File content as of revision 9:cd3599adfff6:

//lpc1124lcddemo
// driver for mbed based ppo2 monitoring system for closed circuit rebreather
// reading 3 electrogalvanic oxygen sensors and one pressure sensor
#include "ds1307.h"
#include "mbed.h"
#include "TextOLED.h"

//TODO - MAKE A VERSION THAT DRIVES THE HUD, CHECKS THE 5V SUPPLY AND COMPENSATES THE READINGS IF ITS VARYING (LINEARLY)
// AND PREVENT A HANG IF THE DS1307 FAILS TO RESPOND.

#define DRATIO 0.6420066 // ratio of voltage at pin20 to voltage actually generated by the sensor

//hud LINES
DigitalOut AB(p7); //pins AB for data bits
DigitalOut CP(p5); // clock to shift reg
//DigitalOut MR(p8); // reset to shift reg (low for clear)#
DigitalOut btest(p6); // pin to  drive lastblue led

// offsets for lm324 amp in terms of reading values on adc
#define coff1 -0.013375
#define coff2 -0.00936
#define coff3 -0.0212136



Serial pc(USBTX, USBRX); // tx, rx  for debug and usb pc comunications


//pin assignments and declarations
// LCD display
TextLCD g_lcd(p26, p25, p24, p23, p22, p21);  // RS, E, DB4, DB5, DB6, DB7
//backlight
DigitalOut backlight(p29);

//onboard leds
DigitalOut led1(LED1);
DigitalOut led2(LED2);

// warning leds
DigitalOut red(p34);
DigitalOut green(p33);
DigitalOut blue(p30);


// switches and buttons - these are pulled up by resistors so are active low
DigitalIn CAL(p36);
DigitalIn SW1(p35); // reed switch in display unit
DigitalIn SW2(p10); // reed switch in dispaly unit - NONE FUNCIONAL IN CURRENT HEAD - SWITCH FAILED DURING POTTING
//DigitalIn MODE(p11);// a switchn on the mbed pcb to select between SCR and CCR modes for the LEDs NOT USED ANYMORE

// log data storage
LocalFileSystem local("local");

// adc inputs for sensors
AnalogIn PRESin(p20);
AnalogIn EG1(p19);
AnalogIn EG2(p18);
AnalogIn EG3(p16); 
AnalogIn Vbatt(p17); // battery voltage divided down by 3
AnalogIn V5V(p15); // sense the '5V' output from the max1724 unit - divided down by 2.  Nominally 2.5V===0.757575757' in 3.3V ADC



// realtime clock
DS1307 my1307(p28,p27); // start DS1307 class and give it pins for connections of the DS1307 device

// variables for realtime clock
int sec = 0;
int min = 0;
int hours = 0;
int day = 0;
int date = 0;
int month = 0;
int year = 0;
int seconds=0; // general number of seconds since 2000 etc timestamp variable

int scrubtime=0,scrubold=0; // these are expressed in minutes
int divetime=0;

int flash=0; // variable used top control flashing icons
int state=0; // IMPORTANT - VARIABLE THAT DRIVES HNTE STATE MACHINE STATE=0 = STARTUP, STATE=1=SURFACE  STATE=2= DIVING
float lowsetpoint=0.7,highsetpoint=1.2,switchdepth=10; // variables to determine HUD led states 
//switchdepth is centre of switch region 1m deep if switchdepth=10 then will go to high as descebnd 
//through 10.5 and go back to low when ascending through 9.5
int setpoint=0; // 0=low 1 = high

// variables for the eg cells and pressure sensor eg1calamd eg2cal ar reading when the sensor is in 0.21bar O2 and
//dcal is the reading whe the pressure sensor is at the surface
float eg1cal=0.09,eg2cal=0.09,eg3cal=0.09,pcal=0.1136;
// NB these are updated from /local/cal.dat so values not so important.... eventually

float depth=0,ppo1=0,ppo2=0,ppo3=0  ,Vb=0,pressure=0; // depth, 1st o2 sensor second o2 sensor battery voltage,,Pressure
float fo1=0,fo2=0,fo3=0,mod=55; //%f values,mod

FILE *lp; // file pointer for log file

bool nostop=1, deco=0; // variables to define state for deco



//HUD codes
// make a HUD clock pulse
int clk()
{
    wait_us(1);
    CP=0;
    wait_us(1);
    CP=1;
    return(0);
}

