J-Link STM32 Utility
The STM32 Utility will be discontinued as of 01.01.2026. After this date, it will no longer receive updates or support. Please refer to #Discontinuation for more information.
J-Link STM32 Unlock (JLinkSTM32.exe) is a free command line based tool which can be used with STM32 devices, to disable the hardware watchdog (activated by programming the option bytes). Additionally, on connect, it unsecures a read-protected STM32 device by re-programming the option bytes to factory defaults. The J-Link STM32 Unlock utility is part of the J-Link Software and Documentation Pack, which is available for download on the SEGGER webpage.
Unsecuring a secured device will cause a mass erase of the flash memory.
Discontinuation
The STM32 Utility will be discontinued as of 01.01.2026. After this date, it will no longer receive updates or support.
SEGGER will migrate the functionality of the STM32 Utility to the Device Provisioner.
Please refer to the Migration guide for instructions on transitioning to the Device Provisioner.
If you are missing any functionality from the STM32 Utility in the Device Provisioner, or if you encounter difficulties during the transition, please contact us through one of our support channels.
Migration guide
The functionality of the STM32 Utility can be fully replaced using the Device Provisioner in combination with custom J-Link Script files.
SEGGER will gradually migrate the unlock functionality for all supported STM32 families natively into the Device Provisioner, eliminating the need for custom script files.
The following table shows which device families are already natively supported:
| Family | Supported | Link |
|---|---|---|
| STM32C0xxxx |  |
|
| STM32F0xxxx |  |
ST_STM32F0_Option_Bytes_Unlock |
| STM32F1xxxx | |
ST_STM32F1_Option_Bytes_Unlock |
| STM32F2xxxx | |
ST_STM32F2_Option_Bytes_Unlock |
| STM32F3xxxx | |
ST_STM32F3_Option_Bytes_Unlock |
| STM32F4xxxx | |
ST_STM32F4_Option_Bytes_Unlock |
| STM32F72xxx | |
|
| STM32F74xxx | |
|
| STM32F76xxx | |
|
| STM32G0x0xx | |
|
| STM32G0x1xx | |
|
| STM32G4xxxx | |
|
| STM32H743_5 | |
|
| STM32H745_4 | |
|
| STM32H7A3_B | |
|
| STM32L0xxxx | |
|
| STM32L1xxxx | |
|
| STM32L4xxxx | |
|
| STM32L5xxxx | |
|
| STM32U5xxxx | |
|
| STM32WBxxxx | |
|
| STM32WLxxxx | |
If your device family is not yet natively supported, you can:
- Contact us via one of our support channels, or
- Create a custom J-Link Script file for the Device Provisioner.
For details on how to use the Device Provisioner, see: https://kb.segger.com/Device_Provisioner#Usage
Migration example
Using JLinkSTM32 Utility:
JLinkSTM32.exe -SetDeviceFamily STM32F0xxxx
Using Device Provisioner:
DevPro.exe -operation PerformUnlock -if SWD -speed 4000 -ScriptFile PCode_DevPro_ST_STM32F0.pex
Command Line Options
The following command line options can be passed to the J-Link STM32 Unlock utility.
| Command line option | Explanation |
|---|---|
| -IP | Selects IP as host interface to connect to J-Link. Default host interface is USB. |
| -SelectEmuBySN | See -USB |
| -USB | Connects to a J-Link with a specific S/N over USB |
| -Speed | Starts the J-Link STM32 Unlock Utility with a given initial interface speed. |
| -SetPowerTarget | Enables target power supply via pin 19. |
| -SetDeviceFamily | Specifies a device family |
| -Exit | J-Link STM32 Unlock will close automatically |
-IP
Selects IP as host interface to connect to J-Link. Default host interface is USB.
Syntax
-IP <IPAddr>
Example
JLinkSTM32.exe -IP 192.168.1.17
Additional information
To select from a list of all available emulators on Ethernet, please use * as <IPAddr>.
-USB
Connect to a J-Link with a specific serial number via USB. Useful if multiple J-Links are connected to the same PC.
Syntax
-USB <SerialNo>
Example
JLinkSTM32.exe -USB 580011111
-Speed
Starts J-Link STM32 Unlock Utility with a given initial speed. Available parameters are "adaptive", "auto" or a freely selectable integer value in kHz. It is recommended to use either a fixed speed or, if it is available on the target, adaptive speeds. Default interface speed is 1000 kHz.
Syntax
-Speed <Speed_kHz>
Example
-Speed 1000
-SetPowerTarget
The connected debug probe will power the target via pin 19 of the debug connector.
Syntax
-SetPowerTarget <Mode>
Example
JLinkSTM32.exe -SetPowerTarget 1
-SetDeviceFamily
This command allows to specify a device family, so that no user input is required to start the unlocking process.
Syntax
-SetDeviceFamily <Parameter>
Parameter
There are two different options to specify the device family to be used:
- By passing the corresponding list index (ID) of the specific family.
- By passing the corresponding device string of the specific family.
| ID | Device string | Device family |
|---|---|---|
| 1 | STM32F0xxxx | STM32F0xxxx |
| 2 | STM32F1xxxx | STM32F1xxxx |
| 3 | STM32F2xxxx | STM32F2xxxx |
| 4 | STM32F3xxxx | STM32F3xxxx |
| 5 | STM32F4xxxx | STM32F4xxxx |
| 6 | STM32F72xxx, STM32F73xxx | STM32F72xxx, STM32F73xxx |
| 7 | STM32F74xxx, STM32F75xxx | STM32F74xxx, STM32F75xxx |
| 8 | STM32F76xxx, STM32F77xxx | STM32F76xxx, STM32F77xxx |
| 9 | STM32G0x0xx | STM32G0x0xx |
| 10 | STM32G0x1xx | STM32G0x1xx |
| 11 | STM32G4xxxx | STM32G4xxxx |
| 12 | STM32H743_53_50 | STM32H743, STM32H750, STM32H753 |
| 13 | STM32H745_47_55_57 | STM32H745, STM32H747, STM32H755, STM32H757 |
| 14 | STM32L0xxxx | STM32L0xxxx |
| 15 | STM32L1xxxx | STM32L1xxxx |
| 16 | STM32L4xxxx | STM32L4xxxx |
| 17 | STM32L5xxxx | STM32L5xxxx |
| 18 | STM32U5xxxx | STM32U5xxxx |
| 19 | STM32WBxxxx | STM32WBxxxx |
| 20 | STM32WLxxxx | STM32WLxxxx |
Example
JLinkSTM32.exe -SetDeviceFamily 10 // Selects STM32L1 series JLinkSTM32.exe -SetDeviceFamily STM32F2xxxx // Selects STM32F2 series
-Exit
In general, the J-Link STM32 utility waits at the end of the unlock process for any user input before application closes. This option allows to skip this step, so that the utility closes automatically.
Syntax
-Exit <Mode>
Example
JLinkSTM32.exe -Exit 1 // J-Link STM32 utility closes automatically