Bluetooth LE AT Examples

[中文]

This document provides an introduction and detailed command examples to illustrate how to utilize Bluetooth® Low Energy AT Commands on ESP32-C2.

Introduction

ESP-AT currently only supports Bluetooth LE 4.2 protocol specification, and the description in this document is only for Bluetooth LE 4.2 protocol specification. Please refer to Core Specification 4.2 for more details.

Bluetooth LE protocol architecture

Bluetooth LE protocol stack is divided into several layers from bottom to top: Physical Layer (PHY), Link Layer (LL), Host Controller Interface (HCI), Logical Link Control and Adaptation Protocol Layer (L2CAP), Attribute Protocol (ATT), Security Manager Protocol (SMP), Generic Attribute Profile (GATT), Generic Access Profile (GAP).

• PHY: the PHY layer is responsible for transmitting and receiving packets of information on the physical channel. Bluetooth LE uses 40 RF channels. Frequency Range: 2402 MHz to 2480 MHz.

• LL: the LL layer is responsible for the creation, modification and release of logical links (and, if required, their associated logical transports), as well as the update of parameters related to physical links between devices. It controls the Link Layer state machine in one of the five states of standby, advertising, scanning, initiating and connected.

• HCI: the HCI layer provides a standardized interface to host and controller. This layer can be implemented by software API or controlled by hardware interfaces UART, SPI and USB.

• L2CAP: the L2CAP layer is responsible for protocol multiplexing capability, segmentation, and reassembly operation for data exchanged between the host and the protocol stack.

• ATT: the ATT layer implements the peer-to-peer protocol between an attribute server and an attribute client. The ATT client sends commands, requests, and confirmations to the ATT server. The ATT server sends responses, notifications and indications to the client.

• SMP: the SMP layer is the peer-to-peer protocol used to generate encryption keys and identity keys. The SMP also manages storage of the encryption keys and identity keys and is responsible for generating random addresses and resolving random addresses to known device identities.

• GATT: the GATT layer represents the functionality of the attribute server and, optionally, the attribute client. The profile describes the hierarchy of services, characteristics and attributes used in the attribute server. The layer provides interfaces for discovering, reading, writing and indicating of service characteristics and attributes.

• GAP: the GAP represents the base functionality common to all Bluetooth devices such as modes and access procedures used by the transports, protocols and application profiles. GAP services include device discovery, connection modes, security, authentication, association models and service discovery.

Bluetooth LE role division

There are different roles in different levels of the Bluetooth LE protocol architecture. These divisions are not affected by each other.

• LL: devices can be divided into master and slave, the slave advertises, and the master initiates a connection.

• GAP: GAP defines four specific roles: broadcaster, observer, peripheral, and central.

• GATT: devices can be divided into server and client.

Important

• The Bluetooth LE server and Bluetooth LE client described in this document are both GATT layer roles.

• At present, ESP-AT supports the existence of Bluetooth LE server and Bluetooth LE client at the same time.

• No matter ESP-AT is initialized as Bluetooth LE server or Bluetooth LE client, the maximum number of devices connected at the same time is 3.

GATT is actually an attribute transmission protocol, which can be regarded as an application layer protocol for attribute transmission. The structure of this attribute is very simple. It is composed of services, each service is composed of different numbers of characteristics, and each characteristic is composed of many other elements.

GATT server and GATT client roles exist after the Bluetooth LE connection is established. The GATT server stores the data transported over the Attribute Protocol and accepts Attribute Protocol requests, commands and confirmations from the GATT client. In short, the end that provides data is called GATT server, and the end that accesses data is called GATT client.

Bluetooth LE client reads and write services

Below is an example of using two ESP32-C2 development boards, one as a Bluetooth LE server (only as Bluetooth LE server role), the other one as a Bluetooth LE client (only as Bluetooth LE client role). The example shows how to use Bluetooth LE functions with AT commands.

Important

In the following steps, the operations starting with ESP32-C2 Bluetooth LE server only need to be executed at ESP32-C2 Bluetooth LE server, and the operations starting with ESP32-C2 Bluetooth LE client only need to be executed at ESP32-C2 Bluetooth LE client.

