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AN5247
User Manual
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ST AN5247 User Manual

AN5247
Application note
Over-the-air application and wireless firmware update for
STM32WB Series microcontrollers
Introduction
This application can update the user application, the wireless firmware and the firmware upgrade service.
®
Low Energy (BLE) connection. It explains how to use the OTA
February 2021 AN5247 Rev 3 1/36
www.st.com
1
Contents AN5247
Contents
1 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Reference documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 OTA application on STM32WB devices . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Over-the-air firmware update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1.1 Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1.2 OTA application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.3 Memory architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.4 User application update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.5 Wireless firmware update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 BLE service and characteristics for firmware update . . . . . . . . . . . . . . . . 13
3.2.1 BLE application – Reboot request characteristics . . . . . . . . . . . . . . . . . 13
3.2.2 OTA application - Service and characteristics . . . . . . . . . . . . . . . . . . . . 15
3.2.3 Advertising . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3 Flow description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4 Wireless and FUS update procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.5 Updater clients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.5.1 ST BLE Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.5.2 STM32CubeMonitor-RF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4 OTA step by step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1 Project setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1.1 User applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1.2 OTA application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.2 Firmware update with ST BLE Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.2.1 Device connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.2.2 Update of user application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.2.3 Update of wireless stack or FUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3 Firmware update with STM32CubeMonitor-RF . . . . . . . . . . . . . . . . . . . . 31
4.3.1 Transparent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.2 Update of the user application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
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AN5247 Contents
6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
AN5247 Rev 3 3/36
3
List of tables AN5247
List of tables
Table 1. Reboot request characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 2. OTA Service and characteristics declaration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 3. AD structure - Main . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 4. AD structure - Manufacturer specific field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 5. AD structure – Group B features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 6. Services and characteristics of example applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 7. Example (device Bluetooth MAC address = 80:E1:25:00:50:D6) . . . . . . . . . . . . . . . . . . . . 25
Table 8. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4/36 AN5247 Rev 3
AN5247 List of figures
List of figures
Figure 1. STM32WB dual core FW architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 2. Update of STM32WB firmware through BLE connection . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 3. OTA procedure sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 4. Simplified memory map of applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 5. BLE application and wireless firmware architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 6. User application update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 7. wireless firmware update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 8. OTA reboot characteristic added in BLE user application . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 9. OTA dataflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 10. ST BLE Sensor mobile application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 11. STM32CubeMonitor-RF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 12. STM32CubeMonitor-RF with USB dongle in transparent mode. . . . . . . . . . . . . . . . . . . . . 20
Figure 13. Applicative projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 14. User application update - Use case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 15. Peer-to-peer server device detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 16. Peer-to-peer application / LED switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 17. Firmware update ST BLE Sensor panel and OTA service detected. . . . . . . . . . . . . . . . . . 28
Figure 18. Download of new application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 19. Heart rate profile after update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 20. Update of wireless stack or FUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 21. USB Dongle programming in USB DFU mode with STM32CubeProgrammer. . . . . . . . . . 32
Figure 22. Update of the user application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 23. Wireless or FUS update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
AN5247 Rev 3 5/36
5
Glossary AN5247

1 Glossary

BLE Bluetooth® Low Energy (Bluetooth® standard)
CPU1 Cortex
CPU2 Cortex
IDE Integrated development environment
IPCC Inter-processor communication controller
FUS Firmware update service
OTA Over-the-air firmware update
SBRSA Option byte - Secure backup RAM start address
SBRV Option byte - Secure boot reset vector
SFSA Option byte - Secure Flash memory start address
SIG Bluetooth
SNBRSA Option byte - Secure non-backup RAM start address
®
M4 (executes user application)
®
M0+ (executes FUS and wireless firmware)
®
special interest group

2 Reference documents

[1] RM0434: Multiprotocol wireless 32-bit MCU Arm
Bluetooth
[2]
AN5185: STM32WB ST firmware upgrade services
[3]
UM2288: STM32CubeMonitor-RF software tool for wireless performance
measurements
All these documents are available on www.st.com.
®
Low-Energy and 802.15.4 radio solution
®
-based Cortex®-M4 with FPU,
6/36 AN5247 Rev 3
AN5247 OTA application on STM32WB devices
MS51778V3
Wireless stack FUS
BLE user
application
OTA
application
CPU2
CPU1
Updatable by
OTA
Not updatable
by OTA