// write 8 bits to the HUD shift register
int HUD_write(char d)
{
    int i=0;
    for(i=7; i>=0; i--) {
        AB=d & (1 << i);
        AB=!AB;
        clk();
    }
    return(0);
}

// make all HUD leds white - useful for warnings etc
int HUD_white()
{
    // set all white;
    HUD_write(255);
    btest=0;

    return(0);
}
// clear the HUD - make al black
int HUD_clr()
{
    HUD_write(0);
    btest=1;
    return(0);
}



// code to detect leap years
int LeapYear(int year) {
    int leap=0;

    if (year % 400==0) leap=1;
    else if (year %100 ==0) leap=0;
    else if (year % 4 ==0) leap=1;
    else leap=0;
    return(leap);
}


//===== sub to get time from ds1307 and create the 'seconds' which is a version of timestamp....
int getseconds() {
    int leap=0,dayofyear=0,timestamp=0;
    int y=0,byear=0;
    int days[12]={0,31,59,90,120,151,181,212,243,273,304,334};
    my1307.gettime( &sec, &min, &hours, &day, &date, &month, &year);
    //simple timestamp = # seconds since midnight jan 1st 2000 if all months were 30 days.
    //int secondst=year*365*24*60*60+month*30*24*60*60+day*24*60*60+hours*60*60+min*60+sec;
    //simple timestamp = # seconds since midnight jan 1st 2000 if all months were 30 days....
    // ie wrong but simpler than the real thing


    // sort out ds1307 definiteion of year
    year=year+2000;
    leap=LeapYear(year);

    // now decide dayofyear
    dayofyear=days[month-1]+date-1;
    if (leap==1 && month >2) dayofyear++; // deal with extra february day in leap year

    // now find number of days since 1970
    for (y=1970; y<year; y++) {
        if (LeapYear(y) == 1) {
            byear += 366*24*60*60;
        } else {
            byear += 365*24*60*60;
        }
    }

    // finally get the seconds right and construct timestamp in seconds since beginning of 1970
    timestamp=(byear)+dayofyear*24*3600+hours*3600+min*60+sec;

    //DEBUG====================================
    // printf("secondst =  %d\t timestamp = %d\t%.2d : %.2d : %d - %.2d:%.2d:%.2d\r",secondst,timestamp,date,month,year,hours,min,sec);

    return(timestamp);

}


void set_custom_char() {
    char cgchar[64]={
        6,9,9,9,9,9,9,15, // battery  symbol                    0 address 64 = 0x40
        28,20,20,20,20,20,29,0, //  0. symbol for ppo2          1 address 72 = 0x48
        8,24,8,8,8,8,29,0, // 1. symbol for ppo2                2 address 80 =0x50
        6,15,15,15,15,15,15,15, // unused                       3 address 88 = 0x58
        31,19,21,21,21,21,19,31,  // unused                     4 address 96 = 0x60
        6,6,6,6,6,0,0,6,             // top char Vmessg         5 address 104 =0x68 - used for Vmessage
        31,17,23,17,29,17,31,0, // bottom char Vmessg           6 address 112 =0x70 -used for Vmessg
        2,6,2,2,2,2,23 // for dec point in depth                7 address 120 =0x78
    };
    int i=0;
// do stuff here to set cstom chars
    g_lcd.writeCommand(0x40); // set start address for CGRAM
    for (i=0; i<64; i++) {
        g_lcd.writeData(cgchar[i]);
    }

}

// stash cal values on local drive
void store() {
    int timestamp=0;
    timestamp=getseconds();
    wait(0.1);
    FILE *fp=fopen("/local/CAL.dat","w");
    fprintf(fp,"%e\n%e\n%e\n%e\n%d\n%d\n",eg1cal,eg2cal,eg3cal,pcal,scrubtime,timestamp);

    fclose(fp); //NB file system locked on write so must make sure we close files in case want to reprogram etc...
    wait(0.1);
}