1. Bluetooth LE initialization.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEINIT=2
   

   Response:

   OK
   

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLEINIT=1
   

   Response:

   OK
   

2. ESP32-C2 Bluetooth LE server gets Bluetooth LE address.

   Command:

   AT+BLEADDR?
   

   Response:

   +BLEADDR:"24:0a:c4:d6:e4:46"
   OK
   

   Note:

   • The address you obtain may be different from that in the above response. Keep yours handy as you will need it in one of the following steps.

1. ESP32-C2 Bluetooth LE server discovers characteristics.

   Command:

   AT+BLEGATTSCHAR?
   

   Response:

   +BLEGATTSCHAR:"char",1,1,0xC300
   +BLEGATTSCHAR:"char",1,2,0xC301
   +BLEGATTSCHAR:"char",1,3,0xC302
   +BLEGATTSCHAR:"char",1,4,0xC303
   +BLEGATTSCHAR:"char",1,5,0xC304
   +BLEGATTSCHAR:"char",1,6,0xC305
   +BLEGATTSCHAR:"char",1,7,0xC306
   +BLEGATTSCHAR:"char",1,8,0xC307
   +BLEGATTSCHAR:"char",2,1,0xC400
   +BLEGATTSCHAR:"char",2,2,0xC401
   
   OK
   

2. ESP32-C2 Bluetooth LE server starts advertising, then the ESP32-C2 Bluetooth LE client starts scanning and lasts for 3 s.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEADVSTART
   

   Response:

   OK
   

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLESCAN=1,3
   

   Response:

   OK
   +BLESCAN:"5b:3b:6c:51:90:49",-87,02011a020a0c0aff4c001005071c3024dc,,1
   +BLESCAN:"c4:5b:be:93:ec:66",-84,0201060303111809095647543147572d58020a03,,0
   +BLESCAN:"24:0a:c4:d6:e4:46",-29,,,0
   

   Note:

   • The scan results you obtain may be different from those in the above response.

3. Establish the Bluetooth LE connection.

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLECONN=0,"24:0a:c4:d6:e4:46"
   

   Response:

   +BLECONN:0,"24:0a:c4:d6:e4:46"
   
   OK
   

   Note:

   • When entering the above command, replace the address with your ESP32-C2 Bluetooth LE server address.

   • If the Bluetooth LE connection is established successfully, message +BLECONN:0,"24:0a:c4:d6:e4:46 will be prompted.

   • If the Bluetooth LE connection is broken, message +BLECONN:0,-1 will be prompted.

4. ESP32-C2 Bluetooth LE client discovers services.

   Command:

   AT+BLEGATTCPRIMSRV=0
   

   Response:

   +BLEGATTCPRIMSRV:0,1,0x1800,1
   +BLEGATTCPRIMSRV:0,2,0x1801,1
   +BLEGATTCPRIMSRV:0,3,0xA002,1
   +BLEGATTCPRIMSRV:0,4,0xA003,1
   
   OK
   

   Note:

   • When discovering services, the ESP32-C2 Bluetooth LE client will get two more default services (UUID: 0x1800 and 0x1801) than what the ESP32-C2 Bluetooth LE server will get. So, for the same service, the <srv_index> received by the ESP32-C2 Bluetooth LE client equals the <srv_index> received by the ESP32-C2 Bluetooth LE server + 2. For example, for service 0xA002, the <srv_index> queried on the ESP32-C2 Bluetooth LE client is 3, if the ESP32-C2 Bluetooth LE server is queried through the command AT+BLEGATTSSRV?, then <srv_index> is 1.

5. ESP32-C2 Bluetooth LE client discovers characteristics.

   Command:

   AT+BLEGATTCCHAR=0,3
   

   Response:

   +BLEGATTCCHAR:"char",0,3,1,0xC300,0x02
   +BLEGATTCCHAR:"char",0,3,2,0xC301,0x02
   +BLEGATTCCHAR:"char",0,3,3,0xC302,0x08
   +BLEGATTCCHAR:"char",0,3,4,0xC303,0x04
   +BLEGATTCCHAR:"char",0,3,5,0xC304,0x08
   +BLEGATTCCHAR:"char",0,3,6,0xC305,0x10
   +BLEGATTCCHAR:"desc",0,3,6,1,0x2902
   +BLEGATTCCHAR:"char",0,3,7,0xC306,0x20
   +BLEGATTCCHAR:"desc",0,3,7,1,0x2902
   +BLEGATTCCHAR:"char",0,3,8,0xC307,0x02
   
   OK
   

6. ESP32-C2 Bluetooth LE client reads a characteristic.

   Command:

   AT+BLEGATTCRD=0,3,1
   

   Response:

   +BLEGATTCRD:0,1,0
   
   OK
   

   Note:

   • Please note that the target characteristic’s property has to support the read operation.

