IWDT implementation in threads

[meghasb]

Hi all,

I'm trying to implement the Independent Watchdog Timer (IWDT) on a TrustZone-enabled STM32U5 controller. My goal is to configure and run the IWDT from the Non-Secure (NS) area.

Here’s what I’ve done so far:

• I have an Azure RTOS ThreadX-based application.

• I've created a thread that runs every 10 seconds.

• Inside this thread, I’m initializing the IWDT and then calling HAL_IWDG_Refresh().

• I’ve configured the IWDT for a timeout of 11 seconds.

However, I’m getting a Hard Fault when this thread executes.

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What I'm looking for:

• A working reference or example of IWDT implementation in a ThreadX thread in the Non-Secure area on a TrustZone-enabled STM32 (e.g., STM32U585).

• Guidelines on how and where to initialize the IWDT (Secure vs Non-Secure).

• Any TrustZone-related permission issues I should be aware of (e.g., Secure access required to certain RCC or watchdog registers?).

• Any best practices on refreshing IWDT from a thread instead of an interrupt or bare-metal loop.

[Saket_Om]

Hello @meghasb 

First you should have the IWDG work without FreeRTOS and then you can add the OS.

please refer to the example below as starting point. 

STM32CubeU5/Projects/NUCLEO-U575ZI-Q/Examples/IWDG/IWDG_Reset at main · STMicroelectronics/STM32CubeU5 · GitHub