STM32WBA Bluetooth® LE – Health Thermometer Sensor

Revision as of 16:34, 21 March 2023 by Registered User

1. Health Thermometer Profile

Health Thermometer Profile (HTP) [1] is a Generic Attribute Profile (GATT) based low-energy profile defined by the Bluetooth® Special Interest Group.[2]
Health Thermometer Profile is a combination of a Health Thermometer Collector and a Health Thermometer Sensor to connect and exchange data in different applications.
The Health Thermometer Sensor:

  • Measures the temperature and exposes it via the Health Thermometer Service[3]
  • Contains the Device Information Service to be identified by the remote device
  • Is the GATT server

The Health Thermometer Collector:

  • Accesses the information exposed by the Health Thermometer Sensor and can for example display it to the end user or store it on nonvolatile memory for later analysis.
  • Is the GATT client

This wiki page is the description of the Health Thermometer Sensor project provided within the STM32CubeWBA MCU Package[4]

Bluetooth® LE Health Thermometer Profile & STM32WBA
Connectivity WBA HT Profile.png

The table below describes the structure of Health Thermometer Sensor services:

Bluetooth® LE Health Thermometer Service specification
Service Characteristic Property UUID size
Health Thermometer Service 0x1809
Temperature Measurement Indicate 0x2A1C 13
Temperature Type Read 0x2A1D 1
Intermediate Temperature Notify 0x2A1E 13
Measurement Interval Read,Write,Indicate 0x2A21 2
Device Information Service 0x180A
Manufacturer Name String Read 0x2A29 32
Model Number String Read 0x2A24 32
System ID Read 0x2A23 8

Health Thermometer is exported as a Service:

  • Temperature Measurement characteristic (TEMM):
Sends a temperature measurement, and updates related flags.
  • Temperature Type characteristic (MNBS):
One of two methods used to describe the type of temperature measurement in relation to the location on the human body where the temperature was measured.
  • Intermediate Temperature characteristic (INT):
Sends intermediate temperature values to a device for display purposes while the measurement is in progress.
  • Measurement Interval characteristic (MEI):
Enables and controls the interval between consecutive temperature measurements.

Device Information (DIS) is exported as a Service:

  • Manufacturer Name String characteristic (MANS):
Name of the manufacturer of the device.
  • Model Number String characteristic (MONS):
Model number assigned by the device vendor.
  • System ID characteristic (SYID): 
Structure containing an Organizationally Unique Identifier (OUI) followed by a manufacturer-defined identifier and is unique for each individual instance of the product.
Example of flow diagram between STM32WBA & ST BLE Toolbox
STM32WBA HT Flow Diagram

1.1. Advertising data

At start up, Health Thermometer application starts advertising with an interval of approximatively 80-100ms.
Data advertised are composed as follows:

HealthThermometer Advertising packet
Description Length AD Type Value
Device Name 6 0x09 HT_XX (XX: last byte of BD address)
Service UUID 3 0x03 0x1809 (HTS)
Manufacturer Data 15 0xFF See table below
Flags 2 0x01 0x06
(GeneralDiscoverable, BrEdrNotSupported)

Manufacturer data are encoded following 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 0x8B Nucleo-WBA 0x00 0x00 0x00 0x00 0x08E12Axxxx

2. Requirements

2.1. Software and system requirements

The following list contains the required software as well as the required minimum IDE version:

  • IAR Embedded Workbench for ARM (EWARM) toolchain V9.20.1, plus a patch available in WBA Firmware Package: STM32Cube_FW_WBA_Vx.x.x/Utilities/PC_Software/
  • RealView Microcontroller Development Kit (MDK-ARM) toolchain V5.37, plus a patch available in WBA Firmware package: STM32Cube_FW_WBA_Vx.x.x/Utilities/PC_Software/
  • STM32CubeIDE toolchain V1.12.0 [5].

The following programmer software is required to flash the board with an already generated binary:

  • STM32CubeProgrammer[6]

2.2. Hardware requirements

NUCLEO-WBA52CG[7] is necessary to install the application.

Hardware platform illustration

2.3. Compatible collector applications

The STM32CubeWBA Health Thermometer Sensor project is compatible with the following collectors:

3. STM32WBA Health Thermometer Sensor example description

3.1. Project directory

The "BLE_HealthThermometer" application is available by downloading STM32CubeWBA MCU Package[4].

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 illustrating the most important parts:

Health Thermometer project structure
Connectivity WBA HealthThermo Archi.png
Connectivity yellow box.png
Main applicative part files
Connectivity blue box.png
Bluetooth® LE Stack API Interface
Connectivity dark blue box.png
Services management
Connectivity green box.png
System commands
Connectivity pink box.png
Transport Layer Interface

WARNING: Do not modify the files in Middlewares folder

3.2.2. Application initialization

The different steps of the application initialization are described below:

Health Thermometer project initialization
Connectivity WBA HealthThermo Initialization.png
  • Initialize the system (HAL, clocks, peripherals)
  • Infinite loop for run mode
  • Initialize the BSP, Power Mode, trace, memory manager, NVM
  • Wait for initialization done
  • Initialize the Bluetooth® LE Host Stack
  • Initialize the Bluetooth® LE GATT level
  • Initialize the Bluetooth® LE GAP level
  • Reset the number of registered handler
  • Initialize the context
  • Manage Health Thermometer Service notification
  • Register Service Handler
  • Update services and characteristics