// subroutine to calibreate o2 sesnors and store ca data in /local/CAL.dat
void calibrate() {
    int count=1;
    float s1=0,s2=0,s3=0,pres=0;
    // average 20 readings for noise reduction
    g_lcd.cls();
    for (count=20; count>0; count--) {
        s1=s1+EG1;
        s2=s2+EG2;
        s3=s3+EG3;
        pres=pres+PRESin;
        g_lcd.locate(0,0);
        g_lcd.printf("CAL 21%% %.2d %1.2f",count,pres/(20-count+1));
       
        g_lcd.locate(0,1);
        g_lcd.printf("%1.2f: %1.2f: %1.2f",s1/(20-count+1),s2/(20-count+1),s3/(20-count+1));
        wait(1);
    }
    //average
    s1=s1/20-coff1;
    s2=s2/20-coff2;
    s3=s3/20-coff3;
    // set calibration variables
    eg1cal=s1;
    eg2cal=s2;
    eg3cal=s3;
    pcal=pres/20/DRATIO; // surface pressure output voltage from sensor
    scrubtime=0; // reset the scrubber timer to zero.
    scrubold=0; // set stored scrub time to zero too.
    // write cal data NB overwites previous
    /*  FILE *fp=fopen("/local/CAL.dat","w");
      fprintf(fp,"%e\n%e\n%e\n%d",eg1cal,eg2cal,pcal,scrubtime);
      fclose(fp); //NB file system locked on write so must make sure we close files in case want to reprogram etc...*/
    store();
}

// sub to test if a variable is an even number
int iseven(int g) {
    int test=0;
    if (g%2 ==0) test=1;
    return(test);
}


void status() {
   /* if (state==0) {
        g_lcd.character(7,0,33); // warning icon until 1 min up
        g_lcd.character(8,0,83); // surface icon - letter S
    } else {
        g_lcd.character(7,0,32);
    }
    if (state==1) g_lcd.character(8,0,83); // surface icon
    if (state==2 && iseven(seconds)==1) g_lcd.character(8,0,4); // diving icon - inverse D
    if (state==2 && iseven(seconds)==0) g_lcd.character(8,0,68); // diving icon - normal D
    */
// yes - this does nothing as all this is now done by vmessage
}

// warning and LED conditions

void warning() {
    if (depth>=mod && flash==1) g_lcd.character(11,0,33);
    else g_lcd.character(11,0,32); // blank sapce

}

// pick maximum of two values
float maximum(float a,float b,float c) {
    float maximum;
    if(a>b && a>c) maximum=a;
    if(b>a && b>c) maximum=b;
    if(c>a && c>b) maximum=c;
    return(maximum);
}

// pick minimum  of three values
float minimum(float a,float b,float c) {
    float minim;
    if (a<b && a < c) minim=a;
    if(b<a && b<c) minim=b;
    if(c<a && c <b) minim=c;

    return(minim);
}


// handset led control
void leds() {
// first turn everything off
    red=0;
    green=0;
    blue=0;
    float ppox,ppom,sp;
    int mo=0;
    //mo=MODE;
    if(setpoint==0) sp=lowsetpoint;
    else sp=highsetpoint;
    ppox=maximum(ppo1,ppo2,ppo3); // use max value to compute leds...
    ppom=minimum(ppo1,ppo2,ppo3); // unless we want minimum
    if (mo==0) { // CCR mode
        if (ppom<0.2 && flash==1) {red=1;} // flashing red means very bad things - getting very --low on oxygen!!!
        if (ppom>0.2 && ppox < (sp-0.15)) red=1; // non-flashing red
        if (ppox>=(sp-0.15) && ppox <(sp-0.5)) {
            red=1;    // red-green
            green=1;
        }
        if (ppox<(sp+0.05) && ppox >=(sp-0.05)) green=1; // green - optimal range in ccr mode
        if (ppox<(sp+0.15) && ppox >=(sp+0.05)) {
            green=1;    // green-blue - high ppo2 be careful of spiking
            blue=1;
        }
        if (ppox<1.6 && ppox>=(sp+0.15)) blue=1; // DANGER blue high ppo2
        if (ppox>=1.6 && flash==1) blue=1;
    }
   /*if (mo==1) { // SCR mode
        if (ppom<0.2 && flash==1) red=1;
        if (ppom>=0.2 && ppox <0.26) red=1; // will give green red for low but not lethal ppo2s
        if (depth < 0.8*mod && ppom>0.2) green=1;
        if (depth< mod && depth >=0.8*mod) {
            green=1;
            blue=1;
        }
        if (depth >=mod && flash==1) blue=1;
    }*/

