STM32WBA Bluetooth® Low Energy – human interface device

1. Human interface device over generic attribute profile (GATT)

Human interface device over GATT profile (HOGP) is a low-energy, generic-attribute-profile-based profile defined by the Bluetooth^® special interest group (SIG)

This profile is an adaptation of the USB human interface device (HID) specification to operate over a Bluetooth^® Low Energy wireless link. This profile operates on Bluetooth^® Low Energy transport only.

The profile defines three roles:

• The human interface device (HID) is a GATT server.
• The boot host is a GATT client.
• The report host is a GATT client.

Bluetooth^® Low Energy devices are not supported by PC BIOS, because the Bluetooth^® Low Energy stack and drivers are not loaded yet at this point, so the boot host role cannot be used with clients like PCs, smartphones, or tablets.

Bluetooth® Low Energy HOGP: report host and HID device

The report host supports the scan client role of the scan parameters profile.

The HID device has:

• One or more instances of the HID service.
• One or more instances of the battery service.
• A single instance of the device information service.
• Optionally, one instance of the scan parameters service as part of the scan server role of the scan parameters profile.
• Optionally, a single or multiple instances of other services.

This wiki page describes the HID mouse project, provided with the STM32CubeWBA MCU Package

Bluetooth® Low Energy HOGP mouse profile with STM32WBA

The table below describes the structure of HOGP services:

Bluetooth® Low Energy HOGP profile specification
Service Characteristic Mode UUID Size HID service 0x1812 Report Input: read/notify 0x2A4D 80 Report Output: read/write/write without response 0x2A4D 80 Report Feature: read/write 0x2A4D 80 HID information Read 0x2A4A 4 HID control point Write without response 0x2A4C 1 Device information service 0x180A - - PnP ID Read 0x2A50 32 Battery service 0x180F Battery level Read 0x2A19 1

The table below describes the HID report characteristic descriptors:

Bluetooth® Low Energy HID report characteristic descriptors specification
Characteristic name Descriptor name UUID Size Report 0x2A4D Client characteristic configuration descriptor​ 0x2902 1 Report reference descriptor 0x2908 2

The table below describes the battery level characteristic descriptor:

Bluetooth® Low Energy battery level characteristic descriptor specification
Characteristic name Descriptor name UUID Size Battery level 0x2A19 Client characteristic configuration descriptor​ 0x2902 1

HOGP is a combination of a HID device and a report host to connect and exchange data in different applications.

The generic access profile (GAP) defines and manages advertising and connection.

Report host central device and HID peripheral device

The generic attribute profile (GATT) defines and manages in/out data exchanges.

Report host GATT client device and HID GATT service device

Examples of an HID flow diagram between a STM32WBA55G-DK1 board and a Bluetooth® Low Energy PC or Bluetooth® Low Energy smartphone

1.1. STMicroelectronics manufacturer advertising data

At startup, HID device application starts fast advertising (80ms/100ms), including the STMicroelectronics manufacturer advertising elements described below:

HID device STMicroelectronics manufacturer advertising data
0 1 2-3 4 5 6 7 8 9 10-15 Length Manufacturer ID Company BlueSTSDK Version Device ID Firmware ID Option 1 Option 2 Option 3 Device Address HID Device 0x0F 0xFF 0x0030 STMicro 0x02 0x8C DK-WBA 0x8B - HID Device 0x00 0x00 0x00 0x08E12Axxxx

Advertising is switched to Low-power advertising (1s/2.5s) after 60 seconds.

2. Requirements

2.1. Software and system requirements

The following list contains the required software and minimum IDE versions:

• IAR Embedded Workbench for ARM (EWARM) toolchain V9.20.1, with a patch available in the STM32WBA firmware package: STM32Cube_FW_WBA_Vx.x.x/Utilities/PC_Software/EWARMv8_STM32WBAx_V1.3.zip
• RealView Microcontroller Development Kit (MDK-ARM) toolchain V5.38, plus a patch available in the STM32WBA firmware package: STM32Cube_FW_WBA_Vx.x.x/Utilities/PC_Software/Keil.STM32WBAx_DFP.1.3.0.zip
• STM32CubeIDE toolchain V1.14.0

The following programmer software is required to program the board with a pregenerated binary:

• STM32CubeProgrammer

2.2. Hardware requirements

This application requires an STM32WBA55G-DK1 (Discovery Kit) board.

STM32WBA55G-DK1 board

2.3. Collector applications compatible

The STM32CubeWBA HID device project is compatible with the following collectors:

• Smartphone BLE
• PC BLE

3. STM32WBA55G-DK1 HID Device example description

3.1. Project directory

Refer to STM32CubeWBA Bluetooth® LE MCU Package Wiki page for project directory information and how to download the "BLE_HID_Mouse" application.

3.2. Project description

3.2.1. Structure

Below, a software project structure with the most important parts:

HID Mouse project structure
Main applicative part files Services management Bluetooth® Low Energy libraries Link Layer System integration files WARNING: Do not modify the files in Middleware folder

3.2.2. Application initialization

The different steps of the application initialization are described below:

HID Mouse project initialization

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® Low Energy Host Stack. Initialize the Bluetooth® Low Energy GATT level. Initialize the Bluetooth® Low Energy GAP level. Reset the number of registered handlers. Initialize the context. Manage the HID Service notification. Register Service Handler. Update the services and characteristics.

