improve RTC accuracy

include/globals.h

@@ -111,6 +111,5 @@ typedef struct {
 } sdsStatus_t;
 
 extern char clientId[20];   // unique clientID
-extern time_t _COMPILETIME; // epoch build time
 
 #endif

include/rtctime.h

@@ -12,7 +12,7 @@ extern RtcDS3231<TwoWire> Rtc; // make RTC instance globally available
 uint8_t rtc_init(void);
 uint8_t set_rtctime(time_t t);
 void sync_rtctime(void);
-time_t get_rtctime(void);
+time_t get_rtctime(uint16_t *msec);
 float get_rtctemp(void);
 
 #endif // _RTCTIME_H

include/timekeeper.h

@@ -33,7 +33,7 @@ bool timeIsValid(time_t const t);
 void calibrateTime(void);
 void IRAM_ATTR setMyTime(uint32_t t_sec, uint16_t t_msec,
                          timesource_t mytimesource);
-time_t compileTime(const String compile_date);
+time_t compileTime(void);
 time_t mkgmtime(const struct tm *ptm);
 TickType_t tx_Ticks(uint32_t framesize, unsigned long baud, uint32_t config,
                     int8_t rxPin, int8_t txPins);

src/main.cpp

@@ -27,24 +27,22 @@ licenses. Refer to LICENSE.txt file in repository for more details.
 
 Task          	Core  Prio  Purpose
 -------------------------------------------------------------------------------
-ledloop       0     3     blinks LEDs
+ledloop*      	0     3     blinks LEDs
-spiloop       0     2     reads/writes data on spi interface
+spiloop#      	0     2     reads/writes data on spi interface
-IDLE          0     0     ESP32 arduino scheduler -> runs wifi sniffer
+lmictask*     	1     2     MCCI LMiC LORAWAN stack
+clockloop#    	1     4     generates realtime telegrams for external clock
+mqttloop#     	1     2     reads/writes data on ETH interface
+timesync_proc#	1     3     processes realtime time sync requests
+irqhandler#   	1     2     cyclic tasks (i.e. displayrefresh) triggered by
+timers gpsloop*      	1     1     reads data from GPS via serial or i2c
+lorasendtask# 	1     1     feeds data from lora sendqueue to lmcic
+rmcd_process# 	1     1     Remote command interpreter loop
 
-lmictask      1     2     MCCI LMiC LORAWAN stack
+* spinning task
-clockloop     1     4     generates realtime telegrams for external clock
+# blocked/waiting task
-mqttloop      1     2     reads/writes data on ETH interface
-timesync_proc 1     3     processes realtime time sync requests
-irqhandler    1     2     cyclic tasks (i.e. displayrefresh) triggered by timers
-gpsloop       1     1     reads data from GPS via serial or i2c
-lorasendtask  1     1     feeds data from lora sendqueue to lmcic
-rmcd_process  1     1     Remote command interpreter loop
-IDLE          1     0     ESP32 arduino scheduler -> runs wifi channel rotator
 
 Low priority numbers denote low priority tasks.
-
+-------------------------------------------------------------------------------
-NOTE: Changing any timings will have impact on time accuracy of whole code.
-So don't do it if you do not own a digital oscilloscope.
 
 // ESP32 hardware timers
 -------------------------------------------------------------------------------
@@ -126,7 +124,7 @@ void setup() {
   snprintf(clientId, 20, "paxcounter_%08x", hashedmac);
   ESP_LOGI(TAG, "Starting %s v%s (runmode=%d / restarts=%d)", clientId,
            PROGVERSION, RTC_runmode, RTC_restarts);
-  ESP_LOGI(TAG, "code build date: %d", _COMPILETIME);
+  ESP_LOGI(TAG, "code build date: %d", compileTime());
 
   // print chip information on startup if in verbose mode after coldstart
 #if (VERBOSE)
@@ -494,8 +492,7 @@ void setup() {
   cyclicTimer.attach(HOMECYCLE, setCyclicIRQ);
 
