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The ST STM32WB series devices are heterogeneous dual-core MCUs with a Cortex-M4 for the end-user application and a Cortex-M0 for the BLE stack. The STM32WB series currently consists of 3 sub-families:

  • STM32WBx0
  • STM32WBx5
  • STM32WBxM

Internal flash

The STM32WB device series comes with varying sizes of internal flash up to 1 MB, which is generally supported by J-Link.

Device name Range / Size
STM32WBxxxC 0x0800_0000 - 0x0803_FFFF (256 KB)
STM32WB1xxC 0x0800_0000 - 0x0804_FFFF (320 KB)[1]
STM32WBxxxE 0x0800_0000 - 0x0807_FFFF (512 KB)
STM32WBxxxY 0x0800_0000 - 0x0809_FFFF (640 KB)
STM32WBxxxG 0x0800_0000 - 0x080F_FFFF (1 MB)[2]
  1. The ST STM32WB1x devices are special compared to the other STM32WB devices e.g. the sector size is 2KB instead of 4KB.
  2. Partially used for BLE stack image. The section that is reserved for this purpose is read/write protected.

Concerning STM32WBxxxG (1MB) devices:
A chip erase for these devices will usually fail.

This is because a part of the flash is protected as long as a wireless stack is present, resulting in a write protection error during chip erase.

Option bytes flash

Option byte programming is directly supported by J-Link. Alternatively, option bytes can be programmed via the Flash registers as shown in the ST STM32 main article.


Root Security Service (RSS) and the Firmware Upgrade Service (FUS) are responsible for secure wireless stack updates and encryption key management. This firmware is executed by the secure core (Cortex-M0) and is not accessible by the end user or a debug probe. It is factory installed on any ST STM32WB devices flash memory and is marked as secured. On some STM32WB devices, the last sectors of the user flash are used for the RSS ande Wireless stack (WS), on others, flash outside of the user area is used for this purpose.

  • Before executing any upgrade/erase attempt, please make sure that you are using the latest version of the J-Link Software Pack.
  • The upgrade process and the required steps were extensively reworked/changed with J-Link Software V7.86f.
    This section describes this new, reworked process.

How to update the Wireless Stack

Updating FUS and WS stack can automatically be done with J-Link Commander or J-Flash This section describes how this is done via the following steps:

  1. Acquire Wireless Stack binaries and determine the correct flash address.
  2. Select the device <DeviceName> - FUS in the J-Link Commander or J-Flash.
  3. Download the data file to the correct position, specified by the ST documentation.

Acquire Wireless Stack binaries

The wireless stack binaries can be downloaded from
After downloading:

  • Unpack the package
  • Navigate to STM32Cube_FW_WB_V<Version>\Projects\STM32WB_Copro_Wireless_Binaries\
  • Open Release_Notes.html, which contains information about:
    • The available image options
    • The corresponding binary files and where they should be programmed to

J-Link Commander - Upgrading the image

Open the J-Link commander (%JLinkInstallDir%\JLink.exe) using the following example command line (example for ST STM32WB55RG devices):

  JLink.exe -autoconnect 1 -device "STM32WB55RG - FUS" -if swd -speed 4000
  JLinkExe  -autoconnect 1 -device "STM32WB55RG - FUS" -if swd -speed 4000

After connecting to the MCU successfully, download the image using the LoadFile command, followed by the Exit command. The mandatory reset is issued implicitly by the loadfile command.

loadfile <PathToBinary>\stm32wb5x_BLE_Stack_fw.bin, <Address>
  • Make sure that the Exit step is executed before severing the connection between J-Link and device, as the option bytes are restored during this step.
  • The address the image has to be downloaded to differs depending on the image version, the used device and the selected image option.
Example (STM32WB5xxG, version 1.1.0)
J-Link> loadfile "C:\Users\Fabian\Desktop\STM32Cube_FW_WB_V1.13.0\Projects\STM32WB_Copro_Wireless_Binaries\STM32WB5x\stm32wb5x_BLE_Stack_full_fw.bin" 0x080C7000
J-Link> Exit

J-Flash - Upgrading the image

  1. Create a project for the device you are using (<DeviceName> - FUS)
  2. Add the data file to the project (make sure to select the correct start location of the image, as binary files do not contain address information!)
  3. Important: Check: Options > Project Settings > Production > Actions performed by 'Production Programming' > Disconnect afterwards
  4. Download the image via Target > Production Programming (F7)
  5. Wait for the process to complete (Takes ~30 seconds)

Flasher stand-alone - Upgrading the image

The upgrade process is also supported via Flasher stand-alone programming (since V7.86g). In J-Flash:

  1. Create a J-Flash project as described here
  2. Download the data & config file to Flasher via File > Download config & data file to Flasher
  3. Execute the upgrade by pressing the program button on the Flasher (PROG)

Starting the wireless stack

The following table shows under which conditions the wireless stack will be (re)started and running on disconnect (e.g. closing J-Link Commander).

WS State before connect FUS/WS was updated
after connect
Is WS started
on disconnect
Running NO.png YES.png
Not running NO.png NO.png[1]
Running YES.png YES.png
Not running YES.png YES.png
  1. Only applies if the WS is not manually started by the user during the session. If it was, the state would also be "running".