3.2.3. GAP and GATT initialization and interaction

HID Mouse Device software module interaction

and The Bluetooth® Low Energy HID Mouse 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 handlers - 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 HID Mouse Device is done with hids_app.c:

• Initialization of the services:
  • HID Service - HIDS_Init() - hids.c
• Initialization of the context of the application
  • Report Map
  • HID Information - BASE USB HID SPEC VERSION
• Receive notification from the HID Service - HIDS_Notification()
• When Input Report characteristic is enabled by the remote, each update of the mouse position with the joystick (HIDS_APP_UpdateReport) is transfered to the remote device (collector) - HIDS_UpdateValue().

The HID Service hids.c manages the specification of the service:

• Service Init - HIDS_Init()
  • Registers HID Event Handle to Service Controller - SVCCTL_RegisterSvcHandler(HIDS_EventHandler).
  • Initializes Service UUID – add HID service as Primary services.
    • Initializes Report Map characteristic.
    • Initializes HID Information characteristic.
• Manages the GATT event from the Bluetooth® Low Energy Stack - HIDS_EventHandler().
  • ACI_GATT_WRITE_PERMIT_REQ_VSEVT_CODE
    • Reception of a Write Command: HID Control Point Characteristic Value
      • Sending of an aci_gatt_write_response() with an OK or KO status
      • Notification to the application to Suspend or Exit Suspend - HIDS_Notification(HIDS_HCP_WRITE_NO_RESP_EVT)
  • ACI_GATT_ATTRIBUTE_MODIFIED_VSEVT_CODE
    • Reception of an attribute modification - Input Report Characteristics Description Value : ENABLE or DISABLE Notification
      • Notify application of the Input Report Notification - HIDS_Notification(HIDS_NOTIFICATION_ENABLED/DISABLED)

3.2.4. Report Map and Input Report

HID Report Map characteristics should contain the USB HID descriptor specified in the USB HID specification .

An USB HID descriptor is a hard coded array of bytes describing the device’s data packets, including:

• Number of packets supported,
• Packets size,
• Purpose of each byte and bit in the packet.

Example of USB Mouse HID descriptor for a 3 buttons Mouse with X, Y axis and a wheel:

USB Mouse HID descriptor

3 buttons Mouse with X, Y axis and a wheel

All the hard coded bytes are described in the USB HID Usage Tables document. This USB HID descriptor also defines the data structure sent in the associated Reports (Input, Output or Feature).

In this USB Mouse HID descriptor example, you can find:

• Highlighted in green, the definition of 3 buttons represented by the 3 first bits of a byte that can have the boolean state 0 or 1.Bits 0, 1 and 2 represents the states of respectively the left, the middle and the right buttons of the mouse.The remained bits of the byte are unused.
• Highlighted in blue, the definition of 3 bytes for the X, Y axes relative movement and wheel rotation. Each byte represents a signed integer that can take a value comprised between -127 to 127.

Example of the Input Report associated to USB Mouse HID descriptor:

3 buttons Mouse with X, Y axis and a wheel data structure

3.3. How to use the Bluetooth® Low Energy HID Mouse application

Once the Bluetooth® Low Energy HID Mouse application is installed on the STM32WBA55G-DK1 platform, launch a Bluetooth® Low Energy connection on a smartphone or a PC. Then, scan and connect the device called HIDS_XX (where XX is replaced by the last byte of the BD address) to the application.
As shown in the following screenshots for a ANDROID smartphone connection:

Android Bluetooth® Low Energy HID Mouse – How to

Or for a PC connection:

PC Bluetooth® Low Energy HID Mouse – How to

PC Bluetooth® Low Energy HID Mouse – How to

PC Bluetooth® Low Energy HID Mouse – How to
	PC HID CONNECTED

PC Bluetooth® Low Energy HID Mouse – How to

Once the Bluetooth® Low Energy connection is established and the notification enabled by the smartphone or the PC, HID Input Report is sent each time an action is performed on the STM32WBA55G-DK1 joystick .

STM32WBA55G-DK1 joystick

• Action on Up, down, left and right direction sends an Input report containing a relative position.
• Press on the joystick on neutral position sends an input report containing the state of the left button.

3.4. Low-power optimization

The project is delivered with the full system low-power disabled:

• debug trace enabled
• debugger enabled even in Low Power Mode

It is possible to enable/disable the low-power feature within app_conf.h.

