STM32WB0 Bluetooth® LE – Peer 2 Peer Applications

1. Peer to Peer Profile

The Peer to Peer Profile is a Generic Attribute Profile (GATT) based low-energy profile defined by STMicroelectronics with proprietary UUIDs(128 bits).
The Peer to Peer Profile, widely used for direct connection, defines the communication between a GATT-server of a Peer to Peer Server device, and a GATT-client Collector device, such as a smartphone, STM32WB0 Peer to Peer Client or Peer to Peer Router devices.

The Peer to Peer Server

• Contains the P2P Service, which exposes two characteristics (Notification and Write) in order to create a bi-directional data communication.
• Is the GATT server

The Collector

• Accesses the information exposed by Peer to Peer Server, controls it with the Write characteristics, receives Notification from it.
• Is the GATT client

This wiki page is the description of the Peer to Peer Server and Peer to Peer Client projects provided within the STM32CubeWB0 MCU Package

Refer to the following page for the Peer to Peer Router project explanation.

Bluetooth® LE Peer to Peer Profile & STM32WB0

1.1. STM32WB0 Peer to Peer Server application

The table below describes the structure of Peer to Peer service:

Bluetooth® LE Peer to Peer Service specification
Service Characteristic Mode UUID size P2P Service 0000FE40-cc7a-482a-984a-7f2ed5b3e58f LED Write without Response/Read 0000FE41-8e22-4541-9d4c-21edae82ed19 2 SWITCH Notify 0000FE42-8e22-4541-9d4c-21edae82ed19 2

Peer To Peer Server is exported as a Service

• LED characteristics:
  • Used to control LED1 (Blue) on STM32WB0 platform by remote device .

Peer to Peer Service - LED Characteristic
Byte Index 0 1 Name LED Selection LED Level Value 0x01: Blue LED 0x00: LED off 0x01: LED on

• SWITCH Characteristic:
  • Used to switch LED or Lamp on Collector device.

Peer to Peer Service - SWITCH Characteristic
Byte Index 0 1 Name Button Selection Status Value 0x01: button 1 0x00 or 0x01

Example of flow diagram between STM32WB0 & ST BLE Toolbox

1.2. Advertising data

At startup, Peer To Peer Server application starts Advertising.
Data advertised are composed as follows:

P2P Server Advertising packet
Description Length AD Type Value Device Name 8 0x09 p2pS_XX (XX: last byte of BD address) Manufacturer Data 15 0xFF See table below Flags 2 0x01 0x06 (GeneralDiscoverable, BrEdrNotSupported)

The manufacturer data are encoded following the STMicroelectronics BlueST SDK v2 as described below:

STMicroelectronics Manufacturer Advertising data
Byte Index 0 1 2-3 4 5 6 7 8 9 10-15 Function Length Manufacturer ID Company BlueST SDK Version Device ID Firmware ID Option 1 Option 2 Option 3 Device Address Value 0x0F 0xFF 0x0030 STMicro 0x02 0x8D Nucleo-WB0 0x83 - P2P Server 0x00 0x00 0x00 0x08E12Axxxx

Information

Advertising is stopped after 30s. You can press B1 to restart it.

1.3. STM32WB0 Peer to Peer Client application

It acts as a Central device with the support of GATT Client Layer.
At startup, by pressing B1 button, Peer To Peer Client application:

• Starts scanning to detect Peer To Peer Server application by filtering the Firmware ID of the STMicroelectronics Manufacturer advertising data
• Stops Scanning once P2P server detected
• Connects to the P2P Server to establish the connection.
• Discovers GATT Service & Characteristics of the P2P server
• Enable all GATT server notification characteristics

Once connected, the Peer To Peer Client application:

• By pressing B1 button, write a message to toggle the Blue LED of the P2P Server
• Receive notification to toggle the on board Blue LED from remote P2P Server Application.

Example of flow diagram between STM32WB0 P2P Server & P2P Client

1.4. On board buttons configuration

Buttons configuration for Bluetooth® Low Energy P2P Application on STM32WB0 Serie Nucleo boards
Application Condition B1 Click B1 Long Press B2 Click B2 Long Press B3 Click B3 Long Press P2P Server Idle Connected Adv start Notification / Clear Sec db Adv start (Multi conn) / - L2CAP CONN REQ / P2P Client Idle Connected Start Scan Write Char / Clear Sec db - / - Change Conn Int /

2. Requirements

2.1. Software and Hardware requirements

For software and hardware requirements, refer to the STM32WB0 Build BLE Project wiki page.

