Independent Watchdog (IWDG1) implementation. More...

#include "bsp/iwdg.h"
#include "stm32h7xx.h"

Macros
#define	IWDG_KEY_ENABLE 0xCCCCu

#define	IWDG_KEY_REFRESH 0xAAAAu

#define	IWDG_KEY_UNLOCK 0x5555u

Functions
void	IWDG_Init (uint8_t prescaler, uint16_t reload)
	Configure and start the independent watchdog.

void	IWDG_Refresh (void)
	Reload the watchdog counter ("kick" / "feed").

bool	IWDG_WasReset (void)
	Was the most recent reset caused by the IWDG?

void	IWDG_ClearResetFlag (void)
	Clear the IWDG reset flag in RCC->RSR.

Detailed Description

Independent Watchdog (IWDG1) implementation.

Direct CMSIS register access — the HAL IWDG module is left disabled in stm32h7xx_hal_conf.h to avoid pulling in the full HAL_IWDG state machine for what amounts to four register writes.

Register cheat-sheet (RM0433 §50):

IWDG1->KR write key register 0xCCCC = enable 0xAAAA = refresh (reload counter from RLR) 0x5555 = unlock PR/RLR/WINR for write access

IWDG1->PR 3-bit prescaler field [0..6] → div 4..256 IWDG1->RLR 12-bit reload value [1..4095] IWDG1->SR status: PVU (PR write pending), RVU (RLR pending), WVU (WINR pending) — must be 0 before we touch PR/RLR

The reset-reason side reads RCC->RSR (System Reset Status & Control Register on H7) — bit IWDG1RSTF tells us the previous boot was triggered by IWDG1. Cleared via the RMVF bit.

Author: Souham Biswas

Date: 2026

Copyright: Copyright 2025-2026 Souham Biswas https://github.com/ironhide23586/icarus-os-core Licensed under the Apache License, Version 2.0

Definition in file iwdg.c.

Macro Definition Documentation

◆ IWDG_KEY_ENABLE

#define IWDG_KEY_ENABLE 0xCCCCu

Definition at line 40 of file iwdg.c.

◆ IWDG_KEY_REFRESH

#define IWDG_KEY_REFRESH 0xAAAAu

Definition at line 41 of file iwdg.c.

◆ IWDG_KEY_UNLOCK

#define IWDG_KEY_UNLOCK 0x5555u

Definition at line 42 of file iwdg.c.

Function Documentation

◆ IWDG_ClearResetFlag()

void IWDG_ClearResetFlag ( void )

Clear the IWDG reset flag in RCC->RSR.

Note: Safe to call unconditionally; clears the flag even if it was not set. Typically called once at boot after the application has logged the reset reason.

Definition at line 78 of file iwdg.c.

◆ IWDG_Init()

void IWDG_Init	(	uint8_t	prescaler,
		uint16_t	reload
	)

Configure and start the independent watchdog.

Parameters

prescaler	One of the `IWDG_PRESCALER_*` values (3-bit PR field).
reload	12-bit reload value (1..4095). Total timeout is `(reload + 1) × prescaler_div / LSI`.

Note: Once started the IWDG cannot be stopped without a system reset. The function is idempotent — calling it twice with the same arguments is safe.

Definition at line 44 of file iwdg.c.

References IWDG_KEY_ENABLE, IWDG_KEY_REFRESH, IWDG_KEY_UNLOCK, and IWDG_PRESCALER_256.

◆ IWDG_Refresh()

void IWDG_Refresh ( void )

Reload the watchdog counter ("kick" / "feed").

Note: Must be called periodically — at least once per timeout window — or the chip will reset.

Definition at line 70 of file iwdg.c.

References IWDG_KEY_REFRESH.

◆ IWDG_WasReset()

bool IWDG_WasReset ( void )

Was the most recent reset caused by the IWDG?

Returns: true if the IWDGRST flag in RCC->RSR was set on this boot, false otherwise. The flag is sticky until cleared with IWDG_ClearResetFlag(), so this query is safe to call any number of times.

Definition at line 74 of file iwdg.c.

Macros

Functions