART
AT+BLEADVSTART    // Start advertising. After the client is connected, it must be configured to receive notifications.
AT+BLEGATTSCHAR?  // Query the characteristics which the client will be notified of.
// For example, to notify of 4-byte data using the 6th characteristic in the 3rd service, use the following command:
AT+BLEGATTSNTFY=0,3,6,4
// After the symbol ">" shows, enter the 4-byte data, such as "1234". Then the data will be transmitted automatically.

AT+BLEGATTSIND: Indicate the Characteristic Value from the Server to a Client

Set Command

Function:

Indicate the characteristic value from the server to a client.

Command:

AT+BLEGATTSIND=<conn_index>,<srv_index>,<char_index>,<length>

Response:

>

The symbol > indicates that AT is ready for receiving serial data and you can enter data now. When the requirement of data length determined by the parameter <length> is met, the indication starts.

If the data transmission is successful, AT returns:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <srv_index>: service’s index. It can be queried with command AT+BLEGATTSCHAR?.

  • <char_index>: characteristic’s index; it can be fetched with command AT+BLEGATTSCHAR?.

  • <length>: data length. The maximum length is (MTU - 3).

Example

AT+BLEINIT=2      // Role: server
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRVSTART
AT+BLEADVSTART    // Start advertising. After the client is connected, it must be configured to receive indications.
AT+BLEGATTSCHAR?  // Query the characteristics which the client can receive indications.
// For example, to indicate 4 bytes of data using the 7th characteristic in the 3rd service, use the following command:
AT+BLEGATTSIND=0,3,7,4
// After the symbol ">" shows, input 4 bytes of data, such as "1234". Then the data will be transmitted automatically.

AT+BLEGATTSSETATTR: GATTS Sets Characteristics

Set Command

Function:

GATTS sets its characteristic (descriptor).

Command:

AT+BLEGATTSSETATTR=<srv_index>,<char_index>,[<desc_index>],<length>

Response:

>

The symbol > indicates that AT is ready for receiving serial data and you can enter data now. When the requirement of data length determined by the parameter <length> is met, the setting starts.

If the setting is successful, AT returns:

OK

Parameters

  • <srv_index>: service’s index. It can be queried with command AT+BLEGATTSCHAR?.

  • <char_index>: characteristic’s index; it can be fetched with command AT+BLEGATTSCHAR?.

  • If it is set, this command is used to set the value of the descriptor.

  • Otherwise, this command is used to set the value of the characteristic.

  • <length>: data length.

Note

  • If the value of <length> is larger than the maximum length allowed, the setting will fail. The service table is defined in gatts_data.csv .

Example

AT+BLEINIT=2   // Role: server.
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRVSTART
AT+BLEGATTSCHAR?
// For example, to set 1 byte of data of the 1st characteristic in the 1st service, use the following command:
AT+BLEGATTSSETATTR=1,1,,1
// After the symbol ">" shows, input 1 byte of data, such as "8". Then the setting starts.

AT+BLEGATTCPRIMSRV: GATTC Discovers Primary Services

Query Command

Function:

Generic Attributes Client (GATTC) discovers primary services.

Command:

AT+BLEGATTCPRIMSRV=<conn_index>

Response:

+BLEGATTCPRIMSRV:<conn_index>,<srv_index>,<srv_uuid>,<srv_type>
OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <srv_index>: service’s index starting from 1.

  • <srv_uuid>: service’s UUID.

  • <srv_type>: service’s type.

  • 0: not primary service.

  • 1: primary service.

Note

  • The Bluetooth LE connection has to be established first.

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:12:5f:9d:91:98"
AT+BLEGATTCPRIMSRV=0

AT+BLEGATTCINCLSRV: GATTC Discovers Included Services

Set Command

Function:

GATTC discovers included services.

Command:

AT+BLEGATTCINCLSRV=<conn_index>,<srv_index>

Response:

+BLEGATTCINCLSRV:<conn_index>,<srv_index>,<srv_uuid>,<srv_type>,<included_srv_uuid>,<included_srv_type>
OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <srv_index>: service’s index. It can be queried with command AT+BLEGATTCPRIMSRV=<conn_index>.

