LibrePilot/flight/Modules/GPS/GPS.c

/**
 ******************************************************************************
 * @addtogroup OpenPilotModules OpenPilot Modules
 * @{ 
 * @addtogroup GSPModule GPS Module
 * @brief Process GPS information
 * @{ 
 *
 * @file       GPS.c
 * @author     The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
 * @brief      GPS module, handles GPS and NMEA stream
 * @see        The GNU Public License (GPL) Version 3
 *
 *****************************************************************************/
/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "openpilot.h"
#include "GPS.h"
#include <stdbool.h>
#include "NMEA.h"
#include "gpsposition.h"
#include "homelocation.h"
#include "gpstime.h"
#include "WorldMagModel.h"
#include "CoordinateConversions.h"

// constants/macros/typdefs
#define NMEA_BUFFERSIZE		128

#define GPS_TIMEOUT_MS 500

// Private functions

static void gpsTask(void *parameters);
static void setHomeLocation(GPSPositionData * gpsData);

// Global variables

// Private constants
// Unfortunately need a good size stack for the WMM calculation
#define STACK_SIZE_BYTES 800
#define TASK_PRIORITY (tskIDLE_PRIORITY + 1)

// Private types

// Private variables
static uint32_t    gpsPort;
static xTaskHandle gpsTaskHandle;
static char gps_rx_buffer[NMEA_BUFFERSIZE];

static uint32_t timeOfLastUpdateMs;
static uint32_t numUpdates;
static uint32_t numChecksumErrors;
static uint32_t numParsingErrors;

/**
 * Initialise the gps module
 * \return -1 if initialisation failed
 * \return 0 on success
 */
int32_t GPSInitialize(void)
{
	signed portBASE_TYPE xReturn;

	// TODO: Get gps settings object
	gpsPort = PIOS_COM_GPS;

	// Start gps task
	xReturn = xTaskCreate(gpsTask, (signed char *)"GPS", STACK_SIZE_BYTES/4, NULL, TASK_PRIORITY, &gpsTaskHandle);
	TaskMonitorAdd(TASKINFO_RUNNING_GPS, gpsTaskHandle);

	return 0;
}

/**
 * gps task. Processes input buffer. It does not return.
 */
static void gpsTask(void *parameters)
{
	int32_t gpsRxOverflow = 0;
	char c;
	portTickType xDelay = 100 / portTICK_RATE_MS;
	GPSPositionData GpsData;
	uint32_t timeNowMs;
	
	bool start_flag = false;
	bool found_cr = false;
	uint8_t rx_count = 0;
	
	//#define	DISABLE_GPS_TRESHOLD
	//#define	ENABLE_GPS_ONESENTENCE
	//#define	ENABLE_DEFAULT_NMEA
	
#ifdef DISABLE_GPS_TRESHOLD
	PIOS_COM_SendStringNonBlocking(gpsPort,"$PMTK397,0*23\r\n");
#endif
#ifdef ENABLE_GPS_ONESENTENCE
	PIOS_COM_SendStringNonBlocking(gpsPort,"$PGCMD,21,2*6C\r\n");
#endif
#ifdef ENABLE_DEFAULT_NMEA
	PIOS_COM_SendStringNonBlocking(gpsPort,"$PGCMD,21,3*6D\r\n");
#endif
	
	// Loop forever
	while (1) {
		/* This blocks the task until there is something on the buffer */
		while (PIOS_COM_ReceiveBufferUsed(gpsPort) > 0) {
			
			c = PIOS_COM_ReceiveBuffer(gpsPort);
			
			/* detect start while acquiring stream */
			if(!start_flag && (c == '$')) {
				start_flag = true;
				found_cr = false;
				rx_count = 0;
			} else if (!start_flag)
				continue;
			
			if(rx_count >= NMEA_BUFFERSIZE) {
				/* 
				 * The buffer is already full and we haven't found a valid NMEA sentence.
				 * Flush the buffer and note the overflow event.
				 */
				gpsRxOverflow++;
				start_flag = false;
				found_cr = false;
				rx_count = 0;
			} else {
				gps_rx_buffer[rx_count] = c;
				rx_count++;
			}
			