   • If the ESP32-C2 Bluetooth LE client reads the characteristic successfully, message +READ:0,"7c:df:a1:b3:8d:de" will be prompted on the ESP32-C2 Bluetooth LE Server side.

7. ESP32-C2 Bluetooth LE client writes a characteristic.

   Command:

   AT+BLEGATTCWR=0,3,3,,2
   

   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.

   OK
   

   Note:

   • If the ESP32-C2 Bluetooth LE client writes the characteristic successfully, message +WRITE:<conn_index>,<srv_index>,<char_index>,[<desc_index>],<len>,<value> will be prompted on the ESP32-C2 Bluetooth LE server side.

8. Indicate a characteristic.

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLEGATTCWR=0,3,7,1,2
   

   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.

   To receive data from ESP32-C2 Bluetooth LE server (through the notify or the indicate method), the ESP32-C2 Bluetooth LE client needs to register with the server in advance. Write the value 0x0001 to use the notify method, and 0x0002 to use the indicate method. This example writes the 0x0002 to use the indicate method.

   OK
   

   Note:

   • If the ESP32-C2 Bluetooth LE client writes the descriptor successfully, message +WRITE:<conn_index>,<srv_index>,<char_index>,<desc_index>,<len>,<value> will be prompted on the ESP32-C2 Bluetooth LE server side.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEGATTSIND=0,1,7,3
   

   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.

   OK
   

   Note:

   • If the ESP32-C2 Bluetooth LE client receives the indication, message +INDICATE:<conn_index>,<srv_index>,<char_index>,<len>,<value> will be prompted.

   • For the same service, the <srv_index> on the ESP32-C2 Bluetooth LE client side equals the <srv_index> on the ESP32-C2 Bluetooth LE server side + 2.

   • For the permissions of the characteristics in the services, please refer to How to Customize Bluetooth® LE Services.

Encrypt Bluetooth LE connection

Below is an example of using two ESP32-C2 development boards, one as a Bluetooth LE server (only as Bluetooth LE server role), the other one as a Bluetooth LE client (only as Bluetooth LE client role). The example shows how to encrypt Bluetooth LE connection.

Important

• In the following steps, the operations starting with ESP32-C2 Bluetooth LE server only need to be executed at ESP32-C2 Bluetooth LE server, and the operations starting with ESP32-C2 Bluetooth LE client only need to be executed at ESP32-C2 Bluetooth LE client.

• Encryption and bonding are two different concepts. bonding is just a long-term key stored locally after successful encryption.

• ESP-AT allows a maximum of 10 devices to be bonded.

1. Bluetooth LE initialization.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEINIT=2
   

   Response:

   OK
   

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLEINIT=1
   

   Response:

   OK
   

2. ESP32-C2 Bluetooth LE server gets Bluetooth LE address.

   Command:

   AT+BLEADDR?
   

   Response:

   +BLEADDR:"24:0a:c4:d6:e4:46"
   OK
   

   Note:

   • The address you obtain may be different from that in the above response. Keep yours handy as you will need it in one of the following steps.

1. ESP32-C2 Bluetooth LE server discovers characteristics.

   Command:

   AT+BLEGATTSCHAR?
   

   Response:

   +BLEGATTSCHAR:"char",1,1,0xC300
   +BLEGATTSCHAR:"char",1,2,0xC301
   +BLEGATTSCHAR:"char",1,3,0xC302
   +BLEGATTSCHAR:"char",1,4,0xC303
   +BLEGATTSCHAR:"char",1,5,0xC304
   +BLEGATTSCHAR:"char",1,6,0xC305
   +BLEGATTSCHAR:"char",1,7,0xC306
   +BLEGATTSCHAR:"char",1,8,0xC307
   +BLEGATTSCHAR:"char",2,1,0xC400
   +BLEGATTSCHAR:"char",2,2,0xC401
   