  • <srv_uuid>: service’s UUID.

  • <srv_type>: service’s type.

  • 0: not primary service.

  • 1: primary service.

  • <included_srv_uuid>: included service’s UUID.

  • <included_srv_type>: included service’s type.

  • 0: not primary service.

  • 1: primary service.

Note

  • The Bluetooth LE connection has to be established first.

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:12:5f:9d:91:98"
AT+BLEGATTCPRIMSRV=0
AT+BLEGATTCINCLSRV=0,1  // set a specific index according to the result of the previous command

AT+BLEGATTCCHAR: GATTC Discovers Characteristics

Set Command

Function:

GATTC discovers characteristics.

Command:

AT+BLEGATTCCHAR=<conn_index>,<srv_index>

Response:

The response for a characteristic:

+BLEGATTCCHAR:"char",<conn_index>,<srv_index>,<char_index>,<char_uuid>,<char_prop>

The response for a descriptor:

+BLEGATTCCHAR:"desc",<conn_index>,<srv_index>,<char_index>,<desc_index>,<desc_uuid>
OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <srv_index>: service’s index. It can be queried with command AT+BLEGATTCPRIMSRV=<conn_index>.

  • <char_index>: characteristic’s index starting from 1.

  • <char_uuid>: characteristic’s UUID.

  • <char_prop>: characteristic’s properties.

  • <desc_index>: descriptor’s index.

  • <desc_uuid>: descriptor’s UUID.

Note

  • The Bluetooth LE connection has to be established first.

Example

AT+BLEINIT=1   // Role: client
AT+BLECONN=0,"24:12:5f:9d:91:98"
AT+BLEGATTCPRIMSRV=0
AT+BLEGATTCCHAR=0,1 // set a specific index according to the result of the previous command

AT+BLEGATTCRD: GATTC Reads Characteristics

Set Command

Function:

GATTC reads a characteristic or descriptor.

Command:

AT+BLEGATTCRD=<conn_index>,<srv_index>,<char_index>[,<desc_index>]

Response:

+BLEGATTCRD:<conn_index>,<len>,<value>
OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <srv_index>: service’s index. It can be queried with command AT+BLEGATTCPRIMSRV=<conn_index>.

  • <char_index>: characteristic’s index; it can be fetched with command AT+BLEGATTCCHAR=<conn_index>,<srv_index>.

  • [<desc_index>]: descriptor’s index.

  • If it is set, the value of the target descriptor will be read.

  • if it is not set, the value of the target characteristic will be read.

  • <len>: data length.

  • <value>: <char_value> or <desc_value>.

  • <char_value>: characteristic’s value. String format is read by command AT+BLEGATTCRD=<conn_index>,<srv_index>,<char_index>. For example, if the response is +BLEGATTCRD:0,1,0, it means that the value length is 1, and the content is “0”.

  • <desc_value>: descriptor’s value. String format is read by command AT+BLEGATTCRD=<conn_index>,<srv_index>,<char_index>,<desc_index>. For example, if the response is +BLEGATTCRD:0,4,0123, it means that the value length is 4, and the content is “0123”.

Notes

  • The Bluetooth LE connection has to be established first.

  • If the target characteristic cannot be read, it will return “ERROR”.

Example

AT+BLEINIT=1   // Role: client.
AT+BLECONN=0,"24:12:5f:9d:91:98"
AT+BLEGATTCPRIMSRV=0
AT+BLEGATTCCHAR=0,3 // Set a specific index according to the result of the previous command.
// For example, to read 1st descriptor of the 2nd characteristic in the 3rd service, use the following command:
AT+BLEGATTCRD=0,3,2,1

AT+BLEGATTCWR: GATTC Writes Characteristics

Set Command

Function:

GATTC writes characteristics or descriptors.

Command:

AT+BLEGATTCWR=<conn_index>,<srv_index>,<char_index>[,<desc_index>],<length>

Response:

>

The symbol > indicates that AT is ready for receiving serial data and you can enter data now. When the requirement of data length determined by the parameter <length> is met, the writing starts.

