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261 lines
7.4 KiB
C
Executable File
261 lines
7.4 KiB
C
Executable File
/*! \file nmea.c \brief NMEA protocol function library. */
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//*****************************************************************************
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//
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// File Name : 'nmea.c'
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// Title : NMEA protocol function library
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// Author : Pascal Stang - Copyright (C) 2002
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// Created : 2002.08.27
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// Revised : 2002.08.27
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// Version : 0.1
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// Target MCU : Atmel AVR Series
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// Editor Tabs : 4
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//
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// NOTE: This code is currently below version 1.0, and therefore is considered
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// to be lacking in some functionality or documentation, or may not be fully
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// tested. Nonetheless, you can expect most functions to work.
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//
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// This code is distributed under the GNU Public License
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// which can be found at http://www.gnu.org/licenses/gpl.txt
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//
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//*****************************************************************************
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#ifndef WIN32
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#include <avr/io.h>
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#include <avr/signal.h>
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#include <avr/interrupt.h>
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#include <avr/pgmspace.h>
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#endif
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#include <string.h>
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#include <stdlib.h>
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#include <math.h>
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#include "global.h"
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#include "buffer.h"
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#include "rprintf.h"
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#include "gps.h"
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#include "nmea.h"
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// Program ROM constants
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// Global variables
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extern GpsInfoType GpsInfo;
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u08 NmeaPacket[NMEA_BUFFERSIZE];
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void nmeaInit(void)
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{
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}
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u08* nmeaGetPacketBuffer(void)
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{
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return NmeaPacket;
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}
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u08 nmeaProcess(cBuffer* rxBuffer)
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{
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u08 foundpacket = NMEA_NODATA;
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u08 startFlag = FALSE;
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//u08 data;
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u16 i,j;
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// process the receive buffer
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// go through buffer looking for packets
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while(rxBuffer->datalength)
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{
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// look for a start of NMEA packet
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if(bufferGetAtIndex(rxBuffer,0) == '$')
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{
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// found start
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startFlag = TRUE;
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// when start is found, we leave it intact in the receive buffer
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// in case the full NMEA string is not completely received. The
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// start will be detected in the next nmeaProcess iteration.
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// done looking for start
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break;
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}
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else
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bufferGetFromFront(rxBuffer);
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}
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// if we detected a start, look for end of packet
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if(startFlag)
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{
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for(i=1; i<(rxBuffer->datalength)-1; i++)
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{
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// check for end of NMEA packet <CR><LF>
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if((bufferGetAtIndex(rxBuffer,i) == '\r') && (bufferGetAtIndex(rxBuffer,i+1) == '\n'))
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{
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// have a packet end
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// dump initial '$'
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bufferGetFromFront(rxBuffer);
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// copy packet to NmeaPacket
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for(j=0; j<(i-1); j++)
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{
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// although NMEA strings should be 80 characters or less,
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// receive buffer errors can generate erroneous packets.
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// Protect against packet buffer overflow
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if(j<(NMEA_BUFFERSIZE-1))
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NmeaPacket[j] = bufferGetFromFront(rxBuffer);
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else
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bufferGetFromFront(rxBuffer);
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}
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// null terminate it
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NmeaPacket[j] = 0;
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// dump <CR><LF> from rxBuffer
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bufferGetFromFront(rxBuffer);
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bufferGetFromFront(rxBuffer);
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#ifdef NMEA_DEBUG_PKT
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rprintf("Rx NMEA packet type: ");
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rprintfStrLen(NmeaPacket, 0, 5);
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rprintfStrLen(NmeaPacket, 5, (i-1)-5);
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rprintfCRLF();
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#endif
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// found a packet
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// done with this processing session
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foundpacket = NMEA_UNKNOWN;
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break;
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}
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}
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}
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if(foundpacket)
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{
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// check message type and process appropriately
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if(!strncmp(NmeaPacket, "GPGGA", 5))
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{
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// process packet of this type
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nmeaProcessGPGGA(NmeaPacket);
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// report packet type
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foundpacket = NMEA_GPGGA;
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}
