/*! \file nmea.c \brief NMEA protocol function library. */

//*****************************************************************************

//

// File Name : 'nmea.c'

// Title : NMEA protocol function library

// Author : Pascal Stang - Copyright (C) 2002

// Created : 2002.08.27

// Revised : 2002.08.27

// Version : 0.1

// Target MCU : Atmel AVR Series

// Editor Tabs : 4

//

// NOTE: This code is currently below version 1.0, and therefore is considered

// to be lacking in some functionality or documentation, or may not be fully

// tested. Nonetheless, you can expect most functions to work.

//

// This code is distributed under the GNU Public License

// which can be found at http://www.gnu.org/licenses/gpl.txt

//

//*****************************************************************************

#ifndef WIN32

#include <avr/io.h>

#include <avr/interrupt.h>

#include <avr/pgmspace.h>

#endif

#include <string.h>

#include <stdlib.h>

#include <math.h>

#include "global.h"

#include "buffer.h"

#include "rprintf.h"

#include "gps.h"

#include "nmea.h"

// Program ROM constants

// Global variables

extern GpsInfoType GpsInfo;

uint8_t NmeaPacket[NMEA_BUFFERSIZE];

void nmeaInit(void)

{

}

uint8_t* nmeaGetPacketBuffer(void)

{

return NmeaPacket;

}

uint8_t nmeaProcess(cBuffer* rxBuffer)

{

uint8_t foundpacket = NMEA_NODATA;

uint8_t startFlag = FALSE;

//uint8_t data;

uint16_t i,j;

// process the receive buffer

// go through buffer looking for packets

while(rxBuffer->datalength)

{

// look for a start of NMEA packet

if(bufferGetAtIndex(rxBuffer,0) == '$')

{

// found start

startFlag = TRUE;

// when start is found, we leave it intact in the receive buffer

// in case the full NMEA string is not completely received. The

// start will be detected in the next nmeaProcess iteration.

// done looking for start

break;

}

else

bufferGetFromFront(rxBuffer);

}

// if we detected a start, look for end of packet

if(startFlag)

{

for(i=1; i<(rxBuffer->datalength)-1; i++)

{

// check for end of NMEA packet <CR><LF>

if((bufferGetAtIndex(rxBuffer,i) == '\r') && (bufferGetAtIndex(rxBuffer,i+1) == '\n'))

{

// have a packet end

// dump initial '$'

bufferGetFromFront(rxBuffer);

// copy packet to NmeaPacket

for(j=0; j<(i-1); j++)

{

// although NMEA strings should be 80 characters or less,

// receive buffer errors can generate erroneous packets.

// Protect against packet buffer overflow

if(j<(NMEA_BUFFERSIZE-1))

NmeaPacket[j] = bufferGetFromFront(rxBuffer);

else

bufferGetFromFront(rxBuffer);

}

// null terminate it

NmeaPacket[j] = 0;

// dump <CR><LF> from rxBuffer

bufferGetFromFront(rxBuffer);

bufferGetFromFront(rxBuffer);

#ifdef NMEA_DEBUG_PKT

rprintf("Rx NMEA packet type: ");

rprintfStrLen(NmeaPacket, 0, 5);

rprintfStrLen(NmeaPacket, 5, (i-1)-5);

rprintfCRLF();

#endif

// found a packet

// done with this processing session

foundpacket = NMEA_UNKNOWN;

break;

}

}

}

if(foundpacket)

{

// check message type and process appropriately

if(!strncmp(NmeaPacket, "GPGGA", 5))

{

// process packet of this type

nmeaProcessGPGGA(NmeaPacket);

// report packet type

foundpacket = NMEA_GPGGA;

}

else if(!strncmp(NmeaPacket, "GPVTG", 5))

{

// process packet of this type

nmeaProcessGPVTG(NmeaPacket);

// report packet type

foundpacket = NMEA_GPVTG;

}

}

else if(rxBuffer->datalength >= rxBuffer->size)

{

// if we found no packet, and the buffer is full

// we're logjammed, flush entire buffer

bufferFlush(rxBuffer);

}

return foundpacket;

}

void nmeaProcessGPGGA(uint8_t* packet)

{

uint8_t i;

char* endptr;

double degrees, minutesfrac;