If the setting is successful, AT returns:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <srv_index>: service’s index. It can be queried with command AT+BLEGATTCPRIMSRV=<conn_index>.

  • <char_index>: characteristic’s index; it can be fetched with command AT+BLEGATTCCHAR=<conn_index>,<srv_index>.

  • [<desc_index>]: descriptor’s index.

  • If it is set, the value of the target descriptor will be written.

  • If it is not set, the value of the target characteristic will be written.

  • <length>: data length. The value range of this parameter is subject to gatts_data.csv in val_max_len parameter.

Notes

  • The Bluetooth LE connection has to be established first.

  • If the target characteristic cannot be written, it will return “ERROR”.

Example

AT+BLEINIT=1   // Role: client.
AT+BLECONN=0,"24:12:5f:9d:91:98"
AT+BLEGATTCPRIMSRV=0
AT+BLEGATTCCHAR=0,3 // Set a specific index according to the result of the previous command.
// For example, to write 6 bytes of data to the 4th characteristic in the 3rd service, use the following command:
AT+BLEGATTCWR=0,3,4,,6
// After the symbol ">" shows, input 6 bytes of data, such as "123456". Then the writing starts.

AT+BLESPPCFG: Query/Set Bluetooth LE SPP Parameters

Query Command

Function:

Query the parameters of Bluetooth LE Serial Port Profile (SPP).

Command:

AT+BLESPPCFG?

Response:

+BLESPPCFG:<tx_service_index>,<tx_char_index>,<rx_service_index>,<rx_char_index>,<auto_conn>
OK

Set Command

Function:

Set or reset the parameters of Bluetooth LE SPP.

Command:

AT+BLESPPCFG=<cfg_enable>[,<tx_service_index>,<tx_char_index>,<rx_service_index>,<rx_char_index>][,<auto_conn>]

Response:

OK

Parameters

  • <cfg_enable>:

  • 0: all the SPP parameters will be reset, and the following parameters do not need input.

  • 1: you should input the following parameters.

  • <tx_service_index>: tx service’s index. It can be queried with command AT+BLEGATTCPRIMSRV=<conn_index> and AT+BLEGATTSSRV?.

  • <tx_char_index>: tx characteristic’s index. It can be queried with command AT+BLEGATTCCHAR=<conn_index>,<srv_index> and AT+BLEGATTSCHAR?.

  • <rx_service_index>: rx service’s index. It can be queried with command AT+BLEGATTCPRIMSRV=<conn_index> and AT+BLEGATTSSRV?.

  • <rx_char_index>: rx characteristic’s index. It can be queried with command AT+BLEGATTCCHAR=<conn_index>,<srv_index> and AT+BLEGATTSCHAR?.

  • <auto_conn>: Bluetooth LE SPP auto-reconnection flag. By default, automatic reconnection is enabled.

  • 0: disable Bluetooth LE SPP automatic reconnection.

  • 1: enable Bluetooth LE SPP automatic reconnection

Notes

  • In Bluetooth LE client, the property of tx characteristic must be write with response or write without response, and the property of rx characteristic must be indicate or notify.

  • In Bluetooth LE server, the property of tx characteristic must be indicate or notify, and the property of rx characteristic must be write with response or write without response.

  • If the automatic reconnection function is disabled, when the connection is disconnected, a disconnection message is displayed (depending on AT+SYSMSG), you need to send the connection command again; If this function is enabled, the connection will be automatically reconnected after disconnection, and the MCU side will not be aware of the disconnection. If the MAC of the peer end changes, the connection will fail.

Example

AT+BLESPPCFG=0          // reset Bluetooth LE SPP parameters
AT+BLESPPCFG=1,3,5,3,7  // set Bluetooth LE SPP parameters
AT+BLESPPCFG?           // query Bluetooth LE SPP parameters

AT+BLESPP: Enter Bluetooth LE SPP Mode

Execute Command

Function:

Enter Bluetooth LE SPP mode.

Command:

AT+BLESPP

Response:

OK

>

This response indicates that AT has entered Bluetooth LE SPP mode and can send and receive data.

