GPS IRQ added to increase gps time sync accuracy

include/globals.h

@@ -83,6 +83,7 @@ typedef struct {
   uint8_t satellites;
   uint16_t hdop;
   int16_t altitude;
+  time_t utctime;
 } gpsStatus_t;
 
 typedef struct {
@@ -111,12 +112,13 @@ extern uint16_t volatile macs_total, macs_wifi, macs_ble,
     batt_voltage;                   // display values
 extern bool volatile TimePulseTick; // 1sec pps flag set by GPS or RTC
 extern timesource_t timeSource;
-extern hw_timer_t *displayIRQ, *ppsIRQ;
+extern hw_timer_t *displayIRQ, *ppsIRQ, *gpsIRQ;
 extern SemaphoreHandle_t I2Caccess;
 extern TaskHandle_t irqHandlerTask, ClockTask;
 extern TimerHandle_t WifiChanTimer;
 extern Timezone myTZ;
 extern time_t userUTCTime;
+extern time_t volatile gps_pps_time;
 
 // application includes
 #include "led.h"

include/irqhandler.h

@@ -8,7 +8,7 @@
 #define TIMESYNC_IRQ 0x10
 #define MASK_IRQ 0x20
 #define UNMASK_IRQ 0x40
-#define RESERVED_IRQ 0x80
+#define GPS_IRQ 0x80
 
 #include "globals.h"
 #include "cyclic.h"
@@ -27,4 +27,8 @@ void IRAM_ATTR DisplayIRQ();
 void IRAM_ATTR ButtonIRQ();
 #endif
 
+#if (HAS_GPS)
+void IRAM_ATTR GpsIRQ();
+#endif
+
 #endif

src/gpsread.cpp

@@ -11,9 +11,10 @@ TaskHandle_t GpsTask;
 
 #ifdef GPS_SERIAL
 HardwareSerial GPS_Serial(1); // use UART #1
-static TickType_t gps_txDelay = tx_Ticks(NMEA_FRAME_SIZE, GPS_SERIAL);
+static uint16_t nmea_txDelay_ms =
+    tx_Ticks(NMEA_FRAME_SIZE, GPS_SERIAL) / portTICK_PERIOD_MS;
 #else
-static TickType_t gps_txDelay = 0;
+static uint16_t nmea_txDelay_ms = 0;
 #endif
 
 // initialize and configure GPS
@@ -71,37 +72,24 @@ void gps_read() {
   gps_status.satellites = (uint8_t)gps.satellites.value();
   gps_status.hdop = (uint16_t)gps.hdop.value();
   gps_status.altitude = (int16_t)gps.altitude.meters();
+  gps_status.utctime = get_gpstime();
+
   // show NMEA data in debug mode, useful for debugging GPS
-  ESP_LOGD(TAG, "GPS NMEA data: passed %d / failed: %d / with fix: %d",
+  ESP_LOGV(TAG, "GPS NMEA data: passed %d / failed: %d / with fix: %d",
            gps.passedChecksum(), gps.failedChecksum(), gps.sentencesWithFix());
 }
 
 // function to fetch current time from gps
 time_t get_gpstime(void) {
 
-  // set time to wait for arrive next recent NMEA time record
-  static const uint32_t gpsDelay_ms = 1000 - gps_txDelay / portTICK_PERIOD_MS;
-
   time_t t = 0;
   uint32_t time_age = gps.time.age();
 
-  if ((time_age < gpsDelay_ms) && gps.time.isValid() && gps.date.isValid() &&
+  if (gps.time.isValid() && gps.date.isValid() && (time_age < 1000))
-      gps.time.isUpdated()) {
-
     t = tmConvert(gps.date.year(), gps.date.month(), gps.date.day(),
                   gps.time.hour(), gps.time.minute(), gps.time.second());
 
