File content as of revision 0:61364762ee0e:

#ifndef FAILSAFECONTROL_H
#define FAILSAFECONTROL_H

#include <stdio.h>
#include <string>
#include "global.h"

#define FAILSAFE_CONTROL_DEBUG

typedef enum {
    FAILSAFE_CONTROL_OK,
    FAILSAFE_CONTROL_UNK_STATE,
    FAILSAFE_CONTROL_ERROR,
} FailsafeControlError_t;

//! FailsafeControl - implements a failsafe by reading values from an
// input signal and manipulating an output.
class FailsafeControl
{
private:
    std::string     controlFile;            // the control file
    std::string     id;                     // unique control identifier
    std::string     input;                  // sensor to read
    std::string     output;                 // output to manipulate
    unsigned int    priority;               // control priority (typically 700)

    typedef struct  hfs_tag {
        float       value;                  // high-failsafe trigger value
        float       dutyCycle;              // percentage of on-time
        float       interval;               // in minutes
    } hfs;
    typedef struct lfs_tag {
        float       value;                  // low-failsafe trigger value
        float       dutyCycle;              // percentag of on-time
        float       interval;               // in minutes
    } lfs;

    lfs             lfs_data;               // Low Failsafe data
    hfs             hfs_data;               // High Failsafe data

    typedef struct timer_tag {
        unsigned long   offTime;            // epoch time
        unsigned long   expirationTime;     // epoch time
    } Timer_t;

    Timer_t         duty_timer;             // the duty timer

    enum State {
        STATE_INIT,                         // object instantiated
        STATE_START,                        // control has been started
        STATE_CONTROL_OFF,                  // control is not above/below limit
        STATE_CONTROL_ON_LFS,               // low-failsafe with output on
        STATE_CONTROL_OFF_LFS,              // low-failsafe with output off
        STATE_CONTROL_ON_HFS,               // high-failsafe with output on
        STATE_CONTROL_OFF_HFS,              // high-failsafe with output off
        STATE_CONTROL_SENSOR_ERROR,         // input sensor is faulted
        STATE_MAX
    };
    State           currentState;
    
    bool            isVirtualOutput;

    bool validateControlData(const char *buf);
    void copyControlData(const char *buf);
    
    bool aboveHighFailsafe(void);           // boolean check if above HFS watermark
    bool belowLowFailsafe(void);            // boolean check if below LFS watermark

    void startHfsDutyTimer(void);           // start the HFS duty timer
    void stopHfsDutyTimer(void);            // stop the HFS duty timer

    void startLfsDutyTimer(void);           // start the LFS duty timer
    void stopLfsDutyTimer(void);            // stop the LFS duty timer

    bool dutyOnExpired(void);               // boolean check if duty ON-time expired
    bool dutyOffExpired(void);              // boolean check if duty OFF-time expired

    bool sensorError(void);                 // boolean check if input is faulted

    void sendMailToOutput(OutputAction action);

public:
    /// Create a failsafe control instance
    FailsafeControl() {
        currentState = STATE_INIT;
        isVirtualOutput = false; 
    }
    /// Destroy a failsafe control instance
    ~FailsafeControl() {
        // "erased...from existence!" -- Doc Brown
        printf("\r%s invoked\n", __func__);
    }

    /// load a failsafe control instance with data from a JSON configuration file
    bool load(std::string filename);

    /// start a failsafe control instance
    void start(void);

    /// update a failsafe control instance
    FailsafeControlError_t update(void);

    /// unregister a failsafe control instance
    void unregisterControl(void);


    /// display  the pertinent data of a failsafe control instance
    void display(void);

    /// get control identifier 
    std::string getId() const {
        return id;
    }
};

#endif