STM32WBA Bluetooth® LE – Health Thermometer Sensor

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 Hardware requirements

For software and hardware requirements refer to STM32WBA Build BLE Project wiki page.

2.2. 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