 // only if we have a timesource we do timesync
-#if ((TIME_SYNC_LORAWAN) || (TIME_SYNC_LORASERVER) || (HAS_GPS) ||             \
+#if ((TIME_SYNC_LORAWAN) || (TIME_SYNC_LORASERVER) || (HAS_GPS) || (HAS_RTC))
-     defined HAS_RTC)
 
 #if (defined HAS_IF482 || defined HAS_DCF77)
   ESP_LOGI(TAG, "Starting Clock Controller...");

src/rtctime.cpp

@@ -25,14 +25,14 @@ uint8_t rtc_init(void) {
     }
 
 #if (TIME_SYNC_COMPILEDATE)
-    // initialize a blank RTC without battery backup with compiled time
+    // initialize a blank RTC without battery backup with build time
     RtcDateTime tt = Rtc.GetDateTime();
     time_t t = tt.Epoch32Time(); // sec2000 -> epoch
 
     if (!Rtc.IsDateTimeValid() || !timeIsValid(t)) {
-      ESP_LOGW(TAG, "RTC has no recent time, setting to compiled time");
+      ESP_LOGW(TAG, "RTC has no recent time, setting to compiletime");
-      Rtc.SetDateTime(
+      Rtc.SetDateTime(RtcDateTime(mkgmtime(compileTime()) -
-          RtcDateTime(_COMPILETIME - SECS_YR_2000)); // epoch -> sec2000
+                                  SECS_YR_2000)); // epoch -> sec2000
     }
 #endif
 
@@ -62,15 +62,23 @@ uint8_t set_rtctime(time_t t) { // t is sec epoch time
   }
 } // set_rtctime()
 
-time_t get_rtctime(void) {
+time_t get_rtctime(uint16_t *msec) {
   time_t t = 0;
+  *msec = 0;
   if (I2C_MUTEX_LOCK()) {
     if (Rtc.IsDateTimeValid() && Rtc.GetIsRunning()) {
       RtcDateTime tt = Rtc.GetDateTime();
       t = tt.Epoch32Time(); // sec2000 -> epoch
     }
     I2C_MUTEX_UNLOCK();
-    return timeIsValid(t);
+#ifdef RTC_INT
+    // adjust time to top of next second by waiting TimePulseTick to flip
+    bool lastTick = TimePulseTick;
+    while (TimePulseTick == lastTick) {
+    };
+    t++;
+#endif
+    return t;
   } else {
     ESP_LOGE(TAG, "RTC get time failure");
     return 0; // failure

src/timekeeper.cpp

@@ -21,7 +21,6 @@ const char timeSetSymbols[] = {'G', 'R', 'L', '*', '?'};
 
 bool volatile TimePulseTick = false;
 timesource_t timeSource = _unsynced;
-time_t _COMPILETIME = compileTime(__DATE__);
 TaskHandle_t ClockTask = NULL;
 hw_timer_t *ppsIRQ = NULL;
 
@@ -40,8 +39,7 @@ Ticker timesyncer;
 void setTimeSyncIRQ() { xTaskNotify(irqHandlerTask, TIMESYNC_IRQ, eSetBits); }
 
 void calibrateTime(void) {
-  ESP_LOGD(TAG, "[%0.3f] calibrateTime, timeSource == %d", _seconds(),
+
-           timeSource);
   time_t t = 0;
   uint16_t t_msec = 0;
 
@@ -57,7 +55,7 @@ void calibrateTime(void) {
 
 // has RTC -> fallback to RTC time
 #ifdef HAS_RTC
-    t = get_rtctime();
+    t = get_rtctime(&t_msec);
     // set time from RTC - method will check if time is valid
     setMyTime((uint32_t)t, t_msec, _rtc);
 #endif
@@ -101,26 +99,27 @@ void IRAM_ATTR setMyTime(uint32_t t_sec, uint16_t t_msec,
       vTaskDelay(pdMS_TO_TICKS(1000 - t_msec % 1000));
     }
 
+    // from here on we are on top of next second
+
     tv.tv_sec = time_to_set;
     tv.tv_usec = 0;
     sntp_sync_time(&tv);
 
     ESP_LOGI(TAG, "[%0.3f] UTC time: %d.000 sec", _seconds(), time_to_set);
 