   OK
   

2. ESP32-C2 Bluetooth LE server starts advertising, then the ESP32-C2 Bluetooth LE client starts scanning and lasts for 3 s.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEADVSTART
   

   Response:

   OK
   

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLESCAN=1,3
   

   Response:

   OK
   +BLESCAN:"5b:3b:6c:51:90:49",-87,02011a020a0c0aff4c001005071c3024dc,,1
   +BLESCAN:"c4:5b:be:93:ec:66",-84,0201060303111809095647543147572d58020a03,,0
   +BLESCAN:"24:0a:c4:d6:e4:46",-29,,,0
   

   Note:

   • The scan results you obtain may be different from those in the above response.

3. Establish the Bluetooth LE connection.

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLECONN=0,"24:0a:c4:d6:e4:46"
   

   Response:

   +BLECONN:0,"24:0a:c4:d6:e4:46"
   
   OK
   

   Note:

   • When entering the above command, replace the address with your ESP32-C2 Bluetooth LE server address.

   • If the Bluetooth LE connection is established successfully, message +BLECONN:0,"24:0a:c4:d6:e4:46 will be prompted.

   • If the Bluetooth LE connection is broken, message +BLECONN:0,-1 will be prompted.

4. ESP32-C2 Bluetooth LE client discovers services.

   Command:

   AT+BLEGATTCPRIMSRV=0
   

   Response:

   +BLEGATTCPRIMSRV:0,1,0x1800,1
   +BLEGATTCPRIMSRV:0,2,0x1801,1
   +BLEGATTCPRIMSRV:0,3,0xA002,1
   +BLEGATTCPRIMSRV:0,4,0xA003,1
   
   OK
   

   Note:

   • When discovering services, the ESP32-C2 Bluetooth LE client will get two more default services (UUID: 0x1800 and 0x1801) than what the ESP32-C2 Bluetooth LE server will get. So, for the same service, the <srv_index> received by the ESP32-C2 Bluetooth LE client equals the <srv_index> received by the ESP32-C2 Bluetooth LE server + 2. For example, for service 0xA002, the <srv_index> queried on the ESP32-C2 Bluetooth LE client is 3, if the ESP32-C2 Bluetooth LE server is queried through the command AT+BLEGATTSSRV?, then <srv_index> is 1.

5. ESP32-C2 Bluetooth LE client discovers characteristics.

   Command:

   AT+BLEGATTCCHAR=0,3
   

   Response:

   +BLEGATTCCHAR:"char",0,3,1,0xC300,0x02
   +BLEGATTCCHAR:"char",0,3,2,0xC301,0x02
   +BLEGATTCCHAR:"char",0,3,3,0xC302,0x08
   +BLEGATTCCHAR:"char",0,3,4,0xC303,0x04
   +BLEGATTCCHAR:"char",0,3,5,0xC304,0x08
   +BLEGATTCCHAR:"char",0,3,6,0xC305,0x10
   +BLEGATTCCHAR:"desc",0,3,6,1,0x2902
   +BLEGATTCCHAR:"char",0,3,7,0xC306,0x20
   +BLEGATTCCHAR:"desc",0,3,7,1,0x2902
   +BLEGATTCCHAR:"char",0,3,8,0xC307,0x02
   
   OK
   

6. Set Bluetooth LE encryption parameters. Set auth_req to SC_MITM_BOND, server’s iocap to KeyboardOnly, client’s iocap to KeyboardDisplay, key_size to 16, init_key to 3, rsp_key to 3.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLESECPARAM=13,2,16,3,3
   

   Response:

   OK
   

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLESECPARAM=13,4,16,3,3
   

   Response:

   OK
   

   Note:

   • In this example, ESP32-C2 Bluetooth LE server enters the pairing code and ESP32-C2 Bluetooth LE client displays the pairing code.

   • ESP-AT supports Legacy Pairing and Secure Connections encryption methods, but the latter has a higher priority. If the peer also supports Secure Connections, then Secure Connections will be used for encryption.

7. ESP32-C2 Bluetooth LE client initiates encryption request.

   Command:

   AT+BLEENC=0,3
   

   Response:

   OK
   

   Note:

   If the ESP32-C2 Bluetooth LE server successfully receives the encryption request, message +BLESECREQ:0 will be prompted on the ESP32-C2 Bluetooth LE server side.