}



//read battery state and insert the battery symbol
void battery() {
 char cgchar[32]={
        6,9,9,9,9,9,9,15, // battery empty symbol         
        6,9,9,9,9,15,15,15, // battery 50% symbol         
        6,9,9,15,15,15,15,15, // battery 75% symbol       
        6,15,15,15,15,15,15,15, // battery 100% symbol    
        };


    int batsym=0,i=0; // battery < 3.85V


    // idea to build in 6 levels of battery indicator by on the fly reprogramming character 2 as required.
    Vb=0;
    for (i=0; i<4; i++) {
        Vb=Vb+Vbatt; // read adc connected to battery via a 1/3 potential divider
        wait(0.05);
    }
    Vb=Vb/4; // average 4 readings to reduce noise

    if (Vb>0.388) batsym=8; //3.85-3.92V
    if (Vb>0.395) batsym=16; // battery 3.92-4V
    if (Vb>0.404) batsym=24; // battery . >4V


// write the appropriate battery symbol into the first custom character
    g_lcd.writeCommand(0x40); // set start address for CGRAM
    for (i=0; i<8; i++) {
        g_lcd.writeData(cgchar[i+batsym]);
    }

g_lcd.character(11,1,0); // battery symbol
 if (batsym ==0 && flash==0) g_lcd.character(11,1,32); // bung in space if flashing


}

// sub to make the nice stop or no stop message work in locations 9,0 and 9,1
void vmessage() {
int i,d,cpos=0;
// "INITSURFDIVE" in vertical chas - 1 custom char per two symbols
   char mesg[48]={  17,31,17,0,31,6,12,31, 0,17,31,17,0,1,31,1,  19,21,25,0,31,16,31,0,    31,13,23,0,31,5,1,0,   31,17,14,0,17,31,17,0,  15,16,15,0,31,21,17,0};
                  
   
 
   g_lcd.writeCommand(104); // set start address for CGRAM characrter #6 out of 8

    for (i=0; i<16; i++) { // write 2 chars worth into this segment NO DECO
   

       g_lcd.writeData(mesg[i+state*16]);
    } // endfor


    
g_lcd.character(12,0,5); // custom char 5

g_lcd.character(12,1,6); // custom char 6

}


// subroutine to write the main display data
//0123456789abcdef

//x.xx:xx D XX  xx
//x.xx:xx B XX xxx NB the warning, staus and battery icons are driven by separate subroutines.
void display() {
    int mo=0,tmp=0;
    //mo=MODE;
    g_lcd.character(3,1,32);
//1st line

 //ppo1
    if(ppo1<1) tmp=(int)(ppo1*100); else tmp=(int)(ppo1*100-100);
    g_lcd.locate(1,0);
    g_lcd.printf("%02d ",tmp);
    if(ppo1>=1) g_lcd.character(0,0,2);
    if(ppo1<1) g_lcd.character(0,0,1);
    
    if(ppo2<1) tmp=(int)(ppo2*100); else tmp=(int)(ppo2*100-100);
    g_lcd.locate(5,0);
    g_lcd.printf("%02d ",tmp);
    if(ppo2>=1) g_lcd.character(4,0,2);
    if(ppo2<1) g_lcd.character(4,0,1);
    
    if(ppo3<1) tmp=(int)(ppo3*100); else tmp=(int)(ppo3*100-100);
    g_lcd.locate(9,0);
    g_lcd.printf("%02d ",tmp);
    if(ppo3>=1) g_lcd.character(8,0,2);
    if(ppo3<1) g_lcd.character(8,0,1);
    
    g_lcd.locate(13,0);
    g_lcd.printf("%.2d",(int)depth); // depth
    g_lcd.locate(4,1);
    g_lcd.printf("%2dm",(int)mod); // mod
//2nd line
    g_lcd.locate(0,1);
    tmp=minimum((float)fo1,(float)fo2,(float)fo3); // get min fraction of oxygen to display lowest for deco use
    g_lcd.printf("%2d%%",tmp);
    g_lcd.locate(13,1);
    g_lcd.printf("%03d",scrubtime % 1000); // modulo to avoid digits conflict - means divetime is always less than 100
    g_lcd.locate(8,1);
    g_lcd.printf("%2d",(int)(divetime/60) % 100 ); // rolls back to zero if go over 99
    // bung in battery icon
    battery();
    status(); // this will set the diving / suface mode icon
 //   warning(); // this will set the warning ic on assuming that max ppo2 is exceeded
    g_lcd.character(7,1,32); // space to cover any write error on top line
    leds(); // this sets the leds according to the various warning conditions
   /* if (mo==0) {
        g_lcd.character(7,1,99);    //'c' = ccr
    } else {
        g_lcd.character(7,1,115);    //'s' = scr
    }*/
    // custom character setting to sort out dp in depths