If the Bluetooth LE SPP status is wrong ( Notifications are not enabled at the opposite end after the Bluetooth LE connection is established ), the system returns:

ERROR

Notes

  • During the SPP transmission, AT will not prompt any exit the Bluetooth LE SPP passthrough mode information unless Bit0 of AT+SYSMSG is 1.

  • During the SPP transmission, AT will not prompt any connection status changes unless Bit2 of AT+SYSMSG is 1.

  • When the packet which only contains +++ is received, the device returns to normal command mode. Please wait for at least one second before sending the next AT command.

Example

AT+BLESPP   // enter Bluetooth LE SPP mode

AT+BLESECPARAM: Query/Set Bluetooth LE Encryption Parameters

Query Command

Function:

Query the parameters of Bluetooth LE SMP.

Command:

AT+BLESECPARAM?

Response:

+BLESECPARAM:<auth_req>,<iocap>,<enc_key_size>,<init_key>,<rsp_key>,<auth_option>
OK

Set Command

Function:

Set the parameters of Bluetooth LE SMP.

Command:

AT+BLESECPARAM=<auth_req>,<iocap>,<enc_key_size>,<init_key>,<rsp_key>[,<auth_option>]

Response:

OK

Parameters

  • <auth_req>: authentication request.

  • 0: NO_BOND

  • 1: BOND

  • 4: MITM

  • 8: SC_ONLY

  • 9: SC_BOND

  • 12: SC_MITM

  • 13: SC_MITM_BOND

  • <iocap>: input and output capability.

  • 0: DisplayOnly

  • 1: DisplayYesNo

  • 2: KeyboardOnly

  • 3: NoInputNoOutput

  • 4: Keyboard display

  • <enc_key_size>: encryption key size. Range: [7,16]. Unit: byte.

  • <init_key>: initial key represented in bit combinations.

  • <rsp_key>: response key represented in bit combinations.

  • <auth_option>: authentication option of security.

  • 0: Select the security level automatically.

  • 1: If it cannot follow the preset security level, the connection will disconnect.

Note

  • The bit pattern for parameters <init_key> and <rsp_key> is:

  • Bit0: Used to exchange the encryption key in the init key & response key.

  • Bit1: Used to exchange the IRK key in the init key & response key.

  • Bit2: Used to exchange the CSRK key in the init key & response key.

  • Bit3: Used to exchange the link key (only used in the Bluetooth LE & BR/EDR coexist mode) in the init key & response key.

Example

AT+BLESECPARAM=1,4,16,3,3,0

AT+BLEENC: Initiate Bluetooth LE Encryption Request

Set Command

Function:

Start a pairing request

Command:

AT+BLEENC=<conn_index>,<sec_act>

Response:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <sec_act>:

  • 0: SEC_NONE

  • 1: SEC_ENCRYPT

  • 2: SEC_ENCRYPT_NO_MITM

  • 3: SEC_ENCRYPT_MITM

Note

  • Before running this command, please set the security parameters and connection with remote devices.

Example

AT+RESTORE
AT+BLEINIT=2
AT+BLEGATTSSRVCRE
AT+BLEGATTSSRVSTART
AT+BLEADDR?
AT+BLESECPARAM=1,0,16,3,3
AT+BLESETKEY=123456
AT+BLEADVSTART
// Use your Bluetooth LE debugging app as a client to establish a Bluetooth LE connection with the ESP32
AT+BLEENC=0,3

AT+BLEENCRSP: Respond to the Pairing Request from the Peer Device

Set Command

Function:

Respond to the pairing request from the peer device.

Command:

AT+BLEENCRSP=<conn_index>,<accept>

Response:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <accept>:

  • 0: reject

  • 1: accept

Note

  • After running this command, AT will output the pairing result at the end of the pairing process.

+BLEAUTHCMPL:<conn_index>,<enc_result>

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <enc_result>:

  • 0: encryption succeeded

  • 1: encryption failed

Example

AT+BLEENCRSP=0,1

AT+BLEKEYREPLY: Reply the Key Value to the Peer Device

Set Command

Function:

Reply a pairing key.