1. ESP32-C2 Bluetooth LE server replies pairing code.

   Command:

   AT+BLEKEYREPLY=0,793718
   

   Response:

   OK
   

   After running this command, there will be corresponding messages prompt on both the ESP32-C2 Bluetooth LE server and the ESP32-C2 Bluetooth LE client.

   ESP32-C2 Bluetooth LE server:

   +BLESECKEYTYPE:0,16
   +BLESECKEYTYPE:0,1
   +BLESECKEYTYPE:0,32
   +BLESECKEYTYPE:0,2
   +BLEAUTHCMPL:0,0
   

   ESP32-C2 Bluetooth LE client:

   +BLESECNTFYKEY:0,793718
   +BLESECKEYTYPE:0,2
   +BLESECKEYTYPE:0,16
   +BLESECKEYTYPE:0,1
   +BLESECKEYTYPE:0,32
   +BLEAUTHCMPL:0,0
   

   You can ignore the message starting with +BLESECKEYTYPE. In terms of the second parameter in the message +BLEAUTHCMPL:0,0, 0 means encryption is successful, and 1 means encryption fails.

Establish SPP connection between two ESP32-C2 development boards and transmit data in UART-Bluetooth LE Passthrough Mode

Below is an example of using two ESP32-C2 development boards, one as a Bluetooth LE server (only as Bluetooth LE server role), the other one as a Bluetooth LE client (only as Bluetooth LE client role). The example shows how to build Bluetooth LE SPP (Serial Port Profile, UART-Bluetooth LE passthrough mode) with AT commands.

Important

In the following steps, the operations starting with ESP32-C2 Bluetooth LE server only need to be executed at ESP32-C2 Bluetooth LE server, and the operations starting with ESP32-C2 Bluetooth LE client only need to be executed at ESP32-C2 Bluetooth LE client.

1. Bluetooth LE initialization.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEINIT=2
   

   Response:

   OK
   

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLEINIT=1
   

   Response:

   OK
   

1. ESP32-C2 Bluetooth LE server gets Bluetooth LE address.

   Command:

   AT+BLEADDR?
   

   Response:

   +BLEADDR:"24:0a:c4:d6:e4:46"
   OK
   

   Note:

   • The address you obtain may be different from that in the above response. Keep yours handy as you will need it in one of the following steps.

2. ESP32-C2 Bluetooth LE server sets advertising parameters.

   Command:

   AT+BLEADVPARAM=50,50,0,0,7,0,,
   

   Response:

   OK
   

3. ESP32-C2 Bluetooth LE server sets advertising data.

   Command:

   AT+BLEADVDATA="0201060A09457370726573736966030302A0"
   

   Response:

   OK
   

4. ESP32-C2 Bluetooth LE server starts advertising.

   Command:

   AT+BLEADVSTART
   

   Response:

   OK
   

5. ESP32-C2 Bluetooth LE client enables a scanning for three seconds.

   Command:

   AT+BLESCAN=1,3
   

   Response:

   OK
   +BLESCAN:"24:0a:c4:d6:e4:46",-78,0201060a09457370726573736966030302a0,,0
   +BLESCAN:"45:03:cb:ac:aa:a0",-62,0201060aff4c001005441c61df7d,,1
   +BLESCAN:"24:0a:c4:d6:e4:46",-26,0201060a09457370726573736966030302a0,,0
   

   Note:

   • The scan results you obtain may be different from those in the above response.

6. Establish the Bluetooth LE connection.

   ESP32-C2 Bluetooth LE client:

   Command:

   AT+BLECONN=0,"24:0a:c4:d6:e4:46"
   

   Response:

   +BLECONN:0,"24:0a:c4:d6:e4:46"
   
   OK
   

   Note:

   • When entering the above command, replace the address your ESP32-C2 Bluetooth LE server address.

   • If the Bluetooth LE connection is established successfully, message +BLECONN:0,"24:0a:c4:d6:e4:46 will be prompted.

   • If the Bluetooth LE connection is broken, message +BLECONN:0,-1 will be prompted.

7. ESP32-C2 Bluetooth LE server discovers local services.

   Command:

   AT+BLEGATTSSRV?
   

