RTC auto calibration

Hydra_EVSE/Hydra_EVSE.h

@@ -479,6 +479,10 @@ typedef struct calib_struct {
 // eprom persistence format signature (usually minimally compatible SW_VERSION):
 // 2.4.1
 #define PERSIST_SIG 241
+
+// debug to reset eprom
+//#define PERSIST_SIG -1
+
 #define EEPROM_OFFSET 0
 
 struct persisted_struct {
@@ -491,7 +495,9 @@ struct persisted_struct {
   event_struct events[EVENT_COUNT];
   calib_struct calib;
 
-  persisted_struct() {
+  RTCModel rtc;
+
+  persisted_struct() : rtc(0.5) {
     eepromRead();
     validate();
   }

Hydra_EVSE/Hydra_EVSE.ino

@@ -1171,9 +1171,13 @@ void doClockMenu(boolean initialize)
       // The underlying system clock is always winter time.
       // Note that setting the time during the repeated hour in
       // the fall will assume winter time - the hour will NOT repeat.
-//      if (enable_dst) toSet = dst.toUTC(toSet);
+
+      time_t oldTime = now;
       setTime(toSet);
       RTC.set(toSet);
+      RTC.setCalibration(persisted.rtc.update(toSet, toSet-oldTime));
+      persisted.eepromWrite();
+
       doMenuFunc = doMenu;
       inMenu = false; // exit all menus
       display.clear();

Hydra_EVSE/onlineSum.h

@@ -21,9 +21,11 @@
 #ifndef ___ONLINESUM_H___
 #define ___ONLINESUM_H___
 
+#include "Arduino.h"
+
 ///////////////////////////////////////////////////////////////////
 // Exponentially Weighted Average summarizer for irregularly sampled data.
-// References: 
+// References:
 // http://tdunning.blogspot.com/2011/03/exponentially-weighted-averaging-for.html
 // My mods for the updates-in-the past (ensures no NaNs created regardless of updates order):
 // http://weatheringthrutechdays.blogspot.com/2011/04/follow-up-for-mean-summarizer-post.html
@@ -32,15 +34,17 @@
 template <class T>
 class EWASum {
 
+  friend class RTCModel;
+
     T alpha;
     T w, s, tn;
 
   public:
-  
-    // tHalfWeightPeriod is the amount of t (timeline point) in the past at which the observation is 
-    // exponentially weighed at exactly 0.5 vs. any observation right now. Since it is weighed 
-    // exponentially rather than linearly, observations at full period still do have a nonzero weight, 
-    // and in general with this summarizer most recent observations are being discounted at fastest 
+
+    // tHalfWeightPeriod is the amount of t (timeline point) in the past at which the observation is
+    // exponentially weighed at exactly 0.5 vs. any observation right now. Since it is weighed
+    // exponentially rather than linearly, observations at full period still do have a nonzero weight,
+    // and in general with this summarizer most recent observations are being discounted at fastest
     // weight but never actually discounted completely (indefinite history), down to the precision of
     // the arithmetics. At full period the weights are thus still coming in at exp(-2) = 0.135 (13.5%).
     EWASum(T tHalfWeightPeriod) : alpha(-tHalfWeightPeriod / log((T)0.5)) {
@@ -72,14 +76,50 @@ void EWASum<T>::update(T x, T t) {
 
 template <class T>
 T EWASum<T>::ewa() {
-  // In this sum, weights low enough should not happen, as we never discount the most recent weight, 
-  // which is at least one. So w>= 1 if there were at least one sample; and w = exactly 0 if there 
-  // are no samples at all. With no samples, we just return 0. 
+  // In this sum, weights low enough should not happen, as we never discount the most recent weight,
+  // which is at least one. So w>= 1 if there were at least one sample; and w = exactly 0 if there
+  // are no samples at all. With no samples, we just return 0.
   return (abs(w) < 1e-6) ? 0 : s / w;
 }
 
 // On Arduino, double seems to be the same as float and take 4 bytes!
 typedef EWASum<double> EWASumD;
 typedef EWASum<float> EWASumF;
 
+#define RTC_CALIB_PERIOD SECS_PER_DAY
+
+// RTC model
+class RTCModel {
+
+  protected:
+
+    EWASumD   ewa;
+    char      calib, calibErr;
+    double    initCalibRate, rate, dn;
+
+  public:
+
+    // for PT7C4311WEX, actual rate to add seconds per day seems to be 0.35, and to delete seconds is 0.175.
+    // in simulations, 0.5 seems to be a good initial value.
+    // half rate period should be in seconds, e.g., 2* SECS_PER_WEEK seems to be a good value.
+    RTCModel(double initCalibRate);
+
+    // update model after time adjustment: t is the time after adjustment (in seconds, e.g. what now() returns),
+    // and adjustmentn is number of seconds added. E.g., if we moved clock forward, we wanted to add seconds (+),
+    // and if we moved clock backwards, we wanted to remove extra seconds (-). Adjustment is absolute value of
+    // adjustment given by a human thru the clock menu (NOT weighted per day!). Returns new calibration value
+    // to use in the rtc chip.
+    char update(double t, double adjustment);
+
+    // get current calibration value.
+    char getCalib() {
+      return calib;
+    }
+
+    void reset();
+
+
+
+};
+
 #endif // ___ONLINESUM_H___