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LibrePilot/flight/Modules/GPS/NMEA.c

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/**
******************************************************************************
* @addtogroup OpenPilotModules OpenPilot Modules
* @{
* @addtogroup GSPModule GPS Module
* @brief Process GPS information
* @{
*
* @file NMEA.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 "pios.h"
#include "gpsposition.h"
#include "NMEA.h"
#include "gpstime.h"
#include "gpssatellites.h"
//#define ENABLE_DEBUG_MSG ///< define to enable debug-messages
#define DEBUG_PORT PIOS_COM_TELEM_RF ///< defines which serial port is ued for debug-messages
// Debugging
#ifdef ENABLE_DEBUG_MSG
//#define DEBUG_MSG_IN ///< define to display the incoming NMEA messages
//#define DEBUG_PARS ///< define to display the incoming NMEA messages split into its parameters
//#define DEBUG_MGSID_IN ///< define to display the the names of the incoming NMEA messages
//#define NMEA_DEBUG_PKT ///< define to enable debug of all NMEA messages
//#define NMEA_DEBUG_GGA ///< define to enable debug of GGA messages
//#define NMEA_DEBUG_VTG ///< define to enable debug of VTG messages
//#define NMEA_DEBUG_RMC ///< define to enable debug of RMC messages
//#define NMEA_DEBUG_GSA ///< define to enable debug of GSA messages
//#define NMEA_DEBUG_GSV ///< define to enable debug of GSV messages
//#define NMEA_DEBUG_ZDA ///< define to enable debug of ZDA messages
#define DEBUG_MSG(format, ...) PIOS_COM_SendFormattedString(DEBUG_PORT, format, ## __VA_ARGS__)
#else
#define DEBUG_MSG(format, ...)
#endif
#define MAX_NB_PARAMS 20
#define NMEA_DOP_NOFIX 99.99
/* NMEA sentence parsers */
struct nmea_parser {
const char *prefix;
bool(*handler) (GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam);
uint32_t cnt;
};
static bool nmeaProcessGPGGA(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam);
static bool nmeaProcessGPRMC(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam);
static bool nmeaProcessGPVTG(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam);
static bool nmeaProcessGPGSA(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam);
#if !defined(PIOS_GPS_MINIMAL)
static bool nmeaProcessGPZDA(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam);
static bool nmeaProcessGPGSV(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam);
#endif //PIOS_GPS_MINIMAL
static struct nmea_parser nmea_parsers[] = {
{
.prefix = "GPGGA",
.handler = nmeaProcessGPGGA,
.cnt = 0,
},
{
.prefix = "GPVTG",
.handler = nmeaProcessGPVTG,
.cnt = 0,
},
{
.prefix = "GPGSA",
.handler = nmeaProcessGPGSA,
.cnt = 0,
},
{
.prefix = "GPRMC",
.handler = nmeaProcessGPRMC,
.cnt = 0,
},
#if !defined(PIOS_GPS_MINIMAL)
{
.prefix = "GPZDA",
.handler = nmeaProcessGPZDA,
.cnt = 0,
},
{
.prefix = "GPGSV",
.handler = nmeaProcessGPGSV,
.cnt = 0,
},
#endif //PIOS_GPS_MINIMAL
};
static struct nmea_parser *NMEA_find_parser_by_prefix(const char *prefix)
{
if (!prefix) {
return (NULL);
}
for (uint8_t i = 0; i < NELEMENTS(nmea_parsers); i++) {
struct nmea_parser *parser = &nmea_parsers[i];
/* Use strcmp to check for exact equality over the entire prefix */
if (!strcmp(prefix, parser->prefix)) {
/* Found an appropriate parser */
return (parser);
}
}
/* No matching parser for this prefix */
return (NULL);
}
/**
* Computes NMEA sentence checksum
* \param[in] Buffer for parsed nmea sentence
* \return false checksum not valid
* \return true checksum valid
*/
bool NMEA_checksum(char *nmea_sentence)
{
uint8_t checksum_computed = 0;
uint8_t checksum_received;
while (*nmea_sentence != '\0' && *nmea_sentence != '*') {
checksum_computed ^= *nmea_sentence;
nmea_sentence++;
}
/* Make sure we're now pointing at the checksum */
if (*nmea_sentence == '\0') {
/* Buffer ran out before we found a checksum marker */
return false;
}
/* Load the checksum from the buffer */
checksum_received = strtol(nmea_sentence + 1, NULL, 16);
//PIOS_COM_SendFormattedStringNonBlocking(COM_DEBUG_USART,"$%d=%d\r\n",checksum_received,checksum_computed);
return (checksum_computed == checksum_received);
}
/*
* This function only exists to deal with a linking
* failure in the stdlib function strtof(). This
* implementation does not rely on the _sbrk() syscall
* like strtof() does.