			
			/* look for ending '\r\n' sequence */
			if (!found_cr && (c == '\r') )
				found_cr = true; 
			else if (found_cr && (c != '\n') )
				found_cr = false;  // false end flag
			else if (found_cr && (c == '\n') ) {
				
				/* prepare to parse next sentence */				
				start_flag = false;
				found_cr = false;
				rx_count = 0;
				
				/*
				 * Our rxBuffer must look like this now:
				 *   [0]           = '$'
				 *   ...           = zero or more bytes of sentence payload
				 *   [end_pos - 1] = '\r'
				 *   [end_pos]     = '\n'
				 *
				 * Prepare to consume the sentence from the buffer
				 */
				
				/* Validate the checksum over the sentence */
				if (!NMEA_checksum(&gps_rx_buffer[1])) {
					/* Invalid checksum.  May indicate dropped characters on Rx. */
					++numChecksumErrors;
				} else {
					/* Valid checksum, use this packet to update the GPS position */
					if (!NMEA_update_position(&gps_rx_buffer[1])) {
						++numParsingErrors;
					} else {
						++numUpdates;
					}
					timeOfLastUpdateMs = xTaskGetTickCount() * portTICK_RATE_MS;
				}
			}
		}

		// Check for GPS timeout
		timeNowMs = xTaskGetTickCount() * portTICK_RATE_MS;
		if ((timeNowMs - timeOfLastUpdateMs) > GPS_TIMEOUT_MS) {
			GPSPositionGet(&GpsData);
			GpsData.Status = GPSPOSITION_STATUS_NOGPS;
			GPSPositionSet(&GpsData);
			AlarmsSet(SYSTEMALARMS_ALARM_GPS, SYSTEMALARMS_ALARM_ERROR);
		} else {
			// Had an update
			HomeLocationData home;
			HomeLocationGet(&home);

			GPSPositionGet(&GpsData);
			if ((GpsData.Status == GPSPOSITION_STATUS_FIX3D) && (home.Set == HOMELOCATION_SET_FALSE)) {
				setHomeLocation(&GpsData);
			}

			//criteria for GPS-OK taken from this post...
			//http://forums.openpilot.org/topic/1523-professors-insgps-in-svn/page__view__findpost__p__5220
			if ((GpsData.PDOP<3.5)&&(GpsData.Satellites>=7))AlarmsClear(SYSTEMALARMS_ALARM_GPS);
			else if (GpsData.Status == GPSPOSITION_STATUS_FIX3D) AlarmsSet(SYSTEMALARMS_ALARM_GPS, SYSTEMALARMS_ALARM_WARNING);
			else AlarmsSet(SYSTEMALARMS_ALARM_GPS, SYSTEMALARMS_ALARM_CRITICAL);
		}

		// Block task until next update
		vTaskDelay(xDelay);
	}
}

static void setHomeLocation(GPSPositionData * gpsData)
{
	HomeLocationData home;
	HomeLocationGet(&home);
	GPSTimeData gps;
	GPSTimeGet(&gps);

	if (gps.Year >= 2000) {
		// Store LLA
		home.Latitude = gpsData->Latitude;
		home.Longitude = gpsData->Longitude;
		home.Altitude = gpsData->Altitude + gpsData->GeoidSeparation;

		// Compute home ECEF coordinates and the rotation matrix into NED
		double LLA[3] = { ((double)home.Latitude) / 10e6, ((double)home.Longitude) / 10e6, ((double)home.Altitude) };
		double ECEF[3];
		RneFromLLA(LLA, (float (*)[3])home.RNE);
		LLA2ECEF(LLA, ECEF);
		// TODO: Currently UAVTalk only supports float but these conversions use double
		// need to find out if they require that precision and if so extend UAVTAlk
		home.ECEF[0] = (int32_t) (ECEF[0] * 100);
		home.ECEF[1] = (int32_t) (ECEF[1] * 100);
		home.ECEF[2] = (int32_t) (ECEF[2] * 100);

		// Compute magnetic flux direction at home location
		if (WMM_GetMagVector(LLA[0], LLA[1], LLA[2], gps.Month, gps.Day, gps.Year, &home.Be[0]) >= 0)
		{   // calculations appeared to go OK

		    home.Set = HOMELOCATION_SET_TRUE;
		    HomeLocationSet(&home);
		}
	}
}

/** 
  * @}
  * @}
  */