   Response:

   +BLEGATTSSRV:1,1,0xA002,1
   +BLEGATTSSRV:2,1,0xA003,1
   
   OK
   

8. ESP32-C2 Bluetooth LE server discovers local characteristics.

   Command:

   AT+BLEGATTSCHAR?
   

   Response:

   +BLEGATTSCHAR:"char",1,1,0xC300
   +BLEGATTSCHAR:"char",1,2,0xC301
   +BLEGATTSCHAR:"char",1,3,0xC302
   +BLEGATTSCHAR:"char",1,4,0xC303
   +BLEGATTSCHAR:"char",1,5,0xC304
   +BLEGATTSCHAR:"char",1,6,0xC305
   +BLEGATTSCHAR:"char",1,7,0xC306
   +BLEGATTSCHAR:"char",1,8,0xC307
   +BLEGATTSCHAR:"char",2,1,0xC400
   +BLEGATTSCHAR:"char",2,2,0xC401
   
   OK
   

9. ESP32-C2 Bluetooth LE client discovers services.

   Command:

   AT+BLEGATTCPRIMSRV=0
   

   Response:

   +BLEGATTCPRIMSRV:0,1,0x1800,1
   +BLEGATTCPRIMSRV:0,2,0x1801,1
   +BLEGATTCPRIMSRV:0,3,0xA002,1
   +BLEGATTCPRIMSRV:0,4,0xA003,1
   
   OK
   

   Note:

   • When discovering services, the ESP32-C2 Bluetooth LE client will get two more default services (UUID: 0x1800 and 0x1801) than what the ESP32-C2 Bluetooth LE server will get. So, for the same service, the <srv_index> received by the ESP32-C2 Bluetooth LE client equals the <srv_index> received by the ESP32-C2 Bluetooth LE server + 2. For example, for service 0xA002, the <srv_index> queried on the ESP32-C2 Bluetooth LE client is 3, if the ESP32-C2 Bluetooth LE server is queried through the command AT+BLEGATTSSRV?, then <srv_index> is 1.

10. ESP32-C2 Bluetooth LE client discovers characteristics.

    Command:

    AT+BLEGATTCCHAR=0,3
    

    Response:

    +BLEGATTCCHAR:"char",0,3,1,0xC300,0x02
    +BLEGATTCCHAR:"char",0,3,2,0xC301,0x02
    +BLEGATTCCHAR:"char",0,3,3,0xC302,0x08
    +BLEGATTCCHAR:"char",0,3,4,0xC303,0x04
    +BLEGATTCCHAR:"char",0,3,5,0xC304,0x08
    +BLEGATTCCHAR:"char",0,3,6,0xC305,0x10
    +BLEGATTCCHAR:"desc",0,3,6,1,0x2902
    +BLEGATTCCHAR:"char",0,3,7,0xC306,0x20
    +BLEGATTCCHAR:"desc",0,3,7,1,0x2902
    +BLEGATTCCHAR:"char",0,3,8,0xC307,0x02
    
    OK
    

11. ESP32-C2 Bluetooth LE client Configures Bluetooth LE SPP.

    Set a characteristic that enables writing permission to TX channel for sending data. Set another characteristic that supports notification or indication to RX channel for receiving data.

    Command:

    AT+BLESPPCFG=1,3,5,3,7
    

    Response:

    OK
    

12. ESP32-C2 Bluetooth LE client enables Bluetooth LE SPP.

    Command:

    AT+BLESPP
    

    Response:

    OK
    
    >
    

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

    Note:

    • After the ESP32-C2 Bluetooth LE client enables Bluetooth LE SPP, data received from serial port will be transmitted to the Bluetooth LE server directly.

13. ESP32-C2 Bluetooth LE server Configures Bluetooth LE SPP.

    Set a characteristic that supports notification or indication to TX channel for sending data. Set another characteristic that enables writing permission to RX channel for receiving data.

    Command:

    AT+BLESPPCFG=1,1,7,1,5
    

    Response:

    OK
    

14. ESP32-C2 Bluetooth LE server enables Bluetooth LE SPP.

    Command:

    AT+BLESPP
    

    Response:

    OK
    
    >
    

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

    Note:

    • After the ESP32-C2 Bluetooth LE server enables Bluetooth LE SPP, the data received from serial port will be transmitted to the Bluetooth LE client directly.

