stm32f103cb_iwdg.c

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/*!***************************************************************************
    @file stm32f103cb_iwdg.c
    @brief Source file for stm32f103cb WATCHDOG 
    @author Stuart Ianna
    @version 0.1
    @date June 2018
    @copyright GNU GPLv3
    @warning None
    @bug 

    @details

    @par Compilers
    - arm-none-eabi-gcc (15:4.9.3+svn231177-1) 4.9.3 20150529 (prerelease)
******************************************************************************/

#include "stm32f103cb_iwdg.h"

mcu_error IWDG_setup(uint32_t timeoutms){

    //Watchdog runs on an independant 40khz oscillator
    //Prescaler rnges from 4-256 in powers of 2
    
    const float watchdog_LSI_period = 1/40.0f; //This is /40 as timeout is in ms
    uint16_t reloadValue;
    uint8_t prescaler; //These are the bits written to the register, not the value itself

    
    //Select the correct prescaler and calculate reload
    if(timeoutms < 400){

        //Prescaler = 4
        prescaler = 0;
        reloadValue = timeoutms/(watchdog_LSI_period * 4) -1; //Subtract 1 as counter counts to 0
    }
    else if(timeoutms < 800){

        //Prescaler = 8
        prescaler = 1;
        reloadValue = timeoutms/(watchdog_LSI_period * 8) -1; //Subtract 1 as counter counts to 0
    }
    else if(timeoutms < 1600){

        //Prescaler = 16 
        prescaler = 2;
        reloadValue = timeoutms/(watchdog_LSI_period * 16) -1; //Subtract 1 as counter counts to 0
    }
    else if(timeoutms < 3200){

        //Prescaler = 32 
        prescaler = 3;
        reloadValue = timeoutms/(watchdog_LSI_period * 32) -1; //Subtract 1 as counter counts to 0
    }
    else if(timeoutms < 6500){

        //Prescaler = 64 
        prescaler = 4;
        reloadValue = timeoutms/(watchdog_LSI_period * 64) -1; //Subtract 1 as counter counts to 0
    }
    else if(timeoutms < 13000){

        //Prescaler = 128 
        prescaler = 5;
        reloadValue = timeoutms/(watchdog_LSI_period * 128) -1; //Subtract 1 as counter counts to 0
    }
    else if(timeoutms < 26000){

        //Prescaler = 256 
        prescaler = 6;
        reloadValue = timeoutms/(watchdog_LSI_period * 256) -1; //Subtract 1 as counter counts to 0
    }
    else{

        //Shouldn't be this long
        if(MCU_debugIsEnabled()){

            MCU_printError(E_IWDG_PERIOD);
        }
        return E_IWDG_PERIOD;
    }


    //Write 0x5555 to enable access to the prescaler and reload registers
    IWDG_KR = 0x5555;

    //Write the preload value
    IWDG_PR = prescaler;

    //Write the reload value
    IWDG_RLR = reloadValue;

    //Write 0xCCCC to the key register to enable the watchdog timer
    IWDG_KR = 0xCCCC;

    return E_IWDG_NOERROR;
}

bool IWDG_resetCheck(void){

    if(RCC_CSR & 0x20000000){

        //Reset the flag
        RCC_CSR |= 0x1000000;
        return true;
    }

    return false;
}

void IWDG_feed(void){

    //Write 0xAAAA to the key register to reload the watchdog timer
    IWDG_KR = 0xAAAA; 
}