-    if (time_age < (gpsDelay_ms / 2))
+  return timeIsValid(time_age > nmea_txDelay_ms ? t : t - 1);
-      t--;
-
-    ESP_LOGD(TAG, "GPS time age: %dms", time_age);
-
-#ifndef GPS_INT
-    // wait until top of second with millisecond precision
-    vTaskDelay(pdMS_TO_TICKS(1000 - time_age) - gps_txDelay);
-#endif
-  }
-  return timeIsValid(t);
 } // get_gpstime()
 
 // GPS serial feed FreeRTos Task

src/irqhandler.cpp

@@ -39,6 +39,12 @@ void irqHandler(void *pvParameters) {
       refreshtheDisplay();
 #endif
 
+// gps refresh buffer?
+#if (HAS_GPS)
+    if (InterruptStatus & GPS_IRQ)
+      gps_read();
+#endif
+
     // are cyclic tasks due?
     if (InterruptStatus & CYCLIC_IRQ)
       doHousekeeping();
@@ -47,7 +53,6 @@ void irqHandler(void *pvParameters) {
     // is time to be synced?
     if (InterruptStatus & TIMESYNC_IRQ) {
       time_t t = timeProvider();
-      ESP_LOGD(TAG, "Sync time = %d", t);
       if (timeIsValid(t))
         setTime(t);
     }
@@ -85,6 +90,17 @@ void IRAM_ATTR ButtonIRQ() {
 }
 #endif
 
+#if (HAS_GPS)
+void IRAM_ATTR GpsIRQ() {
+  BaseType_t xHigherPriorityTaskWoken = pdFALSE;
+
+  xTaskNotifyFromISR(irqHandlerTask, GPS_IRQ, eSetBits,
+                     &xHigherPriorityTaskWoken);
+  if (xHigherPriorityTaskWoken)
+    portYIELD_FROM_ISR();
+}
+#endif
+
 int mask_user_IRQ() {
   // begin of time critical section: lock I2C bus to ensure accurate timing
   if (!I2C_MUTEX_LOCK())

src/main.cpp

@@ -51,7 +51,7 @@ So don't do it if you do not own a digital oscilloscope.
 -------------------------------------------------------------------------------
 0	displayIRQ -> display refresh -> 40ms (DISPLAYREFRESH_MS)
 1 ppsIRQ -> pps clock irq -> 1sec
-2	unused
+2	gpsIRQ -> gps store data -> 500ms
 3	unused
 
 
@@ -61,6 +61,7 @@ So don't do it if you do not own a digital oscilloscope.
 fired by hardware
 DisplayIRQ      -> esp32 timer 0  -> irqHandlerTask (Core 1)
 CLOCKIRQ        -> esp32 timer 1  -> ClockTask (Core 1)
+GpsIRQ          -> esp32 timer 2  -> irqHandlerTask (Core 1)
 ButtonIRQ       -> external gpio  -> irqHandlerTask (Core 1)
 
 fired by software (Ticker.h)
@@ -84,11 +85,12 @@ uint8_t volatile channel = 0;              // channel rotation counter
 uint16_t volatile macs_total = 0, macs_wifi = 0, macs_ble = 0,
                   batt_voltage = 0; // globals for display
 
-hw_timer_t *ppsIRQ = NULL, *displayIRQ = NULL;
+hw_timer_t *ppsIRQ = NULL, *displayIRQ = NULL, *gpsIRQ = NULL;
 
 TaskHandle_t irqHandlerTask = NULL, ClockTask = NULL;
 SemaphoreHandle_t I2Caccess;
 bool volatile TimePulseTick = false;
+time_t volatile gps_pps_time = 0;
 time_t userUTCTime = 0;
 timesource_t timeSource = _unsynced;
 