3.2.3. GAP and GATT initialization and interaction

Health Thermometer Sensor software module interaction
Connectivity WBA HealtThermo module interaction with puces.png

and puce4.png The Bluetooth® Low Energy Health Thermometer 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 SVCCTL_Init() - svc_ctl.c
  • Manage the GAP event - SVCCTL_App_Notification()
    • HCI_LE_CONNECTION_COMPLETE - provides information of the connection interval, slave latency, supervision timeout
    • HCI_LE_CONNECTION_UPDATE_COMPLETE- provides the new information of the connection
    • HCI_DISCONNECTION_COMPLETE - informs the application about the link disconnection and the reason

The Services management is done by the service controller, svc_ctl.c

  • Initialize the number of registered handler - SVCCTL_Init()
  • Manage events - SVCCTL_UserEvtRx()- from the Bluetooth® Low Energy Host Stack and redirect them to the gap event handler - SVCCTL_App_Notification

The application level of the Health Thermometer is done with hts_app.c:

  • Initialization of the services:
    • Health Thermometer Service - HTS_Init() - hts.c
  • Initialization of the context of the application
  • Receive notification from the Health Thermometer Service - HTS_Notification()
  • When temperature measurement characteristics are enabled by remote, simulate the temperature measurement every second (HTS_APP_Measurement) and increase the energy expended to transfer to the remote device (collector) - HTS_UpdateValue()

The Health Thermometer Service hts.c manages the specification of the service:

  • Service Init - HTS_Init()
    • Register Health Thermometer Event Handle to Service Controller - SVCCTL_RegisterSvcHandler(HTS_EventHandler);
    • Initialize Service UUID – add Health Thermometer service as Primary services
      • Initialize Temperature measurement (TEMM) characteristic
      • Initialize Temperature Type (MNBS) characteristic
      • Initialize Intermediate Temperature (INT) characteristic
      • Initialize Measurement Interval (MEI) characteristic
  • Manage the GATT event from Bluetooth® Low Energy Stack - HTS_EventHandler()
      • Reception of a Write Command: Measurement Interval Characterictic Value
        • Send an aci_gatt_write_response() with an OK or KO status.
      • Reception of an attribute modification - Temperature Measurement Value : ENABLE or DISABLE Indication
        • Notify application of the Measurement Notification - HTS_Notification(HTS_TEMM_INDICATE_ENABLED/DISABLED_EVT)
      • Reception of an attribute modification - Intermediate Temperature Value : ENABLE or DISABLE Notification
        • Notify application of the Measurement Notification - HTS_Notification(HTS_INT_NOTIFY_ENABLED/DISABLED_EVT)
      • Reception of an attribute modification - Measurement Interval Value : ENABLE or DISABLE Indication
        • Notify application of the Measurement Notification - HTS_Notification(HTS_MEI_INDICATE_ENABLED/DISABLED_EVT)

3.3. How to use the Bluetooth® Low Energy Health Thermometer application

Once the Bluetooth® Low Energy Health Thermometer application is installed on the STM32WBA platform, launch the ST BLE ToolBox smartphone application.

Then, scan and connect the device called HT_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 Health Thermometer icon):

  • Intermediate temperature notification is provided to remote every 1 s.
  • Temperature measurement indication is provided to remote every 10 s.

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)

Health Thermometer - Initialization phase Connected Phase
==>> Start Ble_Hci_Gap_Gatt_Init function
  Success: hci_reset command
  Success: aci_hal_write_config_data command - 
  Public Bluetooth Address: 00:80:e1:2a:7c:ea
  Success: aci_hal_write_config_data command - 
  Success: aci_hal_write_config_data command - 
  Success: aci_hal_set_tx_power_level command
  Success: aci_gatt_init command
  Success: aci_gap_init command
  Success: aci_gatt_update_char_value - Device Name
  Success: aci_gatt_update_char_value - Appearance
  Success: hci_le_set_default_phy command
  Success: aci_gap_set_io_capability command
  Success: aci_gap_set_authentication_requirement command
  Success: aci_gap_configure_whitelist command
==>> End Ble_Hci_Gap_Gatt_Init function

Services and Characteristics creation
  Success: aci_gatt_add_service command: DIS
  Success: aci_gatt_add_char command   : MANS
  Success: aci_gatt_add_char command   : MONS
  Success: aci_gatt_add_char command   : SYID
  Success: aci_gatt_update_char_value MANS command
  Success: aci_gatt_update_char_value MONS command
  Success: aci_gatt_add_service command: HTS
  Success: aci_gatt_add_char command   : TEMM
  Success: aci_gatt_add_char command   : MNBS
  Success: aci_gatt_add_char command   : INT
  Success: aci_gatt_add_char command   : MEI
  Success: aci_gatt_update_char_value MEI command
End of Services and Characteristics creation

==>> aci_gap_set_discoverable - Success
==>> Success: Start Advertising
    Connection handle: 0x0001
     - Connection established with @:5f:6e:a2:95:0d:a5
     - Connection Interval:   48.75 ms
     - Connection latency:    0
     - Supervision Timeout: 5000 ms
     - Connection Interval:   7.50 ms
     - Connection latency:    0
     - Supervision Timeout:   5000 ms
     - Connection Interval:   48.75 ms
     - Connection latency:    0
     - Supervision Timeout:   5000 ms

4. References