/******************************************************************************
 * Low Power
 *
 *  When CFG_LPM_LEVEL is set to:
 *   - 0 : Low Power Mode is not activated, RUN mode will be used.
 *   - 1 : Low power active, the one selected with CFG_LPM_STDBY_SUPPORTED
 *   - 2 : In addition, force to disable modules to reach lowest power figures.
 *
 * When CFG_LPM_STDBY_SUPPORTED is set to:
 *   - 1 : Standby is used as low power mode.
 *   - 0 : Standby is not used, so stop mode 1 is used as low power mode.
 *
 ******************************************************************************/
#define CFG_LPM_LEVEL            (0)
#define CFG_LPM_STDBY_SUPPORTED  (0)

3.5. 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:

/*****************************************************************************
 * Logs
 *
 * Applications must call LOG_INFO_APP for logs.
 * By default, CFG_LOG_INSERT_TIME_STAMP_INSIDE_THE_TRACE is set to 0.
 * As a result, there is no time stamp insertion inside the logs.
 *
 * For advanced log use cases, see the log_module.h file.
 * This file is customizable, you can create new verbose levels and log regions.
 *****************************************************************************/
/**
 * Enable or disable LOG over UART in the application.
 * Low power level(CFG_LPM_LEVEL) above 1 will disable LOG.
 * Standby low power mode(CFG_LPM_STDBY_SUPPORTED) will disable LOG.
 */
#define CFG_LOG_SUPPORTED           (1U)

/* Configure Log display settings */
#define CFG_LOG_INSERT_COLOR_INSIDE_THE_TRACE       (0U)
#define CFG_LOG_INSERT_TIME_STAMP_INSIDE_THE_TRACE  (0U)
#define CFG_LOG_INSERT_EOL_INSIDE_THE_TRACE         (0U)

/* macro ensuring retrocompatibility with old applications */
#define APP_DBG                     LOG_INFO_APP
#define APP_DBG_MSG                 LOG_INFO_APP

A debugger can also be supported by enabling it within app_conf.h as described below:

/******************************************************************************
 * Debugger
 *
 *  When CFG_DEBUGGER_LEVEL is set to:
 *   - 0 : No Debugger available, SWD/JTAG pins are disabled.
 *   - 1 : Debugger available in RUN mode only.
 *   - 2 : Debugger available in low power mode.
 *
 ******************************************************************************/
#define CFG_DEBUGGER_LEVEL           (2)

HID Mouse - Initialization phase

Connected Phase

Start of CRC computation End of CRC computation, value : 26349 Start of CRC computation End of CRC computation, value : 26349==>> Start Ble_Hci_Gap_Gatt_Init function Success: aci_hal_write_config_data command - CONFIG_DATA_PUBADDR_OFFSET Public Bluetooth Address: 00:80:e1:2a:ff:36 Success: aci_hal_write_config_data command - CONFIG_DATA_IR_OFFSET Success: aci_hal_write_config_data command - CONFIG_DATA_ER_OFFSET 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: HIDS Success: aci_gatt_add_char command : INPUTREP Success: aci_gatt_add_char_desc command : INPUT REP REF DESC on handle 0x10 Success: aci_gatt_add_char command : REM Success: aci_gatt_add_char command : HII Success: aci_gatt_add_char command : HCP Success: aci_gatt_update_char_value REM command Success: aci_gatt_update_char_value HII command Success: aci_gatt_add_service command: DIS Success: aci_gatt_add_char command : PNI Success: aci_gatt_update_char_value PNI command Success: aci_gatt_add_service command: BAS Success: aci_gatt_add_char command : BAL Success: aci_gatt_update_char_value BAL command End of Services and Characteristics creation ==>> aci_gap_set_discoverable - Success ==>> Success: Start Advertising

>>== HCI_LE_CONNECTION_COMPLETE_SUBEVT_CODE - Connection handle: 0x0001 - Connection established with @:65:92:b8:52:36:4b - Connection Interval: 45.00 ms - Connection latency: 0 - Supervision Timeout: 5000 ms >>== ACI_GAP_NUMERIC_COMPARISON_VALUE_VSEVT_CODE - numeric_value = 447414 - Hex_value = 6d3b6 ==>> aci_gap_numeric_comparison_value_confirm_yesno : Success SNVMA_Write - Impacted NVM : 1 SNVMA_Write - Pending buffer : 1 FM_Write - Returned value : 0 SNVMA_Write - Flash operation started (Header write request) : 16 SNVMA_Write - Impacted NVM : 1 SNVMA_Write - Pending buffer : 1 SNVMA_Write - Impacted NVM : 1 SNVMA_Write - Pending buffer : 1 FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback >>== ACI_GAP_PAIRING_COMPLETE_VSEVT_CODE - Pairing Success FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation SNVMA_FlashManagerCallback - Flash operation state : SNVMA_HEADER_WRITE FM_Write - Returned value : 0 FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Write operation SNVMA_FlashManagerCallback - Flash operation state : SNVMA_BUFFER_WRITE Start of CRC computation End of CRC computation, value : 48382 FM_Erase - Returned value : 0 FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP - Erase operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window FM_WindowAllowed_Callback FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Time window granted FM_BackgroundProcess - Case FM_BKGND_WINDOWED_FLASHOP - Erase operation SNVMA_FlashManagerCallback - Flash operation state : SNVMA_RETRY_WRITE FM_Write - Returned value : 0 FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP FM_BackgroundProcess - Case FM_BKGND_NOWINDOW_FLASHOP - Write operation FM_BackgroundProcess - Flash operation not complete yet, request a new time window >>== 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 HIDS_REP_NOTIFY_ENABLED_EVT