How to write option bytes in production?

[EStei.3]

Hi,

i'm currently trying to find a suitable way to programm options bytes in production.

The boards are flashed using a J-Link and we would not like to switch to ST-Link.

Is it possible to simply add the option bytes to our binary?

I guess at least some script would be necessary for unlocking the the write access for the option bytes.

Any help is appreciated!

BR

[Florian LR]

Hi @EStei.3​,

You can program your option bytes within the code that you flash on your boards.

In order to do that, you have to create first the programming option structure :

FLASH_OBProgramInitTypeDef OBInitStruct;

You are right about the need to unlock the write access for the option bytes.

You need to unlock the flash, and then the option bytes using :

HAL_FLASH_Unlock();
HAL_FLASH_OB_Unlock();

Then you can fill your OBInitStruct with the options you need (you can find the detail of the possible options and the values you can attribute in the stm32XXxx_hal_flash.h or stm32XXxx_hal_flash_ex.h file, depending on what product you are using.

You can now program the selected option bytes using :

HAL_FLASHEx_OBProgram(&OBInitStruct);

Then you lock what you unlocked earlier using HAL_FLASH_OB_Lock()  and HAL_FLASH_Lock().

Finally, you start the option bytes load operation using :

HAL_FLASH_OB_Launch(); 

This should help you program your option bytes directly into your code.

Best regards,

Florian LR

[Pavel A.]

Ask on the Segger J-Flash forum, perhaps they have some utility for STM32 option bytes.

[EStei.3]

Thanks for the response!

Unfortunately our board won't boot on power up unless the option bytes are set correctly because there is a pull up on the boot pin.

I could probably add the code as you described and somehow start the firmware using the debugger but I was looking for a way to directly set the option bytes using the debugger.

Are there any suggestions on how to set the option bytes with any generic debugger?

[Tesla DeLorean]

The STM32 model isn't mentioned

If you have serial port connectivity, perhaps use the system loader, see AN2606 for pins, AN3155 for protocol

[EStei.3]

Thanks for the response!

I didn't mention the STM32 model on purpose because the problem is generic and independent to the exact controller.

Unfortunately there is no serial port connectivity on the board.

[Tesla DeLorean]

In future designs perhaps consider getting some connectivity per AN2606 so you can establish test station connectivity with a low cost, low complexity interface. Pins for a UART, NRST, BOOT0 can be facilitated by Test Points, Edge Castellations, or break-off sections of board when separated from panel.