2.2. Collector applications compatible

The STM32CubeWB0 Peer To Peer Server project is compatible with the following collector:

• ST BLE Sensor
• ST BLE ToolBox

3. STM32WB0 P2P Server & P2P Client examples description

3.1. Project directory

The "BLE_p2pServer" & "BLE_p2pClient"applications are available by downloading STM32CubeWB0 MCU Package.

Refer to How to Build a Bluetooth^® LE project wiki page for project directory information.

3.2. Project description

3.2.1. Structure

Software project structure with the most important parts:

P2P Server / Client project structure
Main applicative part files Services management Bluetooth® Low Energy libraries Bluetooth® Low Energy stack modular configuration options and event dispatcher files WARNING: Do not modify the files in Middlewares folder

3.2.2. Application initialization

The different steps of the application initialization are described below:

P2P Server project initialization
Initialize the system (HAL, clocks, peripherals). HAL_Init(); SystemClock_Config(); PeriphCommonClock_Config(); MX_GPIO_Init(); MX_RADIO_Init(); MX_RADIO_TIMER_Init(); MX_PKA_Init(); MX_APPE_Init(); Initialize the RNG, AES block, PKA: HW_RNG_Init(); HW_AES_Init(); HW_PKA_Init(); APP_BLE_Init(); Initialize the Bluetooth® LE Host Stack BLE_Init(); Initialize the Bluetooth® LE GATT level Initialize the Bluetooth® LE GAP level P2P_SERVER_APP_Init(); Initialize the Application/Profile context (Services, Characteristics) Manage the Peer 2 Peer Service notification P2P_SERVER_Init(); /* p2p_server.c */ Register Service Handler Update services and characteristics
P2P Client project initialization
Initialize the system (HAL, clocks, peripherals). HAL_Init(); SystemClock_Config(); PeriphCommonClock_Config(); MX_GPIO_Init(); MX_RADIO_Init(); MX_RADIO_TIMER_Init(); MX_PKA_Init(); MX_APPE_Init(); Initialize the RNG, AES block, PKA: HW_RNG_Init(); HW_AES_Init(); HW_PKA_Init(); APP_BLE_Init(); Initialize the Bluetooth® LE Host Stack BLE_Init(); Initialize the Bluetooth® LE GATT level Initialize the Bluetooth® LE GAP level GATT_CLIENT_APP_Init(); Initialize the Application/Profile context (Services, Characteristics) Register Service Handler

3.2.3. GAP and GATT initialization and interaction

P2P Server:

P2P Server software module interaction

and The Bluetooth® LE P2P Server application initialization is done within app_ble.c

• Initialize the Bluetooth^® Low Energy stack - initialize the device as peripheral - configure and start advertising: ADV parameters, local name, UUID - APP_BLE_init()
• Call the services controller initialization BLEEVT_Init() - ble_evt.c.
• Manage the GAP event - BLEEVT_App_Notification() - ble_evt.c
  • HCI_LE_CONNECTION_COMPLETE_SUBEVT_CODE- provides information of the connection interval, slave latency, supervision timeout
  • HCI_LE_CONNECTION_UPDATE_COMPLETE_SUBEVT_CODE- provides the new information of the connection
  • HCI_DISCONNECTION_COMPLETE_EVT_CODE- informs the application about the link disconnection and the reason

Event management is done by the Bluetoooth® Low Energy Event Dispatcher, ble_evt.c

• Initialize the number of registered handler - BLEEVT_Init()
• Manage events - BLE_STACK_Event()- from the Bluetooth^® Low Energy Host Stack and redirect them to the gap event handler - BLEEVT_App_Notification()

The application level of the P2P Server is done with p2p_server_app.c:

• Initialization of the services:
  • P2P Server Service - P2P_SERVER_Init() - p2p_server.c
• Initialization of the context of the application
• Receive notification from the P2P Server Service - P2P_SERVER_Notification()
• When P2P_SERVER_LED_C_WRITE_NO_RESP_EVT event is received from the P2P Client, the blue LED is toggled.
• P2P_SERVER_Switch_c_SendNotification() function is called on Button B1 press, to notify the P2P Client:
  • P2P_SERVER_UpdateValue() is called with the notification data - p2p_server.c

The Custom P2P Server Service p2p_server.c manages the specification of the service:

• Service Init - P2P_SERVER_Init()
  • Register P2P Server Event Handle to Service Controller - BLEEVT_RegisterGattEvtHandler();
  • Initialize Service UUID – add P2P Server service as Primary services
    • Initialize LED_C characteristic
    • Initialize SWITCH_C characteristic
• Manage the GATT event from Bluetooth^® Low Energy Stack - P2P_SERVER_EventHandler()
  • ACI_GATT_SRV_ATTRIBUTE_MODIFIED_VSEVT_CODE
    • Reception of an attribute modification - LED C Value : ON or OFF Indication
      • Notify application of the Measurement Notification - P2P_SERVER_Notification(P2P_SERVER_LED_C_WRITE_NO_RESP_EVT)
        

        notification.EvtOpcode = P2P_SERVER_LED_C_WRITE_NO_RESP_EVT;         
        P2P_SERVER_Notification(&notification);
        

P2P Client:

P2P Client software module interaction

and The Bluetooth LE P2P Client application initialization is done within app_ble.c

• Initialize the Bluetooth^® Low Energy stack - initialize the device as peripheral - configure and start advertising: ADV parameters, local name, UUID - APP_BLE_init()
• Call the services controller initialization BLEEVT_Init() - ble_evt.c.
• Manage the GAP event - BLEEVT_App_Notification().
  • HCI_LE_CONNECTION_COMPLETE_SUBEVT_CODE- provides information of the connection interval, slave latency, supervision timeout
  • HCI_LE_CONNECTION_UPDATE_COMPLETE_SUBEVT_CODE- provides the new information of the connection
  • HCI_DISCONNECTION_COMPLETE_EVT_CODE- informs the application about the link disconnection and the reason

Event management is done by the Bluetoooth® Low Energy Event Dispatcher, ble_evt.c

• Initialize the number of registered handler - BLEEVT_Init()
• Manage events - BLE_STACK_Event()- from the Bluetooth^® Low Energy Host Stack and redirect them to the gap event handler - BLEEVT_App_Notification()

The application level of the P2P Client is done with gatt_client_app.c:

• Initialization of the application context
  • Register Event Handler to Bluetooth^® Low Energy Controller - P2P_CLIENT_EventHandler();
  • Initialize LED data level and selection
• Manage the GATT event from Bluetooth^® Low Energy Stack - gatt_parse_notification()
  • ACI_GATT_CLT_NOTIFICATION_VSEVT_CODE
    • When the notification event is received from the P2P Server, the blue LED is toggled - gatt_Notification()
• Write characteristic to P2P Server (LED toggling) - P2Pclient_write_char() - by pressing Button B1 while connected.

3.3. How to use the Bluetooth^® Low Energy P2P Server and P2P Client applications

P2P Server VS Smartphone
Once the BLE P2P Server application is installed on the STM32WB0 platform, launch ST BLE ToolBox smartphone application.

Then, scan and connect the device called p2pS_XX (where XX is replaced by the last byte of the BD address) to the application.
Once the Bluetooth^® LE connection is established and the notification enabled by the smartphone (by clicking on P2P Server icon):

• LED_C value can be modified by clicking on the LED button on smartphone interface, the blue LED of the Nucleo board is switched On/Off accordingly.
• Pressing Button B1 on the board while connected sends a SWITCH_C notification to the smartphone and the switch level is updated on the smartphone interface.

P2P Server VS P2P Client
At least two Nucleo platforms are required, one flashed with the BLE P2P Server application and one with the BLE P2P Client application.

• On P2P Client side:
  • Pressing Button B1 on the P2P Client platform while not connected, starts a scan procedure, and a connection is done if a P2P Server platform is found.
  • Pressing Button B1 on the P2P Client platform while connected, sends a GATT event to the P2P Server platform in order to switch On/Off the server blue LED.

• On P2P Server side:
  • Pressing Button B1 on the P2P Server side while connected sends a SWITCH_C notification to the P2P Client platform and toggles the blue LED on client side.
  • Pressing Button B2 on the P2P Server side while connected, starts a new advertising in order to illustrate multi link feature.
  • Pressing Button B2 on the P2P Server side while not connected, clears the security DataBase of the platform.

3.4. UART debug trace

Thanks to the debug log via UART interface, it is possible to trace the application project.

