IF482 precision improvement

include/rtctime.h

@@ -23,6 +23,6 @@ float get_rtctemp(void);
 void IRAM_ATTR CLOCKIRQ();
 int timepulse_init(uint32_t pps_freq);
 void timepulse_start();
-uint8_t sync_clock(time_t t);
+time_t sync_clock(time_t t);
 
 #endif // _RTCTIME_H

src/gpsread.cpp

@@ -88,10 +88,11 @@ time_t tmConvert_t(uint16_t YYYY, uint8_t MM, uint8_t DD, uint8_t hh,
 
 // function to fetch current time from gps
 time_t get_gpstime(void) {
-  // never call now() in this function, this would cause a recursion!
+  // never call now() in this function, this would break this function
+  // to use as SyncProvider due to recursive call to now()
   time_t t = 0;
   if ((gps.time.age() < 1500) && (gps.time.isValid())) {
-    t = tmConvert_t(gps.date.year(), gps.date.month(), gps.date.day(),
+    t = 1 + tmConvert_t(gps.date.year(), gps.date.month(), gps.date.day(),
                     gps.time.hour(), gps.time.minute(), gps.time.second());
     ESP_LOGD(TAG, "GPS time: %4d/%02d/%02d %02d:%02d:%02d", year(t), month(t),
              day(t), hour(t), minute(t), second(t));

src/if482.cpp

@@ -115,19 +115,19 @@ int if482_init(void) {
                           "if482loop", // name of task
                           2048,        // stack size of task
                           (void *)1,   // parameter of the task
-                          3,           // priority of the task
+                          4,           // priority of the task
                           &ClockTask,  // task handle
                           0);          // CPU core
 
   assert(ClockTask); // has clock task started?
-  timepulse_start(); // start pulse
+  // timepulse_start(); // start pulse
 
   return 1; // success
 } // if482_init
 
 String IF482_Out(time_t tt) {
 
-  time_t t = myTZ.toLocal(tt);
+  time_t t = 1 + myTZ.toLocal(tt);
   char mon, buf[14], out[IF482_FRAME_SIZE];
 
   switch (timeStatus()) { // indicates if time has been set and recently synced
@@ -159,18 +159,32 @@ void if482_loop(void *pvParameters) {
 
   configASSERT(((uint32_t)pvParameters) == 1); // FreeRTOS check
 
+  time_t tOut;
   TickType_t wakeTime;
-  const TickType_t timeOffset =
+  const TickType_t tTx = tx_time(HAS_IF482); // duration of telegram transmit
-      tx_time(HAS_IF482); // duration of telegram transmit
-  const TickType_t startTime = xTaskGetTickCount(); // now
-
-  sync_clock(now());  // wait until begin of a new second
   BitsPending = true;                        // start blink in display
 
-  // take timestamp at moment of start of new second
+  // phase 1: sync task on top of second
-  const TickType_t shotTime = xTaskGetTickCount() - startTime - timeOffset;
 
-  // task remains in blocked state until it is notified by isr
+  sync_clock(now());
+
+  const TickType_t t0 = xTaskGetTickCount(); // moment of start top of second
+
+  timepulse_start(); // start timepulse
+
+  xTaskNotifyWait(
+      0x00,           // don't clear any bits on entry
+      ULONG_MAX,      // clear all bits on exit
+      &wakeTime,      // receives moment of call from isr
+      portMAX_DELAY); // wait forever (missing error handling here...)
+
+  const TickType_t tOffset = wakeTime - t0;
+  const TickType_t tShot =
+      (tOffset < tTx) ? (1000 - tOffset - tTx) : (tOffset - tTx);
+
+  ESP_LOGI(TAG, "IF482 signal synced with precision %dms", 1000 - tOffset);
+
+  // phase 2: sync task on time pulse interrupt
   for (;;) {
     xTaskNotifyWait(
         0x00,           // don't clear any bits on entry
@@ -178,22 +192,25 @@ void if482_loop(void *pvParameters) {
         &wakeTime,      // receives moment of call from isr
         portMAX_DELAY); // wait forever (missing error handling here...)
 
+    tOut = now() + 1; // next second after waketime
+
 // select clock scale
 #if (PPS == IF482_PULSE_DURATION) // we don't need clock rescaling
     // wait until it's time to start transmit telegram for next second
-    vTaskDelayUntil(&wakeTime, shotTime); // sets waketime to moment of shot
+    vTaskDelayUntil(&wakeTime, tShot); // sets waketime to moment of tShot
-    IF482.print(IF482_Out(now() + 1));
+    IF482.print(IF482_Out(tOut));
 
 #elif (PPS > IF482_PULSE_DURATION) // we need upclocking
     for (uint8_t i = 1; i <= PPS / IF482_PULSE_DURATION; i++) {
-      vTaskDelayUntil(&wakeTime, shotTime); // sets waketime to moment of shot
+      vTaskDelayUntil(&wakeTime, tShot); // sets waketime to moment of shot
-      IF482.print(IF482_Out(now() + 1));
+      IF482.print(IF482_Out(tOut));
     }
 
 #elif (PPS < IF482_PULSE_DURATION) // we need downclocking, not yet implemented
 #error Timepulse is too low for IF482!
 #endif
-  }
+  } // forever
+
 } // if482_loop()
 
 // helper function to calculate IF482 telegram serial tx time from serial

src/rtctime.cpp

@@ -1,5 +1,7 @@
 #include "rtctime.h"
 
+#define I2C_DELAY (12) // 12ms is i2c delay when saving time to RTC chip
+
 // Local logging tag
 static const char TAG[] = "main";
 
@@ -60,10 +62,12 @@ error:
 
 } // rtc_init()
 
-int set_rtctime(time_t t) { // t is epoch time starting 1.1.1970
+int set_rtctime(time_t t) { // t is seconds epoch time starting 1.1.1970
   if (I2C_MUTEX_LOCK()) {
-    Rtc.SetDateTime(RtcDateTime(t));
+    time_t tt = sync_clock(t); // wait for top of second
+    Rtc.SetDateTime(RtcDateTime(tt));
     I2C_MUTEX_UNLOCK(); // release i2c bus access
+    ESP_LOGI(TAG, "RTC calibrated");
     return 1; // success
   }
   return 0; // failure
@@ -176,15 +180,11 @@ void timepulse_start() {
 #endif
 }
 
-// helper function to sync phase of DCF output signal to start of second t
+// helper function to sync time_t of top of next second
-uint8_t sync_clock(time_t t) {
+time_t sync_clock(time_t t) {
-  time_t tt = t;
+  while (millis() % 1000)
-  // delay until start of next second
+    ; // wait for milli seconds to be zero before setting new time
-  do {
+  return (now());
-    tt = now();
-  } while (t == tt);
-  ESP_LOGI(TAG, "Sync on Sec %d", second(tt));
-  return second(tt);
 }
 
 // interrupt service routine triggered by either rtc pps or esp32 hardware