Command:

AT+BLEKEYREPLY=<conn_index>,<key>

Response:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <key>: pairing key.

Example

AT+BLEKEYREPLY=0,649784

AT+BLECONFREPLY: Reply the Confirm Value to the Peer Device in the Legacy Connection Stage

Set Command

Function:

Reply a pairing result.

Command:

AT+BLECONFREPLY=<conn_index>,<confirm>

Response:

OK

Parameters

  • <conn_index>: index of Bluetooth LE connection. Range: [0,2].

  • <confirm>:

  • 0: No

  • 1: Yes

Example

AT+BLECONFREPLY=0,1

AT+BLEENCDEV: Query Bonded Bluetooth LE Encryption Device List

Query Command

Function:

Query bonded Bluetooth LE encryption device list.

Command:

AT+BLEENCDEV?

Response:

+BLEENCDEV:<enc_dev_index>,<mac_address>
OK

Parameters

  • <enc_dev_index>: index of the bonded devices. This parameter is not necessarily equal to the conn_index parameter in the Bluetooth LE connection list queried by the command AT+BLECONN. Range: [0,14].

  • <mac_address>: MAC address.

Note

  • ESP-AT allows a maximum of 15 devices to be bonded. If the number of bonded devices exceeds 15, the newly bonded device information will sequentially (from 0 to 14) overwrite the previous device information according to the binding order.

Example

AT+BLEENCDEV?

AT+BLEENCCLEAR: Clear Bluetooth LE Encryption Device List

Set Command

Function:

Remove a device from the security database list with a specific index.

Command:

AT+BLEENCCLEAR=<enc_dev_index>

Response:

OK

Execute Command

Function:

Remove all devices from the security database.

Command:

AT+BLEENCCLEAR

Response:

OK

Parameter

  • <enc_dev_index>: index of the bonded devices.

Example

AT+BLEENCCLEAR

AT+BLESETKEY: Set Bluetooth LE Static Pair Key

Query Command

Function:

Query the Bluetooth LE static pair key. If it is not set, AT will return -1.

Command:

AT+BLESETKEY?

Response:

+BLESETKEY:<static_key>
OK

Set Command

Function:

Set a Bluetooth LE static pair key for all Bluetooth LE connections.

Command:

AT+BLESETKEY=<static_key>

Response:

OK

Parameter

  • <static_key>: static Bluetooth LE pair key.

Example

AT+BLESETKEY=123456

AT+BLEHIDINIT: Bluetooth LE HID Profile Initialization

Query Command

Function:

Query the initialization status of Bluetooth LE HID profile.

Command:

AT+BLEHIDINIT?

Response:

If Bluetooth LE HID device profile is not initialized, AT will return:

+BLEHIDINIT:0
OK

If Bluetooth LE HID device profile is initialized, AT will return:

+BLEHIDINIT:1
OK

Set Command

Function:

Initialize the Bluetooth LE HID profile.

Command:

AT+BLEHIDINIT=<init>

Response:

OK

Parameter

  • <init>:

  • 0: deinit Bluetooth LE HID profile

  • 1: init Bluetooth LE HID profile

Note

  • The Bluetooth LE HID command cannot be used at the same time with general GATT/GAP commands.

Example

AT+BLEHIDINIT=1

AT+BLEHIDKB: Send Bluetooth LE HID Keyboard Information

Set Command

Function:

Send keyboard information.

Command:

AT+BLEHIDKB=<Modifier_keys>,<key_1>,<key_2>,<key_3>,<key_4>,<key_5>,<key_6>

Response:

OK

Parameters

  • <Modifier_keys>: modifier keys mask

  • <key_1>: key code 1

  • <key_2>: key code 2

  • <key_3>: key code 3

  • <key_4>: key code 4

  • <key_5>: key code 5

  • <key_6>: key code 6

Note

  • For more information about key codes, please refer to the chapter Keyboard/Keypad Page of Universal Serial Bus HID Usage Tables.

  • To use this command to interact with iOS products, your devices need to pass MFI certification first.

