wd.h


    #ifndef _AVR_WD_H_
    #define _AVR_WD_H_

    #include <avr/io.h>

    /*
    Copyright (c) 2009, Curt Van Maanen

    Permission to use, copy, modify, and/or distribute this software for any
    purpose with or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.


    include usage-
        #include "wd.h"             //if in same directory as project
        #include <avr/wd.h>         //if wd.h is in avr directory

    set watchdog modes and prescale

    usage-
        WD_SET(mode,[timeout]);     //prescale always set

    modes-
        WD_OFF                      disabled
        WD_RST                      normal reset mode
        WD_IRQ                      interrupt only mode (if supported)
        WD_RST_IRQ                  interrupt+reset mode (if supported)

    timeout-
        WDTO_15MS                   default if no timeout provided
        WDTO_30MS
        WDTO_60MS
        WDTO_120MS
        WDTO_250MS
        WDTO_500MS
        WDTO_1S
        WDTO_2S
        WDTO_4S                     (if supported)
        WDTO_8S                     (if supported)

    examples-
        WD_SET(WD_RST,WDTO_1S);     //reset mode, 1s timeout
        WD_SET(WD_OFF);             //watchdog disabled (if not fused on)
        WD_SET(WD_RST);             //reset mode, 15ms (default timeout)
        WD_SET(WD_IRQ,WDTO_120MS);  //interrupt only mode, 120ms timeout
        WD_SET(WD_RST_IRQ,WDTO_2S); //interrupt+reset mode, 2S timeout


    for enhanced watchdogs, if the watchdog is not being used WDRF should be
    cleared on every power up or reset, along with disabling the watchdog-
        WD_DISABLE();               //clear WDRF, then turn off watchdog

    */

    //reset registers to the same name (MCUCSR)
    #if !defined(MCUCSR)
    #define MCUCSR                  MCUSR
    #endif

    //watchdog registers to the same name (WDTCSR)
    #if !defined(WDTCSR)
    #define WDTCSR                  WDTCR
    #endif

    //if enhanced watchdog, define irq values, create disable macro
    #if defined(WDIF)
    #define WD_IRQ                  0xC0
    #define WD_RST_IRQ              0xC8
    #define WD_DISABLE()            do{                       \
                                        MCUCSR &= ~(1<<WDRF); \
                                        WD_SET(WD_OFF);       \
                                    }while(0)
    #endif

    //all watchdogs
    #define WD_RST                  8
    #define WD_OFF                  0

    //prescale values
    #define WDTO_15MS               0
    #define WDTO_30MS               1
    #define WDTO_60MS               2
    #define WDTO_120MS              3
    #define WDTO_250MS              4
    #define WDTO_500MS              5
    #define WDTO_1S                 6
    #define WDTO_2S                 7

    //prescale values for avrs with WDP3
    #if defined(WDP3)
    #define WDTO_4S                 0x20
    #define WDTO_8S                 0x21
    #endif

    //watchdog reset
    #define WDR()                   __asm__ __volatile__("wdr")

    //avr reset using watchdog
    #define WD_AVR_RESET()          do{                              \
                                        __asm__ __volatile__("cli"); \
                                        WD_SET_UNSAFE(WD_RST);       \
                                        while(1);                    \
                                    }while(0)

    /*set the watchdog-
    1. save SREG
    2. turn off irq's
    3. reset watchdog timer
    4. enable watchdog change
    5. write watchdog value
    6. restore SREG (restoring irq status)
    */
    #define WD_SET(val,...)                                 \
        __asm__ __volatile__(                               \
            "in __tmp_reg__,__SREG__"           "\n\t"      \
            "cli"                               "\n\t"      \
            "wdr"                               "\n\t"      \
            "sts %[wdreg],%[wden]"              "\n\t"      \
            "sts %[wdreg],%[wdval]"             "\n\t"      \
            "out __SREG__,__tmp_reg__"          "\n\t"      \
            :                                               \
            : [wdreg] "M" (&WDTCSR),                        \
              [wden]  "r" ((uint8_t)(0x18)),                \
              [wdval] "r" ((uint8_t)(val|(__VA_ARGS__+0)))  \
            : "r0"                                          \
    )

    /*set the watchdog when I bit in SREG known to be clear-
    1. reset watchdog timer
    2. enable watchdog change
    5. write watchdog value
    */
    #define WD_SET_UNSAFE(val,...)                          \
        __asm__ __volatile__(                               \
            "wdr"                               "\n\t"      \
            "sts %[wdreg],%[wden]"              "\n\t"      \
            "sts %[wdreg],%[wdval]"             "\n\t"      \
            :                                               \
            : [wdreg] "M" (&WDTCSR),                        \
              [wden]  "r" ((uint8_t)(0x18)),                \
              [wdval] "r" ((uint8_t)(val|(__VA_ARGS__+0)))  \
    )


    //for compatibility with avr/wdt.h
    #define wdt_enable(val) WD_SET(WD_RST,val)
    #define wdt_disable()   WD_SET(WD_OFF)


    #endif /* _AVR_WD_H_ */