How to delete the Wireless Stack

The WS is deleted during the "Reset"-step. Thus, triggering a reset will delete the WS. This can be done in different ways.

J-Link Commander

  1. Connect to the device.
  2. Issue the Reset command.
  3. Disconnect to make sure that the boot mode is restored.


  1. Create a project for the device (- FUS!).
  2. Connect to the device. This will implicitly trigger a reset.
  3. Disconnect to make sure that the boot mode is restored.

How to update FUS

Follow the same steps as explained in How to update the Wireless Stack, but with a FUS image instead of a WS image.

  • Once the FUS is updated from the v0.5.3 to v1.0.1 is not possible to reverse RSS or install WS from previous versions. The RSS/FUS can only upload wireless stacks within the same release version.
  • During the FUS upgrade, the WS will be deleted.

How does it work

The process for upgrading the WS/FUS on the ST STM32WBxx with J-Link works by uploading the binary to the flash memory and then by sending an upgrade request to the FUS. This is done using the Inter-Processor Communication Channel (IPCC) via shared tables. The process is described step-by-step below.

To guarantee that the IPCC can be used and the Info table is setup, the device boot mode will be changed during connect to start the device in system boot mode. The boot mode will be restored on disconnect.
  1. Connect:
    • The device is forced to boot in system bootmode via option bytes.
    • FUS is started through IPCC.
  2. Reset: The wireless stack is deleted by issuing the corresponding IPCC command.
  3. Flash program:
    • The upgrade image is programmed to the device flash
    • The upgrade procedure is triggered by issuing the corresponding IPCC command.
    • The wireless stack is started after a successful upgrade.
  4. Disconnect:
    • If no Reset/Download was executed, the WS state will be restored (running/not running).
    • The option bytes are restored to their original values before connect.
The whole process takes around 20 to 30 seconds, depending on the downloaded image.

Sending FUS commands manually

In case a command is not supported out of the box, it has to be sent manually. This can be done via the IPCC mailbox system used for FUS communication. To do so, a connection has to be established via the J-Link Commander.

  • The mailbox buffer addresses depend on the device setup. In the following, the default system bootloader boot mode default locations are used.
  • For a list of available commands and the corresponding responses, please refer to the ST documentation (AN5185).

General sequence

Mem32  0x58000C0C, 1          // Channel 2 (CH2F bit == bit 1) busy? Wait for it to clear. Otherwise, prcoeed.
Write4 0x20030064, 0          // Clear mailbox message header
Write4 0x20030068, 0          // Clear mailbox message buffer
Write4 0x2003006C, <Cmd>      // Write command packet "<Cmd>"
// Optional: Send payload here.
Write4 0x58000C08, 0x20000    // Set CH2F via CH2S (channel 2 data transmit bit)
Write4 0x58000C04, 0xFFFDFFFD // Unmask Channel 2 interrupt (CH2FM & CH2OM)
Mem32  0x58000C0C, 1          // _IPCC_C1TOC2SR Still busy (bit 1 == 1)? => Repeat this until unoccupied (bit 1 == 0).
Mem32  0x20030064, <8+n>      // Read command response: 8 bytes (header + response message) + n bytes payload.

In case a Payload is required for the command, it has to be added after "Send command <Cmd>". The payload contains 0 - 255 bytes:

Write4 0x20030070, <Payload0-3>
Write4 0x20030168, <Payload248-251>
Write1 0x2003016C, <Payload252>
Write1 0x2003016D, <Payload253>
Write1 0x2003016E, <Payload254>

Example - Get FUS state

Mem32  0x58000C0C, 1          // Channel 2 (CH2F bit == bit 1) busy? Wait for it to clear. Otherwise, prcoeed.
Write4 0x20030064, 0          // Clear mailbox message header
Write4 0x20030068, 0          // Clear mailbox message buffer
Write4 0x2003006C, 0x00FC5210 // Write command packet <Type(Command packet) | Command (FUS_GET_STATE) | payload length == 0>.
Write4 0x58000C08, 0x20000    // Set CH2F via CH2S (channel 2 data transmit bit)
Write4 0x58000C04, 0xFFFDFFFD // Unmask Channel 2 interrupt (CH2FM & CH2OM)
Sleep 500                     // Make sure command had enough time. Alternatively wait for C1TOC2SR bit 1 to turn 0.
Mem32 0x20030064, 2           // Read command response: 8 bytes (header + FUS state).
Instead of waiting for the channel to turn unoccupied, we simply wait 500ms in the example. Alternative, wait for C1TOC2SR Channel 2 bit (bit 1) to turn 0.


How does J-Link communicate with the FUS? and performs the Wireless stack upgrade/delete requests?

For the communication with the RSS/FUS, the Inter-Processor Communication Channel (IPCC) is used via shared tables, specified by ST.

Does this mean that the Cortex-M0 is always running the FUS firmware?

No, the FUS firmware is only running when

  • No wireless stack is installed
  • A FUS start request is sent via the IPCC and accepted by FUS.

Can I delete the FUS firmware?

No, the FUS firmware can not be fully deleted. It can only be upgraded.

Evaluation boards

  • TBD