To enable the traces within the project, enable them within app_conf.h as described below:

/**
 * Enable or Disable traces in application
 */
#define CFG_DEBUG_APP_TRACE         (1)

P2P Server - Initialization phase	P2P Server - Connected Phase and LED On notification
==>> Start BLE_Init function Success: aci_hal_set_tx_power_level command Success: aci_gatt_srv_profile_init command Success: aci_gap_init command Static Random Bluetooth Address: fa:97:57:3a:5b:50 Success: Gap_profile_set_dev_name - Device Name Success: Gap_profile_set_appearance - Appearance Success: hci_le_set_default_phy command Success: aci_gap_set_io_capability command Success: aci_gap_set_security_requirements command Success: aci_gap_configure_filter_accept_and_resolving_list command ==>> End BLE_Init function Services and Characteristics creation Success: aci_gatt_srv_add_service command: p2p_Server End of Services and Characteristics creation Success: aci_hal_set_radio_activity_mask command ==>> Success: aci_gap_set_advertising_configuration ==>> Success: aci_gap_set_advertising_data ==>> Success: aci_gap_set_advertising_enable ==>> Success: Start Advertising	>>== hci_le_connection_complete_event - Connection handle: 0x0801 - Connection established with @:61:7b:8d:4f:4a:29 - Connection Interval: 45.00 ms - Connection latency: 0 - Supervision Timeout: 5000 ms Success: aci_gatt_confirm_indication command HCI_VENDOR_EVT: 0x0C0E HCI_VENDOR_EVT: 0x0C17 >>== HCI_LE_CONNECTION_UPDATE_COMPLETE_SUBEVT_CODE - Connection Interval: 7.50 ms - Connection latency: 0 - Supervision Timeout: 5000 ms >>== HCI_LE_CONNECTION_UPDATE_COMPLETE_SUBEVT_CODE - Connection Interval: 45.00 ms - Connection latency: 0 - Supervision Timeout: 5000 ms HCI_VENDOR_EVT: 0x0C01 HCI_VENDOR_EVT: 0x0C03 -- P2P APPLICATION SERVER : NOTIFICATION ENABLED
P2P Client - Initialization phase	P2P Client - Connected Phase and LED On notification
==>> Start BLE_Init function Success: aci_hal_set_tx_power_level command Success: aci_gatt_srv_profile_init command Success: aci_gap_init command Static Random Bluetooth Address: c0:d5:34:ed:fe:95 Success: Gap_profile_set_dev_name - Device Name Success: Gap_profile_set_appearance - Appearance Success: aci_gap_set_io_capability command Success: aci_gap_set_security_requirements command Success: aci_gap_configure_filter_accept_and_resolving_list command ==>> End BLE_Init function	==>> aci_gap_set_scan_configuration - Success ==>> aci_gap_start_procedure - Success P2P server, db addr 0xDE:84:76:49:53:4B ==>> aci_gap_terminate_gap_proc - Success >>== ACI_GAP_PROC_COMPLETE_VSEVT_CODE -- GAP_GENERAL_DISCOVERY_PROC completed Create connection to P2Pserver ==>> aci_gap_set_connection_configuration Success , result: 0x00 wait for event HCI_LE_CONNECTION_COMPLETE_SUBEVT_CODE HCI_LE_META_EVT: 0x14 >>== hci_le_connection_complete_event - Connection handle: 0x0801 - Connection established with @:de:84:76:49:53:4b - Connection Interval: 50.00 ms - Connection latency: 0 - Supervision Timeout: 5000 ms >>== ACI_GAP_PROC_COMPLETE_VSEVT_CODE GATT services discovery ACI_ATT_READ_BY_GROUP_TYPE_RESP_VSEVT_CODE - ConnHdl=0x0801 1/2 short UUID=0x1801, handle [0x0001 - 0x000A], GENERIC_ATTRIBUTE_SERVICE_UUID found 2/2 short UUID=0x1800, handle [0x000B - 0x000F], GAP_SERVICE_UUID found HCI_VENDOR_EVT: 0x0C0A ACI_ATT_READ_BY_GROUP_TYPE_RESP_VSEVT_CODE - ConnHdl=0x0801 1/1 short UUID=0xFE40, handle [0x0010 - 0x0015], P2P_SERVICE_UUID found HCI_VENDOR_EVT: 0x0C0A HCI_VENDOR_EVT: 0x0C11 HCI_VENDOR_EVT: 0x0C10 PROC_GATT_CTL_DISC_ALL_PRIMARY_SERVICES services discovered Successfully DISCOVER_ALL_CHARS ConnHdl=0x0801 ALLServiceHandle[0x0001 - 0x0015] ACI_ATT_READ_BY_TYPE_RESP_VSEVT_CODE - ConnHdl=0x0801 ConnHdl=0x0801, number of value pair = 3 1/3 short