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else if(!strncmp(NmeaPacket, "GPVTG", 5))
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{
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// process packet of this type
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nmeaProcessGPVTG(NmeaPacket);
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// report packet type
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foundpacket = NMEA_GPVTG;
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}
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}
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else if(rxBuffer->datalength >= rxBuffer->size)
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{
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// if we found no packet, and the buffer is full
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// we're logjammed, flush entire buffer
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bufferFlush(rxBuffer);
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}
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return foundpacket;
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}
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void nmeaProcessGPGGA(u08* packet)
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{
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u08 i;
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char* endptr;
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double degrees, minutesfrac;
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#ifdef NMEA_DEBUG_GGA
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rprintf("NMEA: ");
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rprintfStr(packet);
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rprintfCRLF();
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#endif
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// start parsing just after "GPGGA,"
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i = 6;
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// attempt to reject empty packets right away
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if(packet[i]==',' && packet[i+1]==',')
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return;
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// get UTC time [hhmmss.sss]
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GpsInfo.PosLLA.TimeOfFix.f = strtod(&packet[i], &endptr);
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while(packet[i++] != ','); // next field: latitude
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// get latitude [ddmm.mmmmm]
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GpsInfo.PosLLA.lat.f = strtod(&packet[i], &endptr);
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// convert to pure degrees [dd.dddd] format
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minutesfrac = modf(GpsInfo.PosLLA.lat.f/100, °rees);
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GpsInfo.PosLLA.lat.f = degrees + (minutesfrac*100)/60;
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// convert to radians
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GpsInfo.PosLLA.lat.f *= (M_PI/180);
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while(packet[i++] != ','); // next field: N/S indicator
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// correct latitute for N/S
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if(packet[i] == 'S') GpsInfo.PosLLA.lat.f = -GpsInfo.PosLLA.lat.f;
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while(packet[i++] != ','); // next field: longitude
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// get longitude [ddmm.mmmmm]
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GpsInfo.PosLLA.lon.f = strtod(&packet[i], &endptr);
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// convert to pure degrees [dd.dddd] format
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minutesfrac = modf(GpsInfo.PosLLA.lon.f/100, °rees);
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GpsInfo.PosLLA.lon.f = degrees + (minutesfrac*100)/60;
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// convert to radians
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GpsInfo.PosLLA.lon.f *= (M_PI/180);
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while(packet[i++] != ','); // next field: E/W indicator
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// correct latitute for E/W
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if(packet[i] == 'W') GpsInfo.PosLLA.lon.f = -GpsInfo.PosLLA.lon.f;
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while(packet[i++] != ','); // next field: position fix status
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// position fix status
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// 0 = Invalid, 1 = Valid SPS, 2 = Valid DGPS, 3 = Valid PPS
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// check for good position fix
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if( (packet[i] != '0') && (packet[i] != ',') )
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GpsInfo.PosLLA.updates++;
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while(packet[i++] != ','); // next field: satellites used
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// get number of satellites used in GPS solution
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GpsInfo.numSVs = atoi(&packet[i]);
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while(packet[i++] != ','); // next field: HDOP (horizontal dilution of precision)
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while(packet[i++] != ','); // next field: altitude
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// get altitude (in meters)
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GpsInfo.PosLLA.alt.f = strtod(&packet[i], &endptr);
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while(packet[i++] != ','); // next field: altitude units, always 'M'
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while(packet[i++] != ','); // next field: geoid seperation
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while(packet[i++] != ','); // next field: seperation units
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while(packet[i++] != ','); // next field: DGPS age
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while(packet[i++] != ','); // next field: DGPS station ID
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while(packet[i++] != '*'); // next field: checksum
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}
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void nmeaProcessGPVTG(u08* packet)
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{
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u08 i;
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char* endptr;
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#ifdef NMEA_DEBUG_VTG
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rprintf("NMEA: ");
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rprintfStr(packet);
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rprintfCRLF();
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#endif
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// start parsing just after "GPVTG,"
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i = 6;
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// attempt to reject empty packets right away
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if(packet[i]==',' && packet[i+1]==',')
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return;
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// get course (true north ref) in degrees [ddd.dd]
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GpsInfo.VelHS.heading.f = strtod(&packet[i], &endptr);
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while(packet[i++] != ','); // next field: 'T'
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while(packet[i++] != ','); // next field: course (magnetic north)
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// get course (magnetic north ref) in degrees [ddd.dd]
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//GpsInfo.VelHS.heading.f = strtod(&packet[i], &endptr);
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while(packet[i++] != ','); // next field: 'M'
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while(packet[i++] != ','); // next field: speed (knots)
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// get speed in knots
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//GpsInfo.VelHS.speed.f = strtod(&packet[i], &endptr);
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while(packet[i++] != ','); // next field: 'N'
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while(packet[i++] != ','); // next field: speed (km/h)
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// get speed in km/h
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GpsInfo.VelHS.speed.f = strtod(&packet[i], &endptr);
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while(packet[i++] != ','); // next field: 'K'
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while(packet[i++] != '*'); // next field: checksum
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GpsInfo.VelHS.updates++;
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}
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