    • If the ESP32-C2 Bluetooth LE client does not enable Bluetooth LE SPP first, or uses other device as Bluetooth LE client, then the Bluetooth LE client needs to listen to the notification or indication first. For example, if the ESP32-C2 Bluetooth LE client does not enable Bluetooth LE SPP first, then it should use command AT+BLEGATTCWR=0,3,7,1,1 to enable listening function first, so that the ESP32-C2 Bluetooth LE server can transmit successfully.

    • For the same service, the <srv_index> on the ESP32-C2 Bluetooth LE client side equals the <srv_index> on the ESP32-C2 Bluetooth LE server side + 2.

Establish SPP connection between ESP32-C2 and mobile phone and transmit data in UART-Bluetooth LE passthrough mode

The example shows how to establish SPP connection between an ESP32-C2 development board (only serving as the Bluetooth LE server role) and a mobile phone (only serve as the Bluetooth LE client role) and how to transmit data between them in UART-Bluetooth LE passthrough mode.

Important

In the following steps, the operations starting with ESP32-C2 Bluetooth LE server only need to be executed at ESP32-C2 Bluetooth LE server, and those starting with ESP32-C2 Bluetooth LE client only need to be executed on the Bluetooth debugging assistant of the mobile phone.

1. First, you need to download the Bluetooth LE debugging assistant on the mobile phone, such as LightBlue.

2. Bluetooth LE initialization.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEINIT=2
   

   Response:

   OK
   

1. ESP32-C2 Bluetooth LE server gets its MAC address.

   Command:

   AT+BLEADDR?
   

   Response:

   +BLEADDR:"24:0a:c4:d6:e4:46"
   OK
   

   Note:

   • The address you obtain may be different from that in the above response. Keep yours handy as you will need it in one of the following steps.

2. ESP32-C2 Bluetooth LE server sets advertising parameters.

   Command:

   AT+BLEADVPARAM=50,50,0,0,7,0,,
   

   Response:

   OK
   

3. ESP32-C2 Bluetooth LE server sets advertising data.

   Command:

   AT+BLEADVDATA="0201060A09457370726573736966030302A0"
   

   Response:

   OK
   

4. ESP32-C2 Bluetooth LE server starts advertising.

   Command:

   AT+BLEADVSTART
   

   Response:

   OK
   

5. Establish the Bluetooth LE connection.

   Open the LightBlue application on your mobile phone, and click SCAN to start scanning. When you find the MAC address of the ESP32-C2 Bluetooth LE server, click CONNECT. Then, ESP32-C2 should print the log similar to +BLECONN:0,"60:51:42:fe:98:aa", which indicates that Bluetooth LE connection has been established.

6. ESP32-C2 Bluetooth LE server discovers local services.

   Command:

   AT+BLEGATTSSRV?
   

   Response:

   +BLEGATTSSRV:1,1,0xA002,1
   +BLEGATTSSRV:2,1,0xA003,1
   
   OK
   

7. ESP32-C2 Bluetooth LE server discovers local characteristics.

   Command:

   AT+BLEGATTSCHAR?
   

   Response:

   +BLEGATTSCHAR:"char",1,1,0xC300
   +BLEGATTSCHAR:"char",1,2,0xC301
   +BLEGATTSCHAR:"char",1,3,0xC302
   +BLEGATTSCHAR:"char",1,4,0xC303
   +BLEGATTSCHAR:"char",1,5,0xC304
   +BLEGATTSCHAR:"char",1,6,0xC305
   +BLEGATTSCHAR:"char",1,7,0xC306
   +BLEGATTSCHAR:"char",1,8,0xC307
   +BLEGATTSCHAR:"char",2,1,0xC400
   +BLEGATTSCHAR:"char",2,2,0xC401
   
   OK
   

8. ESP32-C2 Bluetooth LE client discovers characteristics.

   Click the button of the service feature whose Properties is NOTIFY or INDICATE in the mobile phone LightBlue client (here ESP-AT default Properties The service characteristics of NOTIFY or INDICATE are 0xC305 and 0xC306) and start to listen for the service characteristics of NOTIFY or INDICATE.

9. ESP32-C2 Bluetooth LE server configures Bluetooth LE SPP.

   Set a characteristic that supports notification or indication to TX channel for sending data. Set another characteristic that enables writing permission to RX channel for receiving data.