-    // if we have a software pps timer, shift it to top of second
+    // if we have a precise time timesource, set RTC time and shift RTC_INT
-    if (ppsIRQ != NULL) {
+    // pulse to top of second
-
-      timerWrite(ppsIRQ, 0); // reset pps timer
-      CLOCKIRQ();            // fire clock pps, this advances time 1 sec
-    }
-
-// if we have got an external timesource, set RTC time and shift RTC_INT pulse
-// to top of second
 #ifdef HAS_RTC
     if ((mytimesource == _gps) || (mytimesource == _lora))
       set_rtctime(time_to_set);
 #endif
 
+    // if we have a software pps timer, shift it to top of second
+    if (ppsIRQ != NULL) {
+      timerWrite(ppsIRQ, 0); // reset pps timer
+      CLOCKIRQ();            // fire clock pps to advance wall clock by 1 sec
+    }
+
     timeSource = mytimesource; // set global variable
 
     timesyncer.attach(TIME_SYNC_INTERVAL * 60, setTimeSyncIRQ);
@@ -132,7 +131,7 @@ void IRAM_ATTR setMyTime(uint32_t t_sec, uint16_t t_msec,
              "[%0.3f] Failed to synchronise time from source %c | unix sec "
              "obtained from source: %d | unix sec at program compilation: %d",
              _seconds(), timeSetSymbols[mytimesource], time_to_set,
-             _COMPILETIME);
+             compileTime());
   }
 }
 
@@ -224,7 +223,9 @@ void IRAM_ATTR CLOCKIRQ(void) {
 // helper function to check plausibility of a given epoch time
 bool timeIsValid(time_t const t) {
   // is t a time in the past? we use compile time to guess
-  return (t > _COMPILETIME);
+  // compile time is some local time, but we do not know it's time zone
+  // thus, we go 1 full day back to be sure to catch a time in the past
+  return (t > (compileTime() - 86400));
 }
 
 // helper function to calculate serial transmit time
@@ -283,7 +284,7 @@ void clock_loop(void *taskparameter) { // ClockTask
     // set calendar time for next second of clock output
     tt = (time_t)(current_time + 1);
     localtime_r(&tt, &t);
-    mktime(&t);
+    tt = mktime(&t);
 
 #if defined HAS_IF482
 
@@ -293,13 +294,13 @@ void clock_loop(void *taskparameter) { // ClockTask
     if (xTaskNotifyWait(0x00, ULONG_MAX, &current_time, txDelay) == pdTRUE) {
       tt = (time_t)(current_time + 1);
       localtime_r(&tt, &t);
-      mktime(&t);
+      tt = mktime(&t);
     }
 
     // send IF482 telegram
-    IF482.print(IF482_Frame(t)); // note: telegram is for *next* second
+    IF482.print(IF482_Frame(tt)); // note: telegram is for *next* second
 
-    ESP_LOGD(TAG, "[%0.3f] IF482: %s", _seconds(), IF482_Frame(t));
+    ESP_LOGD(TAG, "[%0.3f] IF482: %s", _seconds(), IF482_Frame(tt).c_str());
 
 #elif defined HAS_DCF77
 
@@ -340,7 +341,7 @@ void clock_loop(void *taskparameter) { // ClockTask
 } // clock_loop()
 
 // we use compile date to create a time_t reference "in the past"
-time_t compileTime(const String compile_date) {
+time_t compileTime(void) {
 
   char s_month[5];
   int year;
@@ -353,10 +354,11 @@ time_t compileTime(const String compile_date) {
   if (secs == -1) {
 
     // determine date
-    // we go one day back to bypass unknown timezone of local time
+    sscanf(__DATE__, "%s %d %d", s_month, &t.tm_mday, &year);
-    sscanf(compile_date.c_str(), "%s %d %d", s_month, &t.tm_mday - 1, &year);
     t.tm_mon = (strstr(month_names, s_month) - month_names) / 3;
     t.tm_year = year - 1900;
+    // determine time
+    sscanf(__TIME__, "%d:%d:%d", &t.tm_hour, &t.tm_min, &t.tm_sec);
 
     // convert to secs local time
     secs = mktime(&t);