*/
/* Parse a number encoded in a string of the format:
* [-]NN.nnnnn
* into a signed whole part and an unsigned fractional part.
* The fract_units field indicates the units of the fractional part as
* 1 whole = 10^fract_units fract
*/
static bool NMEA_parse_real(int32_t * whole, uint32_t * fract, uint8_t * fract_units, char *field)
{
char *s = field;
char *field_w;
char *field_f;
PIOS_DEBUG_Assert(whole);
PIOS_DEBUG_Assert(fract);
PIOS_DEBUG_Assert(fract_units);
field_w = strsep(&s, ".");
field_f = s;
*whole = strtol(field_w, NULL, 10);
if (field_w) {
/* decimal was found so we may have a fractional part */
*fract = strtoul(field_f, NULL, 10);
*fract_units = strlen(field_f);
} else {
/* no decimal was found, fractional part is zero */
*fract = 0;
*fract_units = 0;
}
return true;
}
static float NMEA_real_to_float(char *nmea_real)
{
int32_t whole;
uint32_t fract;
uint8_t fract_units;
/* Sanity checks */
PIOS_DEBUG_Assert(nmea_real);
if (!NMEA_parse_real(&whole, &fract, &fract_units, nmea_real)) {
return false;
}
/* Convert to float */
return (((float)whole) + fract * powf(10.0f, -fract_units));
}
/*
* Parse a field in the format:
* DD[D]MM.mmmm[mm]
* into a fixed-point representation in units of (degrees * 1e-7)
*/
static bool NMEA_latlon_to_fixed_point(int32_t * latlon, char *nmea_latlon, bool negative)
{
int32_t num_DDDMM;
uint32_t num_m;
uint8_t units;
/* Sanity checks */
PIOS_DEBUG_Assert(nmea_latlon);
PIOS_DEBUG_Assert(latlon);
if (*nmea_latlon == '\0') { /* empty lat/lon field */
return false;
}
if (!NMEA_parse_real(&num_DDDMM, &num_m, &units, nmea_latlon)) {
return false;
}
/* scale up the mmmm[mm] field apropriately depending on # of digits */
/* not using 1eN notation because that forces fixed point and lost precision */
switch (units) {
case 0:
/* no digits, value is zero so no scaling */
break;
case 1: /* m */
num_m *= 1000000; /* m000000 */
break;
case 2: /* mm */
num_m *= 100000; /* mm00000 */
break;
case 3: /* mmm */
num_m *= 10000; /* mmm0000 */
break;
case 4: /* mmmm */
num_m *= 1000; /* mmmm000 */
break;
case 5: /* mmmmm */
num_m *= 100; /* mmmmm00 */
break;
case 6: /* mmmmmm */
num_m *= 10; /* mmmmmm0 */
break;
default:
/* unhandled format */
num_m = 0.0f;
break;
}
*latlon = (num_DDDMM / 100) * 10000000; /* scale the whole degrees */
*latlon += (num_DDDMM % 100) * 10000000 / 60; /* add in the scaled decimal whole minutes */
*latlon += num_m / 60; /* add in the scaled decimal fractional minutes */
if (negative)
*latlon *= -1;
return true;
}
/**
* Parses a complete NMEA sentence and updates the GPSPosition UAVObject
* \param[in] An NMEA sentence with a valid checksum
* \return true if the sentence was successfully parsed
* \return false if any errors were encountered with the parsing
*/
bool NMEA_update_position(char *nmea_sentence, GPSPositionData *GpsData)
{
char* p = nmea_sentence;
char* params[MAX_NB_PARAMS];
uint8_t nbParams;
#ifdef DEBUG_MSG_IN
DEBUG_MSG("\"%s\"\n", nmea_sentence);
#endif