   Command:

   AT+BLESPPCFG=1,1,7,1,5
   

   Response:

   OK
   

10. ESP32-C2 Bluetooth LE server enables Bluetooth LE SPP.

    Command:

    AT+BLESPP
    

    Response:

    OK
    
    >
    

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

11. Bluetooth LE client sends data.

    In the LightBlue client, select the 0xC304 service characteristic value and send the data test to the ESP32-C2 Bluetooth LE server. Then, the ESP32-C2 Bluetooth LE server can receive the test.

12. ESP32-C2 Bluetooth LE server sends data.

    The ESP32-C2 Bluetooth LE server sends test, and then the LightBlue client can receive test.

Establish Bluetooth LE connection and pairing between ESP32-C2 and mobile phone

This example shows how to establish a Bluetooth LE connection between the ESP32-C2 development board (only as a Bluetooth LE server role) and a mobile phone (only as a Bluetooth LE client role) and enter the passkey to complete the pairing.

Important

In the following steps, the operations starting with ESP32-C2 Bluetooth LE server only need to be executed at ESP32-C2 Bluetooth LE server, and those starting with ESP32-C2 Bluetooth LE client only need to be executed on the Bluetooth debugging assistant of the mobile phone.

1. First, you need to download the Bluetooth LE debugging assistant on the mobile phone, such as LightBlue.

2. Bluetooth LE initialization.

   ESP32-C2 Bluetooth LE server:

   Command:

   AT+BLEINIT=2
   

   Response:

   OK
   

1. ESP32-C2 Bluetooth LE server gets its MAC address.

   Command:

   AT+BLEADDR?
   

   Response:

   +BLEADDR:"24:0a:c4:d6:e4:46"
   OK
   

   Note:

   • The address you obtain may be different from that in the above response. Keep yours handy as you will need it in one of the following steps.

2. ESP32-C2 Bluetooth LE server sets advertising parameters.

   Command:

   AT+BLEADVPARAM=50,50,0,0,7,0,,
   

   Response:

   OK
   

3. ESP32-C2 Bluetooth LE server sets advertising data.

   Command:

   AT+BLEADVDATA="0201060A09457370726573736966030302A0"
   

   Response:

   OK
   

4. ESP32-C2 Bluetooth LE server sets encryption parameters.

   Command:

   AT+BLESECPARAM=13,2,16,3,3
   

   Response:

   OK
   

5. ESP32-C2 Bluetooth LE server starts advertising.

   Command:

   AT+BLEADVSTART
   

   Response:

   OK
   

6. Establish the Bluetooth LE connection.

   Open the LightBlue application on your mobile phone, and click SCAN to start scanning. When you find the MAC address of the ESP32-C2 Bluetooth LE server, click CONNECT. Then, ESP32-C2 should print the log similar to +BLECONN:0,"60:51:42:fe:98:aa", which indicates that Bluetooth LE connection has been established.

7. ESP32-C2 Bluetooth LE server initiates encryption request.

   Command:

   AT+BLEENC=0,3
   

   Response:

   OK
   

8. Bluetooth LE client accepts pairing.

   The pairing information (including the pairing key, for example: 231518) will pop up on the Bluetooth LE connection page that has just been successfully created on the LightBlue, and then click “Pairing”. At this time, the ESP32-C2 Bluetooth LE server should print a log similar to +BLESECKEYREQ:0, indicating that the phone has responded to pairing, and the ESP32-C2 Bluetooth LE server can enter the key.

9. ESP32-C2 Bluetooth LE server replies with the pairing key.

   At this time, the key that the Bluetooth LE server should reply with is the key (231518) contained in the pairing information that popped up on LightBlue in the previous step.

   Command:

   AT+BLEKEYREPLY=0,231518
   

   Response:

   OK
   

   At this time, the ESP32-C2 Bluetooth LE server will print a log similar to the following, which means that the ESP32-C2 Bluetooth LE server has successfully paired with the phone Bluetooth LE client.

   +BLESECKEYTYPE:0,16
   +BLESECKEYTYPE:0,1
   +BLESECKEYTYPE:0,32
   +BLESECKEYTYPE:0,2
   +BLEAUTHCMPL:0,0
   

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