    char cgchar[80]={
        7,5,5,5,23,0,0,0, // .0
        2,2,2,2,18,0,0,0, //  .1
        7,1,7,4,23,0,0,0, // .2
        7,1,3,1,23,0,0,0, // .3
        5,5,7,1,17,0,0,0, //.4
        7,4,7,1,23,0,0,0, //.5
        7,4,7,5,23,0,0,0, //.6
        7,1,2,2,18,0,0,0, //.7
        7,5,7,5,23,0,0,0, //.8
        7,5,7,1,17,0,0,0 //.9

    };
// special dp digit for depth
    int i=0,d=0;
    d=(int)((depth-(int)depth)*10); // should be size of the 1st decimal place
// do stuff here to set cstom chars
    g_lcd.writeCommand(120); // set start address for CGRAM
    for (i=0; i<8; i++) {
        g_lcd.writeData(cgchar[i+d*8]);
    }

    g_lcd.character(15,0,7); // put in appropriate custom character
    
    // display the current setpoint information
    if(setpoint==0)    g_lcd.character(7,1,218); // letter down arrow for low setpoint
    if(setpoint==1)    g_lcd.character(7,1,217); // Letter 'H'
    if(flash==1)  g_lcd.character(7,1,115); // Letter ':'

}




// read sensors and generate calibrated outputs NB battery is read elsewhere

void readsensors() {
    float barometric=0,mod1,mod2,mod3,temp,Vdepth=0,s1,s2,s3,MPXref=0;
    int tc=0;
  //  ppo1=EG1*0.21/eg1cal; // eg1cal is 0.21bar ppO2
  //  ppo2=EG2*0.21/eg2cal; // second oxygen cell ppO2
  //  ppo3=EG3*0.21/eg3cal;
   
    s1=0;
    s2=0;
    s3=0;
    for(tc=0;tc<20;tc++) // noise on Vdepth so average readings to compensate
    { 
    Vdepth=Vdepth+(PRESin/DRATIO); // read the depth sensor and calculate the real value rather using the dividing ratio
    wait_ms(10); // slows stuff down a bit but not a big problem
    s1=s1+EG1; // read o2 sensors
    s2=s2+EG2;
    s3=s3+EG3;
    MPXref=MPXref+V5V; // read 5V
    wait_ms(10); // slows stuff down a bit but not a big problem
    }
    Vdepth=Vdepth/20; // now have the average
    s1=s1/20-coff1;
    s2=s2/20-coff2;
    s3=s3/20-coff3;
    MPXref=MPXref/20*3.3*2; // should be 5V

    
    // compute ppO2s
    ppo1=s1*0.21/eg1cal;
    ppo2=s2*0.21/eg2cal;
    ppo3=s3*0.21/eg3cal;
    
    pc.printf("EG1=%f\tEG2=%f\tEG3=%f   \tMPXref=%f                             \r",s1,s2,s3,MPXref);
    pressure=(Vdepth*3.3/MPXref-0.04)/0.0012858; // pressure in kpa NB - assums that the 5V is correct
    //pressure=(PRESin*3.3/0.65006-0.04)/(0.0012858); // pressure in kPa assuming standard cal for mpx5700 sensor SUSPECT
    // NB the mpx5700 runs off 5v so would be better to divide its output down by 3/5 to get full range measurement
    //outputs. with no division the max mbed adc of 3.3V coresponds to 480kpa or about 38m depth.....
    // standard spec on mpx5700 should be 5V*(P*0.0012858+0.04)
    // new sensor has 3/5 divider built into sensor wiring.
    //barometric=(pcal*3.3/0.65006-0.004)/(0.0012858); // sealevel in kPa assuming standard cal for mpx5700 sensor
    barometric=(pcal*3.3/MPXref-0.04)/0.0012858; // barometric pressure (kpa) evaluated from calibration which we assume is baseline
    depth=(pressure-barometric)*0.1;   //100kPa=10m 1kPa=0.1m - this gives depth in m for freshwater.
    
    if (depth<0) depth=0; // deals wtih noise that may lead to small variation in values

// THESE SHOULD BE JUST 100*ppox/(pressure/100);
    fo1=100*ppo1/((pressure-barometric)/100+1); // pressure in bar = pressure /100 and want a % so multiply by 100 as well
    fo2=100*ppo2/((pressure-barometric)/100+1);
    fo3=100*ppo3/((pressure-barometric)/100+1); // maybe these should be ppox/(depth/10+1)*100....?

