ESP32-PaxCounter/src/gpsread.cpp

#ifdef HAS_GPS

#include "globals.h"

// Local logging tag
static const char TAG[] = "main";

TinyGPSPlus gps;
gpsStatus_t gps_status;
TaskHandle_t GpsTask;

#ifdef GPS_SERIAL
HardwareSerial GPS_Serial(1); // use UART #1
#endif

// initialize and configure GPS
int gps_init(void) {

  int ret = 1;

#if defined GPS_SERIAL
  GPS_Serial.begin(GPS_SERIAL);
  ESP_LOGI(TAG, "Using serial GPS");
#elif defined GPS_I2C
  Wire.begin(GPS_I2C, 400000); // I2C connect to GPS device with 400 KHz
  Wire.beginTransmission(GPS_ADDR);
  Wire.write(0x00);             // dummy write
  ret = Wire.endTransmission(); // check if chip is seen on i2c bus

  if (ret) {
    ESP_LOGE(TAG,
             "Quectel L76 GPS chip not found on i2c bus, bus error %d. "
             "Stopping GPS-Task.",
             ret);
    ret = 0;
  } else {
    ESP_LOGI(TAG, "Quectel L76 GPS chip found");
  }
#endif

  return ret;
} // gps_init()

// read GPS data and cast to global struct
void gps_read() {
  gps_status.latitude = (int32_t)(gps.location.lat() * 1e6);
  gps_status.longitude = (int32_t)(gps.location.lng() * 1e6);
  gps_status.satellites = (uint8_t)gps.satellites.value();
  gps_status.hdop = (uint16_t)gps.hdop.value();
  gps_status.altitude = (int16_t)gps.altitude.meters();
  // show NMEA data in debug mode, useful for debugging GPS
  ESP_LOGD(TAG, "GPS NMEA data: passed %d / failed: %d / with fix: %d",
           gps.passedChecksum(), gps.failedChecksum(), gps.sentencesWithFix());
}

// helper function to convert gps date/time into time_t
time_t tmConvert_t(uint16_t YYYY, uint8_t MM, uint8_t DD, uint8_t hh,
                   uint8_t mm, uint8_t ss) {
  tmElements_t tm;
  tm.Year = YYYY - 1970; // note year argument is offset from 1970 in time.h
  tm.Month = MM;
  tm.Day = DD;
  tm.Hour = hh;
  tm.Minute = mm;
  tm.Second = ss;
  return makeTime(tm);
}

// function to fetch current time from gps
time_t get_gpstime(void) {
  // never call now() in this function, this would cause a recursion!
  time_t t = 0;
  if ((gps.time.age() < 1500) && (gps.time.isValid())) {
    t = 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: %d/%d/%d %d:%d:%d", year(t), month(t), day(t),
             hour(t), minute(t), second(t));
  } else {
    ESP_LOGW(TAG, "GPS has no confident time");
  }
  return t;
} // get_gpstime()

// GPS serial feed FreeRTos Task
void gps_loop(void *pvParameters) {

  configASSERT(((uint32_t)pvParameters) == 1); // FreeRTOS check

  while (1) {

    if (cfg.payloadmask && GPS_DATA) {
#if defined GPS_SERIAL
      // feed GPS decoder with serial NMEA data from GPS device
      while (GPS_Serial.available()) {
        gps.encode(GPS_Serial.read());
      }
#elif defined GPS_I2C
      Wire.requestFrom(GPS_ADDR, 32); // caution: this is a blocking call
      while (Wire.available()) {
        gps.encode(Wire.read());
        delay(2); // 2ms delay according L76 datasheet
      }
#endif
    } // if

    delay(2); // yield to CPU

  } // end of infinite loop

  vTaskDelete(GpsTask); // shoud never be reached

} // gps_loop()

#endif // HAS_GPS