LoRaWAN-Signal-Mapping/iot/main/gps.cpp

#include <TinyGPS.h>

#include "gps.h"
#include "settings.h"
#include "power.h"
#include "storage.h"


SoftwareSerial gps_begin() {
	// FUTURE: If this doesn't work as expected, we may want to find a more reliable SoftwareSerial library
	SoftwareSerial serial_gps(PIN_GPS_RX, PIN_GPS_TX);
	// Initialise the software-based serial connection to the GPS device
	serial_gps.begin(BAUD_GPS);
	return serial_gps;
}

GPSLocation gps_fetch() {
	// The serial connection to the GPS module
	SoftwareSerial serial_gps = gps_begin();
	// The GPS message decoder
	TinyGPS	gps;
	// The struct that will hold the result
	GPSLocation result;
	
	Serial.print(F("[gps] Working "));
	uint32_t start = millis(), ms_last_update = millis();
	uint8_t ticks = 0;
	unsigned long fix_age = TinyGPS::GPS_INVALID_AGE;
	unsigned long chars;
	unsigned short sentences, failed_checksum;
	
	
	
	// We WILL discover our location - if it's the last thing we do!
	while(true) {
		gps.stats(&chars, &sentences, &failed_checksum);
		
		if(millis() - start > 5000 && chars < 10) {
			Serial.println(F("\n[error/gps] Init failed"));
			while(true) { delay(1); }
		}
		
		// Make sure there's something to read
		if(serial_gps.available() <= 0)
			continue;
		
		// If it failed, go around again
		if(!gps.encode(serial_gps.read()))
			continue;
		
		gps.f_get_position(&(result.lat), &(result.lng), &fix_age);
		
		// If we haven't acquired a lock yet, go around again
		if(fix_age == TinyGPS::GPS_INVALID_AGE) {
			// NOTE: It can take a rather long time to get a lock. Just wait patiently :-)
			if(millis() - ms_last_update > 500) {
				ticks++;
				Serial.print('.');
				if(ticks > 80) {
					Serial.println();
					ticks = 0;
				}
				ms_last_update = millis();
			}
			continue;
		}
		
		// Hooray!
		Serial.println(F("ok"));
		
		// gps.f_get_position pushes the values into result directly
		
		#ifdef GPS_DELTA_CHECK
		float last_reading_lat = store_eeprom_float_retrieve(sizeof(uint32_t) * 2);
		float last_reading_lng = store_eeprom_float_retrieve(sizeof(uint32_t) * 2 + sizeof(float));
		// Serial.println(last_reading_lat);
		// Serial.println(last_reading_lng);
		// Serial.println(result.lat);
		// Serial.println(result.lng);
		if(abs(last_reading_lat - result.lat) < GPS_DELTA_MIN_LAT &&
			abs(last_reading_lng - result.lng) < GPS_DELTA_MIN_LNG &&
			last_reading_lat == last_reading_lat && // Ensure that the last readings aren't NaN
			last_reading_lng == last_reading_lng) {
			Serial.println(F("[gps] No movement detected"));
			power_off();
		}
		
		// Save this location to EEPROM
		store_eeprom_float_save(sizeof(uint32_t) * 2, result.lat);
		store_eeprom_float_save(sizeof(uint32_t) * 2 + sizeof(float), result.lng);
		#endif
		
		// TODO: Don't send a message at night
		#ifdef SD_DEBUG_ENABLED
		int year;
		byte month, day, hour, minute, second, _hundredths;
		gps.crack_datetime(&year, &month, &day, &hour, &minute, &second, &_hundredths, &fix_age);
		
		snprintf(result.time, 19, "%04d-%02d-%02d %02d:%02d:%02d",
			year, month, day,
			hour, minute, second
		);
		#endif
		return result;
	}
	
	gps_end(serial_gps);
}

void gps_end(SoftwareSerial serial_gps) {
	serial_gps.end();
}