void sanity_check()
 {
 // check if battery connected, solar input exists, determine tracking mode, etc.
 // this is called once a second
 //

 // check for non zero current values once a minute, only in NIGHT mode and only once an hour when in night mode
 // if there is, increment cal_sensor_count
 // when it gets to 60, zero it and recalibrate
 //  
 int i;
 if (timeout_check(6,( (track_mode == NIGHT) && ( (fabs(Iin) > 0.1) || (fabs(Iout) > 0.1) )))
   {
     cal_sensor_count ++;
     if (cal_sensor_count > 60)
       {
         cal_sensor_count = 0;
         i = adc_average(IIN,25000);    // get input current sensor offset
         nvd.z_iin = i;                 // save it
         i = adc_average(IOUT,25000);   // etc.
         nvd.z_iout = i;
         nv();                         // write to non volatile ram
       }
   }
..
..

// this will return true once a minute, so with the counter it will run once an hour
 // if night mode, easy, just calibrate
 // if not night mode, stop the converter, wait a bit, then cal. and then re-enable back into absorb mode
 // mppt mode will be enabled automatically if needed
 //
 if ( timeout_check(6,1))
   {
     cal_sensor_count ++;
     if (cal_sensor_count > 60)           // should be 60 for an hour. testing will have it at 2 or something
       {
         cal_sensor_count = 0;           // one hour is up time to recal current sensor zero points
         if (track_mode != NIGHT)
           {
             //stop it
             buck_stop(3);
             track_mode = NIGHT;
             //wait. maybe need this to let caps equalise with battery and solar inputs
             dlay(2000);
             //recal
             i = adc_average(IIN,25000);    // get input current sensor offset
             nvd.z_iin = i;                 // save it
             i = adc_average(IOUT,25000);   // etc.
             nvd.z_iout = i;
             nv();                         // write to non volatile ram
             //restart, set 60 sec timer for mppt close to 60 seconds to more quickly get to mppt scan
             one_min = 55;
           }
         else
           {
             // it's night mode  
             i = adc_average(IIN,25000);    // get input current sensor offset
             nvd.z_iin = i;                 // save it
             i = adc_average(IOUT,25000);   // etc.
             nvd.z_iout = i;
             nv();                         // write to non volatile ram
           }
       }
   }