    /*if (fo1<0) fo2=0;
    if (fo2<0) fo1=0;
*/
    //with three sensors will calculate mod from the largest ppo2 reading
    mod1=(1.4/(fo1/100)-1)*10;
    mod2=(1.4/(fo2/100)-1)*10;
    mod3=(1.4/(fo3/100)-1)*10;

    mod=minimum(mod1,mod2,mod3); // pick the least value
    
   // output for debugging to pc via usb line.
  //  pc.printf("VDepth %f\tPressure %f\tbarometric %f\tdepth %f\t  \n\r",Vdepth,pressure,barometric,depth);
    //NB - problem - we really need to monitor the 5V power line to ensure that it's driving the depth sensor ok.
    // it may need thicker cables as it currently only manages 4.8V on the board when everything is running.

}
// get values back from cal file on local drive
void recall() {
    FILE *fp=fopen("/local/CAL.dat","r");
    fscanf(fp,"%e\n%e\n%e\n%e\n%d",&eg1cal,&eg2cal,&eg3cal,&pcal,&scrubold);
    fclose(fp); //NB file system locked on write so must make sure we close files in case want to reprogram etc...
}

// write the logfile opened and closed by start and end of dive
void store_log() {

    //FILE *fp=fopen("/local/divelog.dat","a");
    float v5=0;
    v5=V5V;
    fprintf(lp,"%d\t%e\t%e\t%e\t%e\t%e\t%e\t%d\n",seconds,depth,ppo1,ppo2,ppo3,Vb,v5,scrubtime);

    if (divetime % 60==0) fflush(lp);
    // fclose(fp);
}

// read switches and report state
int switches() {
    int ss=0;
    if (SW1==1 && SW2==1) ss=3;
    if (SW2==1 && SW1==0) ss=2;
    if (SW1==1 && SW2==0) ss=1;
    return(ss);
}

// interpret the ppo2 data into a simple set of hud codes.
int HUD_display()
{ 
    int i,j3,h1,h2,h3;
    float cset=0;
      char gcode[6]={0,1,3,2,6,4}; // grey code for HUD reading 'red,amber,green,cyan,blue'
    
    HUD_clr(); // clear the HUID ready for write
   
    
    if(setpoint==0)  // low setpoint
    {
    cset=lowsetpoint;
    }
    
    if(setpoint==1) // hgh setpoint
    {
    cset=highsetpoint;
    }

    h1=(int)((ppo1-cset)/0.1+3.5);
    if(h1<1) h1=1;
    if(h1>5) h1=5;
    h2=(int)((ppo2-cset)/0.1+3.5);
    if(h2<1) h2=1;
    if(h2>5) h2=5;
    h3=(int)((ppo3-cset)/0.1+3.5);
    if(h3<1) h3=1;
    if(h3>5) h3=5;
    
    if(h3>3) btest=0; // handle extra blue connected to btest setting btest low lights blue led
    
    
    i=gcode[h1]+8*gcode[h2]+64*gcode[h3]; // this is possible bigger than a char so have to typeconvert
    HUD_write(i);
       
}

// sub to flash HUD n times as a warning of setpoint shift
int HUD_flash(int n)
{
    int i;
    for(i=0;i<n;i++)
    {
    HUD_clr();
    wait(0.2);
    HUD_white();
    wait(0.05);
    }
}

int setswitch()
{
    if(setpoint==0 && depth >(switchdepth+0.5)) 
    { 
        setpoint=1; // handle switch from low to high
        HUD_flash(4);
        // flash the hud here
    }
    
    if(setpoint==1 && depth < (switchdepth -0.5))
    {
        setpoint=0;  // swtich to low setpoint
        HUD_flash(2);
        // flash the HUD here
    }
}

int main() {
// first some local variables
    int startuptime=getseconds();
    int startdive=0,endclock=0; // value of seconds when dive starts and counter to decide if dive complete...