// Split the nmea sentence it its parameters, separated by ","
// Sample NMEA message: "GPRMC,000131.736,V,,,,,0.00,0.00,060180,,,N*43"
// The first parameter starts at the beginning of the message
params[0] = p;
nbParams = 1;
while (*p != 0) {
if (*p == '*') {
// After the * comes the "CRC", we are done,
*p = 0; // Zero-terminate this parameter
break;
} else if (*p == ',') {
// This is the end of this parameter
*p = 0; // Zero-terminate this parameter
// Start new parameter
if (nbParams==MAX_NB_PARAMS)
break;
params[nbParams] = p+1; // For sure there is something at p+1 because at p there is ","
nbParams++;
}
p++;
}
#ifdef DEBUG_PARAMS
int i;
for (i=0;i<nbParams; i++) {
DEBUG_MSG(" %d \"%s\"\n", i, params[i]);
}
#endif
// The first parameter is the message name, lets see if we find a parser for it
struct nmea_parser *parser;
parser = NMEA_find_parser_by_prefix(params[0]);
if (!parser) {
// No parser found
DEBUG_MSG(" NO PARSER (\"%s\")\n", params[0]);
return false;
}
parser->cnt++;
#ifdef DEBUG_MGSID_IN
DEBUG_MSG("%s %d ", params[0], parser->cnt);
#endif
// Send the message to the parser and get it update the GpsData
bool gpsDataUpdated = false;
if (!parser->handler(GpsData, &gpsDataUpdated, params, nbParams)) {
// Parse failed
DEBUG_MSG("PARSE FAILED (\"%s\")\n", params[0]);
return false;
}
// All is fine :) Update object if data has changed
if (gpsDataUpdated) {
#ifdef DEBUG_MGSID_IN
DEBUG_MSG("U");
#endif
GPSPositionSet(GpsData);
}
#ifdef DEBUG_MGSID_IN
DEBUG_MSG("\n");
#endif
return true;
}
/**
* Parse an NMEA GPGGA sentence and update the given UAVObject
* \param[in] A pointer to a GPSPosition UAVObject to be updated.
* \param[in] An NMEA sentence with a valid checksum
*/
static bool nmeaProcessGPGGA(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam)
{
if (nbParam != 15)
return false;
#ifdef NMEA_DEBUG_GGA
DEBUG_MSG("\n UTC=%s\n", param[1]);
DEBUG_MSG(" Lat=%s %s\n", param[2], param[3]);
DEBUG_MSG(" Long=%s %s\n", param[4], param[5]);
DEBUG_MSG(" Fix=%s\n", param[6]);
DEBUG_MSG(" Sat=%s\n", param[7]);
DEBUG_MSG(" HDOP=%s\n", param[8]);
DEBUG_MSG(" Alt=%s %s\n", param[9], param[10]);
DEBUG_MSG(" GeoidSep=%s %s\n\n", param[11]);
#endif
*gpsDataUpdated = true;
// get latitude [DDMM.mmmmm] [N|S]
if (!NMEA_latlon_to_fixed_point(&GpsData->Latitude, param[2], param[3][0] == 'S') ||
// get longitude [dddmm.mmmmm] [E|W]
!NMEA_latlon_to_fixed_point(&GpsData->Longitude, param[4], param[5][0] == 'W') ||
// check for invalid GPS fix
param[6][0] == '0') {
GpsData->Status = GPSPOSITION_STATUS_NOFIX;
GpsData->PDOP = GpsData->HDOP = GpsData->VDOP = NMEA_DOP_NOFIX;
}
// get number of satellites used in GPS solution
GpsData->Satellites = atoi(param[7]);
// get altitude (in meters mm.m)
GpsData->Altitude = NMEA_real_to_float(param[9]);
// geoid separation
GpsData->GeoidSeparation = NMEA_real_to_float(param[11]);
return true;
}
/**
* Parse an NMEA GPRMC sentence and update the given UAVObject
* \param[in] A pointer to a GPSPosition UAVObject to be updated.