3 OTA application on STM32WB devices

3.1 Over-the-air firmware update

3.1.1 Principle

Updating firmware during device lifetime is mandatory to guarantee state-of-art performance, to update the application with new features or corrected patches, and to keep the highest security level.
User application, wireless firmware and FUS update
The STM32WB Series microcontrollers are based on a dual Arm
®(a)
core.
The user application runs on CPU1 (Cortex® M4), while wireless firmware and FUS run on CPU2 (Cortex
As wireless and FUS are delivered in encrypted format, their update procedure relies on the STM
32WB secure firmware for decryption and installation in the protected area of the Flash
memory.
®
M0+). The three applications can be updated independently.
Figure 1. STM32WB dual core FW architecture
Over the air
Update of firmware can be done thanks to typical physical links such as USB, UART or I2C but this procedure requires a physical access with specific connectors on the device. Thanks to OTA it is possible to remotely update the firmware by using a wireless connection. In this application note, the wireless connection uses the BLE protocol.
a. Arm is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.
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OTA application on STM32WB devices AN5247
Update clients
Update procedure follows a client/server architecture. It is initiated by an external client and the device acts as a server, responding to the request by installing the new firmware.
In this application note two examples (see Figure 2) of BLE-based OTA clients provided by STMicroelectronics are presented:
ST BLE Sensor: a mobile application for Android™ or iOS devices
STMCubeMonitor-RF: a PC tool communicating with a BLE USE dongle configured in
HCI transparent mode
Figure 2. Update of STM32WB firmware through BLE connection
8/36 AN5247 Rev 3
AN5247 OTA application on STM32WB devices
MS51780V1
System reset
OTA request?
Application
update service
Wireless
update service
RSS wireless
update service
OTA client User app
3 Reboot service
2 OTA request
4 Yes
1 No
6 User FW or
wireless stack
update request
7 Update
5 OTA app active
OTA appOTA client

3.1.2 OTA application

OTA application is designed as a standalone application with BLE services for managing firmware transfer on client request, and its installation at the right place in the Flash memory. It is active and executed by CPU1 after an OTA request has been received by the user application.
The sequence is shown in Figure 3, where the numbers in red indicate the different stages.
Initial state is the user application running (1). When an OTA request is received (2), a system reset is triggered (3) and the OTA application becomes active (4) listening for client requests (5). Different services are provided for the update of wireless firmware or user application (6 and 7).
Figure 3. OTA procedure sequence
Note: With this firmware architecture, the current user application is responsible for receiving OTA
requests for both the user application and the wireless firmware. This is the entry point of the procedure. OTA application then communicates with the client to update either one or the other firmware.

3.1.3 Memory architecture

The Flash memory of STM32WB is split in two parts, a user and a secure one. The user part is accessible by CPU1 and contains the OTA application as well as the user application code and data. The secure part is accessible by CPU2 only, and contains FUS and the wireless firmware. This part is not accessible by the debug port, by the user application or by the bootloader. The boundary between the two areas is given by the option byte SFSA, the memory above is secure (see firmware size, it is adjusted during the install procedure.
Figure 4). The SFSA value depends on the wireless
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OTA application on STM32WB devices AN5247
MS51781V2
OTA application
User data
User application
Free area
Wireless FW
FUS
Flash memory
SFSA
CPU2
CPU1
0x080000000
0x080FFFFF
Secure User part
The location of firmware involved on the OTA procedure is shown in Figure 4.
Figure 4. Simplified memory map of applications
FUS
FUS is stored at the top of the Flash memory. It embeds the secure firmware for wireless firmware decryption and authentication. It also offers a secure storage for cryptographic keys. Refer to
[2] for a detailed description of its features.
Wireless firmware
It is stored just below FUS. This firmware drives the RF part of the MCU. Several protocols are supported: full BLE stack, BLE HCI only layer, Thread MTD, Thread FTD, concurrent mode (BLE + Thread FTD) and MAC 802.15.4 (low-level access to RF MAC). All stacks are available on www.st.com.
For BLE, the stack implements the real-time aspects. It contains the LE controller and LE host needed to manage all real time link layer and radio PHY interaction (
Figure 5).
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AN5247 OTA application on STM32WB devices
Figure 5. BLE application and wireless firmware architecture
User application and data
This is the main user application. It is the applicative part of the device, implementing the BLE profiles and services relying on a wireless protocol. Communication between the user application and the wireless part is done through a mailbox system implemented thanks to the SRAM2 and IPCC hardware blocks ( application in the user Flash memory.
For convenience, a sector for application data not be erased during firmware update can be reserved between the two applications.
Note: A free area of the Flash memory must be available for the new wireless image download in
case of updates.
AN5247 Rev 3 11/36
Figure 5). It is stored just above the OTA
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