Example

AT+BLEHIDKB=0,4,0,0,0,0,0   // input the string "a"

AT+BLEHIDMUS: Send Bluetooth LE HID Mouse Information

Set Command

Function:

Send mouse information.

Command:

AT+BLEHIDMUS=<buttons>,<X_displacement>,<Y_displacement>,<wheel>

Response:

OK

Parameters

  • <buttons>: mouse button

  • <X_displacement>: X displacement

  • <Y_displacement>: Y displacement

  • <wheel>: wheel

Note

  • For more information about HID mouse, please refer to the section Generic Desktop Page, and Application Usages of Universal Serial Bus HID Usage Tables.

  • To use this command to interact with iOS products, your devices need to pass MFI certification first.

Example

AT+BLEHIDMUS=0,10,10,0

AT+BLEHIDCONSUMER: Send Bluetooth LE HID Consumer Information

Set Command

Function:

Send consumer information.

Command:

AT+BLEHIDCONSUMER=<consumer_usage_id>

Response:

OK

Parameter

Note

  • To use this command to interact with iOS products, your devices need to pass MFI certification first.

Example

AT+BLEHIDCONSUMER=233   // volume up

AT+BLUFI: Start or Stop BluFi

Query Command

Function:

Query the status of BluFi.

Command:

AT+BLUFI?

Response:

If BluFi is not started, it will return:

+BLUFI:0

OK

If BluFi is started, it will return:

+BLUFI:1

OK

Set Command

Function:

Start or stop BluFi.

Command:

AT+BLUFI=<option>[,<auth floor>]

Response:

OK

Parameter

  • <option>:

    • 0: stop BluFi

    • 1: start BluFi

  • <auth floor>: Wi-Fi authentication mode floor. ESP-AT will not connect to the AP whose authmode is lower than this floor.

    • 0: OPEN (Default)

    • 1: WEP

    • 2: WPA_PSK

    • 3: WPA2_PSK

    • 4: WPA_WPA2_PSK

    • 5: WPA2_ENTERPRISE

    • 6: WPA3_PSK

    • 7: WPA2_WPA3_PSK

Note

  • You can only start or stop BluFi when Bluetooth LE is not initialized (AT+BLEINIT=0).

  • To achieve better performance, it is recommended to disable SoftAP by sending the AT+CWMODE=0/1 command before using BluFi function. For more details, please refer to the RF Coexistence documentation.

  • After BluFi network configuration is completed, please send the AT+BLUFI=0 command to disable BluFi and release resources.

Example

AT+BLUFI=1

AT+BLUFINAME: Query/Set BluFi Device Name

Query Command

Function:

Query the BluFi name.

Command:

AT+BLUFINAME?

Response:

+BLUFINAME:<device_name>
OK

Set Command

Function:

Set the BluFi device name.

Command:

AT+BLUFINAME=<device_name>

Response:

OK

Parameter

  • <device_name>: the name of BluFi device.

Notes

  • If you need to set BluFi name, please set it before command AT+BLUFI=1. Otherwise, it will use the default name BLUFI_DEVICE.

  • The maximum length of BluFi name is 26 bytes.

  • The Blufi APP can be downloaded from the app store.

Example

AT+BLUFINAME="BLUFI_DEV"
AT+BLUFINAME?

AT+BLUFISEND: Send User-Customized Data over BluFi

Set Command

Function:

Send user-customized data from the ESP side to a phone over BluFi.

Command:

AT+BLUFISEND=<length>

Response:

>

The symbol > indicates that AT is ready for receiving serial data and you can enter data now. When the requirement of data length determined by the parameter <length> is met, the transmission starts.

If the data transmission is successful, AT returns:

OK

Parameters

  • <length>: customized data length. Unit: byte.

Notes

  • The length of customized data cannot exceed 600 bytes.

  • If your ESP chip receives customized data from the phone, the data will be printed in the form of +BLUFIDATA:<len>,<data>.

Example

AT+BLUFISEND=4
// After the symbol ">" shows, input 4 bytes of data, such as "1234". Then the data will be transmitted automatically.

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