@@ -408,6 +410,14 @@ void setup() {
   timerAlarmEnable(displayIRQ);
 #endif
 
+ // gps buffer read interrupt
+#if (HAS_GPS)
+  gpsIRQ = timerBegin(2, 80, true);
+  timerAttachInterrupt(gpsIRQ, &GpsIRQ, true);
+  timerAlarmWrite(gpsIRQ, 500 * 1000, true);
+  timerAlarmEnable(gpsIRQ);
+#endif
+
   // cyclic function interrupts
   sendcycler.attach(SENDCYCLE * 2, sendcycle);
   housekeeper.attach(HOMECYCLE, housekeeping);

src/rcommand.cpp

@@ -253,7 +253,6 @@ void get_status(uint8_t val[]) {
 void get_gps(uint8_t val[]) {
   ESP_LOGI(TAG, "Remote command: get gps status");
 #if(HAS_GPS)
-  gps_read();
   payload.reset();
   payload.addGPS(gps_status);
   SendPayload(GPSPORT, prio_high);

src/senddata.cpp

@@ -87,7 +87,6 @@ void sendCounter() {
     case GPS_DATA:
       // send GPS position only if we have a fix
       if (gps.location.isValid()) {
-        gps_read();
         payload.reset();
         payload.addGPS(gps_status);
         SendPayload(GPSPORT, prio_high);

src/timekeeper.cpp

@@ -27,7 +27,7 @@ time_t timeProvider(void) {
   time_t t = 0;
 
 #if (HAS_GPS)
-  t = get_gpstime(); // fetch recent time from last NEMA record
+  t = gps_pps_time; // fetch recent time from last NEMA record
   if (t) {
 #ifdef HAS_RTC
     set_rtctime(t, do_mutex); // calibrate RTC
@@ -106,6 +106,7 @@ uint8_t timepulse_init() {
 } // timepulse_init
 
 void timepulse_start(void) {
+
 #ifdef GPS_INT // start external clock gps pps line
   attachInterrupt(digitalPinToInterrupt(GPS_INT), CLOCKIRQ, RISING);
 #elif defined RTC_INT // start external clock rtc
@@ -114,9 +115,14 @@ void timepulse_start(void) {
   timerAttachInterrupt(ppsIRQ, &CLOCKIRQ, true);
   timerAlarmEnable(ppsIRQ);
 #endif
-  now(); // refresh sysTime to pps
+
+#if (HAS_GPS)
+  gps_read();
+  gps_pps_time = gps_status.utctime;
+#endif
 
   // start cyclic time sync
+  now();      // ensure sysTime is ßrecent
   timeSync(); // init systime by RTC or GPS or LORA
   timesyncer.attach(TIME_SYNC_INTERVAL * 60, timeSync);
 }
@@ -126,13 +132,20 @@ void IRAM_ATTR CLOCKIRQ(void) {
 
   BaseType_t xHigherPriorityTaskWoken = pdFALSE;
 
-  SyncToPPS(); // calibrates UTC systime and advances it +1, see microTime.h
+  SyncToPPS(); // advance systime, see microTime.h
 
+  // store recent gps time, if we have
+#if (HAS_GPS)
+  gps_pps_time = gps_status.utctime + 1;
+#endif
+
+// advance wall clock, if we have
 #if (defined HAS_IF482 || defined HAS_DCF77)
   xTaskNotifyFromISR(ClockTask, uint32_t(now()), eSetBits,
                      &xHigherPriorityTaskWoken);
 #endif
 
+// flip time pulse ticker, if needed
 #ifdef HAS_DISPLAY
 #if (defined GPS_INT || defined RTC_INT)
   TimePulseTick = !TimePulseTick; // flip pulse ticker

src/timesync.cpp

@@ -216,8 +216,12 @@ int recv_timesync_ans(uint8_t seq_no, uint8_t buf[], uint8_t buf_len) {
 // adjust system time, calibrate RTC and RTC_INT pps
 void IRAM_ATTR setMyTime(uint32_t t_sec, uint16_t t_msec) {
 
-  // advance time 1 sec wait time
+  time_t time_to_set = (time_t)t_sec;
-  time_t time_to_set = (time_t)(t_sec + 1);
+
+// advance time 1 sec wait time if we have no pulse clock
+#if (!defined GPS_INT) && (!defined RTC_INT)
+  time_to_set++;
+#endif
 
   ESP_LOGD(TAG, "[%0.3f] Calculated UTC epoch time: %d.%03d sec",
            millis() / 1000.0, time_to_set, t_msec);