UUID=0x2A05, Properties=0x0020, CharHandle [0x0002 - 0x0003], GATT SERVICE_CHANGED_CHARACTERISTIC_UUID charac found 2/3 short UUID=0x2B29, Properties=0x000A, CharHandle [0x0005 - 0x0006] 3/3 short UUID=0x2B2A, Properties=0x0002, CharHandle [0x0007 - 0x0008] HCI_VENDOR_EVT: 0x0C06 ACI_ATT_READ_BY_TYPE_RESP_VSEVT_CODE - ConnHdl=0x0801 ConnHdl=0x0801, number of value pair = 3 1/3 short UUID=0x2B3A, Properties=0x0002, CharHandle [0x0009 - 0x000A] 2/3 short UUID=0x2A00, Properties=0x0002, CharHandle [0x000C - 0x000D], GAP DEVICE_NAME charac found 3/3 short UUID=0x2A01, Properties=0x0002, CharHandle [0x000E - 0x000F], GAP APPEARANCE charac found HCI_VENDOR_EVT: 0x0C06 ACI_ATT_READ_BY_TYPE_RESP_VSEVT_CODE - ConnHdl=0x0801 ConnHdl=0x0801, number of value pair = 1 1/1 short UUID=0xFE41, Properties=0x0006, CharHandle [0x0011 - 0x0012], ST_P2P_WRITE_CHAR_UUID charac found HCI_VENDOR_EVT: 0x0C06 ACI_ATT_READ_BY_TYPE_RESP_VSEVT_CODE - ConnHdl=0x0801 ConnHdl=0x0801, number of value pair = 1 1/1 short UUID=0xFE42, Properties=0x0010, CharHandle [0x0013 - 0x0014], ST_P2P_NOTIFY_CHAR_UUID charac found HCI_VENDOR_EVT: 0x0C06 HCI_VENDOR_EVT: 0x0C11 HCI_VENDOR_EVT: 0x0C10 All characteristics discovered Successfully DISCOVER_ALL_CHAR_DESCS [0x0001 - 0x0015] ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x0002 UUID=0x2A05, handle=0x0003, found GATT SERVICE_CHANGED_CHARACTERISTIC_UUID Descriptor UUID=0x2902, handle=0x0002-0x0003-0x0004, Service Changed found reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x0005 UUID=0x2B29, handle=0x0006 HCI_VENDOR_EVT: 0x0C04 ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x0007 UUID=0x2B2A, handle=0x0008 reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x0009 UUID=0x2B3A, handle=0x000A PRIMARY_SERVICE_UUID=0x2800 handle=0x000B HCI_VENDOR_EVT: 0x0C04 ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x000C UUID=0x2A00, handle=0x000D, found GAP DEVICE_NAME_UUID reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x000E UUID=0x2A01, handle=0x000F, found GAP APPEARANCE_UUID PRIMARY_SERVICE_UUID=0x2800 handle=0x0010 HCI_VENDOR_EVT: 0x0C04 ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x0011 HCI_VENDOR_EVT: 0x0C04 ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 UUID=0xFE41, handle=0x0012, found ST_P2P_WRITE_CHAR_UUID HCI_VENDOR_EVT: 0x0C04 ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 reset - UUID & handle - CHARACTERISTIC_UUID=0x2803 CharStartHandle=0x0013 HCI_VENDOR_EVT: 0x0C04 ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 UUID=0xFE42, handle=0x0014, found ST_P2P_NOTIFY_CHAR_UUID HCI_VENDOR_EVT: 0x0C04 ACI_ATT_FIND_INFO_RESP_VSEVT_CODE - ConnHdl=0x0801 Descriptor UUID=0x2902, handle=0x0013-0x0014-0x0015P2PNotification found : Desc UUID=0x2902 handle=0x0013-0x0014-0x0015 HCI_VENDOR_EVT: 0x0C04 HCI_VENDOR_EVT: 0x0C10 All characteristic descriptors discovered Successfully HCI_VENDOR_EVT: 0x0C11 HCI_VENDOR_EVT: 0x0C10 ServiceChangedCharDescHdl =0x0004 HCI_VENDOR_EVT: 0x0C10 P2PNotificationDescHdl =0x0015 All notifications enabled Successfully ACI_GATT_NOTIFICATION_VSEVT_CODE - ConnHdl=0x0801, Attribute_Handle=0x0014 Incoming Nofification received P2P Server information P2P APPLICATION CLIENT : NOTIFICATION RECEIVED - LED ON HCI_VENDOR_EVT: 0x0C0F

4. P2P Client - smartphone application

4.1. ST BLE ToolBox application

Once the BLE P2P Server application is installed on the STM32WB0 platform, launch the ST BLE ToolBox smartphone application. The application starts scanning and allows to see advertisement data or to connect to the device. Once the device is connected an interface allows to switch On/Off the blue LED of the platform, and a notification reflect the Switch_C characteristic status.

BLE P2P application on ST BLE ToolBox