* \param[in] An NMEA sentence with a valid checksum
*/
static bool nmeaProcessGPRMC(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam)
{
if (nbParam != 13)
return false;
#ifdef NMEA_DEBUG_RMC
DEBUG_MSG("\n UTC=%s\n", param[1]);
DEBUG_MSG(" Lat=%s %s\n", param[3], param[4]);
DEBUG_MSG(" Long=%s %s\n", param[5], param[6]);
DEBUG_MSG(" Speed=%s\n", param[7]);
DEBUG_MSG(" Course=%s\n", param[8]);
DEBUG_MSG(" DateOfFix=%s\n\n", param[9]);
#endif
*gpsDataUpdated = false;
#if !defined(PIOS_GPS_MINIMAL)
GPSTimeData gpst;
GPSTimeGet(&gpst);
// get UTC time [hhmmss.sss]
float hms = NMEA_real_to_float(param[1]);
gpst.Second = (int)hms % 100;
gpst.Minute = (((int)hms - gpst.Second) / 100) % 100;
gpst.Hour = (int)hms / 10000;
// get Date of fix
// TODO: Should really not use a float here to be safe
float date = NMEA_real_to_float(param[9]);
gpst.Year = (int)date % 100;
gpst.Month = (((int)date - gpst.Year) / 100) % 100;
gpst.Day = (int)(date / 10000);
gpst.Year += 2000;
GPSTimeSet(&gpst);
#endif //PIOS_GPS_MINIMAL
// don't process void sentences
if (param[2][0] == 'V') {
return false;
}
// get latitude [DDMM.mmmmm] [N|S]
if (!NMEA_latlon_to_fixed_point(&GpsData->Latitude, param[3], param[4][0] == 'S') ||
// get longitude [dddmm.mmmmm] [E|W]
!NMEA_latlon_to_fixed_point(&GpsData->Longitude, param[5], param[6][0] == 'W')) {
GpsData->Status = GPSPOSITION_STATUS_NOFIX;
GpsData->PDOP = GpsData->HDOP = GpsData->VDOP = NMEA_DOP_NOFIX;
}
// get speed in knots
GpsData->Groundspeed = NMEA_real_to_float(param[7]) * 0.51444f; // to m/s
// get True course
GpsData->Heading = NMEA_real_to_float(param[8]);
return true;
}
/**
* Parse an NMEA GPVTG sentence and update the given UAVObject
* \param[in] A pointer to a GPSPosition UAVObject to be updated.
* \param[in] An NMEA sentence with a valid checksum
*/
static bool nmeaProcessGPVTG(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam)
{
if (nbParam != 9 && nbParam != 10 /*GTOP GPS seems to gemnerate an extra parameter...*/)
return false;
#ifdef NMEA_DEBUG_RMC
DEBUG_MSG("\n Heading=%s %s\n", param[1], param[2]);
DEBUG_MSG(" GroundSpeed=%s %s\n", param[5], param[6]);
#endif
*gpsDataUpdated = false;
GpsData->Heading = NMEA_real_to_float(param[1]);
GpsData->Groundspeed = NMEA_real_to_float(param[5]) * 0.51444f; // to m/s
return true;
}
#if !defined(PIOS_GPS_MINIMAL)
/**
* Parse an NMEA GPZDA sentence and update the @ref GPSTime object
* \param[in] A pointer to a GPSPosition UAVObject to be updated (unused).
* \param[in] An NMEA sentence with a valid checksum
*/
static bool nmeaProcessGPZDA(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam)
{
if (nbParam != 7)
return false;
#ifdef NMEA_DEBUG_ZDA
DEBUG_MSG("\n Time=%s (hhmmss.ss)\n", param[1]);
DEBUG_MSG(" Date=%s/%s/%s (d/m/y)\n", param[2], param[3], param[4]);
#endif
*gpsDataUpdated = false; // Here we will never provide a new GPS value
// No new data data extracted
GPSTimeData gpst;
GPSTimeGet(&gpst);
// get UTC time [hhmmss.sss]
float hms = NMEA_real_to_float(param[1]);
gpst.Second = (int)hms % 100;
gpst.Minute = (((int)hms - gpst.Second) / 100) % 100;
gpst.Hour = (int)hms / 10000;
// Get Date
gpst.Day = atoi(param[2]);
gpst.Month = atoi(param[3]);
gpst.Year = atoi(param[4]);
GPSTimeSet(&gpst);
return true;
}
static GPSSatellitesData gsv_partial;
/* Bitmaps of which sentences we're looking for to allow us to handle out-of-order GSVs */
static uint8_t gsv_expected_mask;
