File content as of revision 5:ea5595e2698b:

/// @file Watchdog.cpp provides the interface to the Watchdog module
///
/// This provides basic Watchdog service for the mbed. You can configure
/// various timeout intervals that meet your system needs. Additionally,
/// it is possible to identify if the Watchdog was the cause of any 
/// system restart.
/// 
/// Adapted from Simon's Watchdog code from http://mbed.org/forum/mbed/topic/508/
///
/// @note Copyright © 2011 by Smartware Computing, all rights reserved.
///     This software may be used to derive new software, as long as
///     this copyright statement remains in the source file.
/// @author David Smart
///
/// @note Copyright © 2015 by NBRemond, all rights reserved.
///     This software may be used to derive new software, as long as
///     this copyright statement remains in the source file.
///
///     Added support for STM32 Nucleo platforms
///
/// @author Bernaérd Remond
///

//#define LPC
#define ST_NUCLEO


#include "mbed.h"
#include "Watchdog.h"


/// Watchdog gets instantiated at the module level
Watchdog::Watchdog() {
#ifdef LPC    
    wdreset = (LPC_WDT->WDMOD >> 2) & 1;    // capture the cause of the previous reset
#endif
#ifdef ST_NUCLEO
    // capture the cause of the previous reset
    /* Check if the system has resumed from IWDG reset */
/*
    if (__HAL_RCC_GET_FLAG(RCC_FLAG_IWDGRST)) {
        wdreset = true;
    }
    else {
        wdreset = false; 
    }
*/        
        wdreset = false; 
#endif

}

/// Load timeout value in watchdog timer and enable
void Watchdog::Configure(float timeout) {
#ifdef LPC    
    LPC_WDT->WDCLKSEL = 0x1;                // Set CLK src to PCLK
    uint32_t clk = SystemCoreClock / 16;    // WD has a fixed /4 prescaler, PCLK default is /4
    LPC_WDT->WDTC = (uint32_t)(timeout * (float)clk);
    LPC_WDT->WDMOD = 0x3;                   // Enabled and Reset
#endif   
#ifdef ST_NUCLEO
    // see http://embedded-lab.com/blog/?p=9662    
    #define LsiFreq (45000)
    
    uint16_t PrescalerCode;
    uint16_t Prescaler;
    uint16_t ReloadValue;
    float Calculated_timeout;
    
    if ((timeout * (LsiFreq/4)) < 0x7FF) {
        PrescalerCode = IWDG_PRESCALER_4;
        Prescaler = 4;
    }
    else if ((timeout * (LsiFreq/8)) < 0xFF0) {
        PrescalerCode = IWDG_PRESCALER_8;
        Prescaler = 8;
    }
    else if ((timeout * (LsiFreq/16)) < 0xFF0) {
        PrescalerCode = IWDG_PRESCALER_16;
        Prescaler = 16;
    }
    else if ((timeout * (LsiFreq/32)) < 0xFF0) {
        PrescalerCode = IWDG_PRESCALER_32;
        Prescaler = 32;
    }
    else if ((timeout * (LsiFreq/64)) < 0xFF0) {
        PrescalerCode = IWDG_PRESCALER_64;
        Prescaler = 64;
    }
    else if ((timeout * (LsiFreq/128)) < 0xFF0) {
        PrescalerCode = IWDG_PRESCALER_128;
        Prescaler = 128;
    }
    else {
        PrescalerCode = IWDG_PRESCALER_256;
        Prescaler = 256;
    }
    
    // specifies the IWDG Reload value. This parameter must be a number between 0 and 0x0FFF.
    ReloadValue = (uint32_t)(timeout * (LsiFreq/Prescaler));
    
    Calculated_timeout = ((float)(Prescaler * ReloadValue)) / LsiFreq;
    printf("WATCHDOG set with prescaler:%d reload value: 0x%X - timeout:%f\n",Prescaler, ReloadValue, Calculated_timeout);
    
    IWDG->KR = 0x5555; //Disable write protection of IWDG registers      
    IWDG->PR = PrescalerCode;      //Set PR value      
    IWDG->RLR = ReloadValue;      //Set RLR value      
    IWDG->KR = 0xAAAA;    //Reload IWDG      
    IWDG->KR = 0xCCCC;    //Start IWDG - See more at: http://embedded-lab.com/blog/?p=9662#sthash.6VNxVSn0.dpuf       
#endif
 
    Service();
}

/// "Service", "kick" or "feed" the dog - reset the watchdog timer
/// by writing this required bit pattern
void Watchdog::Service() {
#ifdef LPC    
    LPC_WDT->WDFEED = 0xAA;
    LPC_WDT->WDFEED = 0x55;
#endif    
#ifdef ST_NUCLEO
    IWDG->KR = 0xAAAA;         //Reload IWDG - See more at: http://embedded-lab.com/blog/?p=9662#sthash.6VNxVSn0.dpuf
#endif
}

/// get the flag to indicate if the watchdog causes the reset
bool Watchdog::WatchdogCausedReset() {
    return wdreset;
}