    int minutes=0; // minutes is elapsed minutes since start of prog
    int j=0,scount=1;; // general loop counting variable
    int sw=0; // status of the switches in the handset
    char schars[4]={32,0xd9,0xda,0xfb}; // up arrow, down arrow and both arrows;

    bool mdir=0;

    set_custom_char(); // does what it says on the tin really
    g_lcd.cls();
    g_lcd.locate(0, 0);
    g_lcd.printf( "RebMon");
    g_lcd.locate(0,1);
    g_lcd.printf("CAL?");
    battery();
    j=0;
wait(0.2);

    // get cal values last used from local drive
    recall();
    // display the correct scrubber time
    scrubtime=scrubold;
// hang about waiting for the cal switch to be pressed in ccase it is
    while (scount<30) {
        seconds=getseconds(); // NB if this hangs then nothing works :( - usually means 5V is dodgy
        red=1;
        green=1;
        blue=1; // light all leds

        g_lcd.locate(5,1);
        g_lcd.printf("%.2d ",30-scount);
        if (j>1) flash=1;
        else flash=0;
        battery(); // bung in battery symbol.
        g_lcd.locate(7,0);
        g_lcd.printf( "%.2d:%.2d:%.2d", hours,min,sec);
      //  if (CAL==0) {
        if(SW1==0) {
            calibrate();
            scount=31; // make sure it goes to next frame ok
        }
        wait(0.05);


        j=(j+1) % 4;
        if(flash==0) HUD_white();
        else HUD_clr();
        scount++;
    } 
    g_lcd.cls();


    // ok there are three states in this system
//MAIN LOOP ONCE STARTUP PROTOCOLS ARE COMPLETED
    j=0;
    g_lcd.cls();
    while (1) {
        wait(0.1); //stop screen flicker
        readsensors();
        setswitch(); // check the setpoint and adjust if crossing the swtich depth
        HUD_display(); // write the HUD codes
        seconds=getseconds();
        minutes=(int)(((float)seconds-(float)startuptime)/60);
        led1=seconds % 2; // flash the onboard led to make it clear stuff is running

        if (j>1) flash=1;
        else flash=0;

        display(); // write the display
        HUD_display(); // write the HUD
      // sw=switches(); // read the switches and report their state
      // if(SW1==0) g_lcd.character(11,0,0xEF); else g_lcd.character(11,0,32); // NB here is possible alternate display underwater switching point
        // HERE do deco calcs - update tissues and compute desat , nostop or ascent times as required.

        // setup state variable
      if (minutes<1) state=0; // startup mode - do nothing just wait to allow sensor readings to settle.
        if (minutes>=1 && state==0) state=1; // surface mode - ok to go for a dive now
        if (minutes>=1 && depth>0.8 && state==1) {
            state=2; // enter dive mode
            lp=fopen("/local/divelog.dat","a");
            fprintf(lp,"#startdive = %d\n#seconds\tdepth\tppo1\tppo2\tppo3\tVb\t\tV5V\tscrubtime\n",seconds); // bung in a header here in case one needs it
            store_log(); // make a first log entry to catch this erliest part of the dive
            if (startdive==0) startdive=seconds; // set start of divetime. don't do this twice
            endclock=0; // reset end of dive clock
        }
        // in dive mode - things to do, 1 update divetime and scrubber time, 2 write log data 3 check for end of dive...
       if (state==2) {
            // divetime=(int)(((float)seconds-(float)startdive)/60.0); // time since start of dive in minutes.
            divetime=(seconds-startdive); // divetime no recorded in seconds since start of dive

            // do deco calcs here when implemented
            if (divetime %15 ==0) store_log(); // this saves the dive profile data every 15s and sensor optputs in a file called divelog.dat
            if (depth<=0.5) {
                endclock=endclock+1;

                if (endclock>150) {
                    state=1; // 30s at shallower than 0.5m and we return to surface mode. */
                    FILE *fp=fopen("/local/CAL.dat","w");
                    fprintf(fp,"%e\n%e\n%e\n%d",eg1cal,eg2cal,pcal,scrubtime);
                    fclose(fp); //NB file system locked on write so must make sure we close files in case want to reprogram etc...
                    
                    store();
                    fclose(lp);
                } // endif endclock
                   
            } // end if depth
            scrubtime=scrubold+(divetime/60); //
        } // end state 2


        j=(j+1) %4; // flash control variable = used to make the warnings flash for 0.4s duty cycle


        vmessage(); // call to generate status message in vertical segment
    } // end while
} //end main