static uint8_t gsv_processed_mask;
/* Error counters */
static uint16_t gsv_incomplete_error;
static uint16_t gsv_duplicate_error;
static bool nmeaProcessGPGSV(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam)
{
if (nbParam < 4)
return false;
#ifdef NMEA_DEBUG_GSV
DEBUG_MSG("\n Sentence=%s/%s\n", param[2], param[1]);
DEBUG_MSG(" Sats=%s\n", param[3]);
#endif
uint8_t nbSentences = atoi(param[1]);
uint8_t currSentence = atoi(param[2]);
*gpsDataUpdated = false;
if (nbSentences < 1 || nbSentences > 8 || currSentence < 1 || currSentence > nbSentences)
return false;
gsv_partial.SatsInView = atoi(param[3]);
// Find out if this is the first sentence in the GSV set
if (currSentence == 1) {
if (gsv_expected_mask != gsv_processed_mask) {
// We are starting over when we haven't yet finished our previous GSV group
gsv_incomplete_error++;
}
// First GSV sentence in the sequence, reset our expected_mask
gsv_expected_mask = (1 << nbSentences) - 1;
}
uint8_t current_sentence_id = (1 << (currSentence - 1));
if (gsv_processed_mask & current_sentence_id) {
/* Duplicate sentence in this GSV set */
gsv_duplicate_error++;
} else {
/* Note that we've seen this sentence */
gsv_processed_mask |= current_sentence_id;
}
uint8_t parIdx = 4;
#ifdef NMEA_DEBUG_GSV
DEBUG_MSG(" PRN:");
#endif
/* Make sure this sentence can fit in our GPSSatellites object */
if ((currSentence * 4) <= NELEMENTS(gsv_partial.PRN)) {
/* Process 4 blocks of satellite info */
for (uint8_t i = 0; parIdx+4 <= nbParam && i < 4; i++) {
uint8_t sat_index = ((currSentence - 1) * 4) + i;
// Get sat info
gsv_partial.PRN[sat_index] = atoi(param[parIdx++]);
gsv_partial.Elevation[sat_index] = NMEA_real_to_float(param[parIdx++]);
gsv_partial.Azimuth[sat_index] = NMEA_real_to_float(param[parIdx++]);
gsv_partial.SNR[sat_index] = atoi(param[parIdx++]);
#ifdef NMEA_DEBUG_GSV
DEBUG_MSG(" %d", gsv_partial.PRN[sat_index]);
#endif
}
}
#ifdef NMEA_DEBUG_GSV
DEBUG_MSG("\n");
#endif
/* Find out if we're finished processing all GSV sentences in the set */
if ((gsv_expected_mask != 0) && (gsv_processed_mask == gsv_expected_mask)) {
/* GSV set has been fully processed. Update the GPSSatellites object. */
GPSSatellitesSet(&gsv_partial);
memset((void *)&gsv_partial, 0, sizeof(gsv_partial));
gsv_expected_mask = 0;
gsv_processed_mask = 0;
}
return true;
}
#endif //PIOS_GPS_MINIMAL
/**
* Parse an NMEA GPGSA sentence and update the given UAVObject
* \param[in] A pointer to a GPSPosition UAVObject to be updated.
* \param[in] An NMEA sentence with a valid checksum
*/
static bool nmeaProcessGPGSA(GPSPositionData * GpsData, bool* gpsDataUpdated, char* param[], uint8_t nbParam)
{
if (nbParam != 18)
return false;
#ifdef NMEA_DEBUG_GSA
DEBUG_MSG("\n Status=%s\n", param[2]);
DEBUG_MSG(" PDOP=%s\n", param[15]);
DEBUG_MSG(" HDOP=%s\n", param[16]);
DEBUG_MSG(" VDOP=%s\n", param[17]);
#endif
*gpsDataUpdated = false;
switch (atoi(param[2])) {
case 1:
GpsData->Status = GPSPOSITION_STATUS_NOFIX;
break;
case 2:
GpsData->Status = GPSPOSITION_STATUS_FIX2D;
break;
case 3:
GpsData->Status = GPSPOSITION_STATUS_FIX3D;
break;
default:
/* Unhandled */
return false;
break;
}
// next field: PDOP
GpsData->PDOP = NMEA_real_to_float(param[15]);
// next field: HDOP
GpsData->HDOP = NMEA_real_to_float(param[16]);
// next field: VDOP
GpsData->VDOP = NMEA_real_to_float(param[17]);
return true;
}
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