#ifdef NMEA_DEBUG_GGA

rprintf("NMEA: ");

rprintfStr(packet);

rprintfCRLF();

#endif

// start parsing just after "GPGGA,"

i = 6;

// attempt to reject empty packets right away

if(packet[i]==',' && packet[i+1]==',')

return;

// get UTC time [hhmmss.sss]

GpsInfo.PosLLA.TimeOfFix.f = strtod(&packet[i], &endptr);

while(packet[i++] != ','); // next field: latitude

// get latitude [ddmm.mmmmm]

GpsInfo.PosLLA.lat.f = strtod(&packet[i], &endptr);

// convert to pure degrees [dd.dddd] format

minutesfrac = modf(GpsInfo.PosLLA.lat.f/100, &degrees);

GpsInfo.PosLLA.lat.f = degrees + (minutesfrac*100)/60;

// convert to radians

GpsInfo.PosLLA.lat.f *= (M_PI/180);

while(packet[i++] != ','); // next field: N/S indicator

// correct latitute for N/S

if(packet[i] == 'S') GpsInfo.PosLLA.lat.f = -GpsInfo.PosLLA.lat.f;

while(packet[i++] != ','); // next field: longitude

// get longitude [ddmm.mmmmm]

GpsInfo.PosLLA.lon.f = strtod(&packet[i], &endptr);

// convert to pure degrees [dd.dddd] format

minutesfrac = modf(GpsInfo.PosLLA.lon.f/100, &degrees);

GpsInfo.PosLLA.lon.f = degrees + (minutesfrac*100)/60;

// convert to radians

GpsInfo.PosLLA.lon.f *= (M_PI/180);

while(packet[i++] != ','); // next field: E/W indicator

// correct latitute for E/W

if(packet[i] == 'W') GpsInfo.PosLLA.lon.f = -GpsInfo.PosLLA.lon.f;

while(packet[i++] != ','); // next field: position fix status

// position fix status

// 0 = Invalid, 1 = Valid SPS, 2 = Valid DGPS, 3 = Valid PPS

// check for good position fix

if( (packet[i] != '0') && (packet[i] != ',') )

GpsInfo.PosLLA.updates++;

while(packet[i++] != ','); // next field: satellites used

// get number of satellites used in GPS solution

GpsInfo.numSVs = atoi(&packet[i]);

while(packet[i++] != ','); // next field: HDOP (horizontal dilution of precision)

while(packet[i++] != ','); // next field: altitude

// get altitude (in meters)

GpsInfo.PosLLA.alt.f = strtod(&packet[i], &endptr);

while(packet[i++] != ','); // next field: altitude units, always 'M'

while(packet[i++] != ','); // next field: geoid seperation

while(packet[i++] != ','); // next field: seperation units

while(packet[i++] != ','); // next field: DGPS age

while(packet[i++] != ','); // next field: DGPS station ID

while(packet[i++] != '*'); // next field: checksum

}

void nmeaProcessGPVTG(uint8_t* packet)

{

uint8_t i;

char* endptr;

#ifdef NMEA_DEBUG_VTG

rprintf("NMEA: ");

rprintfStr(packet);

rprintfCRLF();

#endif

// start parsing just after "GPVTG,"

i = 6;

// attempt to reject empty packets right away

if(packet[i]==',' && packet[i+1]==',')

return;

// get course (true north ref) in degrees [ddd.dd]

GpsInfo.VelHS.heading.f = strtod(&packet[i], &endptr);

while(packet[i++] != ','); // next field: 'T'

while(packet[i++] != ','); // next field: course (magnetic north)

// get course (magnetic north ref) in degrees [ddd.dd]

//GpsInfo.VelHS.heading.f = strtod(&packet[i], &endptr);

while(packet[i++] != ','); // next field: 'M'

while(packet[i++] != ','); // next field: speed (knots)

// get speed in knots

//GpsInfo.VelHS.speed.f = strtod(&packet[i], &endptr);

while(packet[i++] != ','); // next field: 'N'

while(packet[i++] != ','); // next field: speed (km/h)

// get speed in km/h

GpsInfo.VelHS.speed.f = strtod(&packet[i], &endptr);

while(packet[i++] != ','); // next field: 'K'

while(packet[i++] != '*'); // next field: checksum

GpsInfo.VelHS.updates++;

}