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LibrePilot/flight/modules/GPS/UBX.c

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/**
******************************************************************************
* @addtogroup OpenPilotModules OpenPilot Modules
* @{
* @addtogroup GSPModule GPS Module
* @brief Process GPS information (UBX binary format)
* @{
*
* @file UBX.c
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2012.
* @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"
#if defined(PIOS_INCLUDE_GPS_UBX_PARSER)
#include "UBX.h"
#include "GPS.h"
// parse incoming character stream for messages in UBX binary format
int parse_ubx_stream(uint8_t c, char *gps_rx_buffer, GPSPositionSensorData *GpsData, struct GPS_RX_STATS *gpsRxStats)
{
enum proto_states {
START,
UBX_SY2,
UBX_CLASS,
UBX_ID,
UBX_LEN1,
UBX_LEN2,
UBX_PAYLOAD,
UBX_CHK1,
UBX_CHK2,
FINISHED
};
static enum proto_states proto_state = START;
static uint8_t rx_count = 0;
struct UBXPacket *ubx = (struct UBXPacket *)gps_rx_buffer;
switch (proto_state) {
case START: // detect protocol
if (c == UBX_SYNC1) { // first UBX sync char found
proto_state = UBX_SY2;
}
break;
case UBX_SY2:
if (c == UBX_SYNC2) { // second UBX sync char found
proto_state = UBX_CLASS;
} else {
proto_state = START; // reset state
}
break;
case UBX_CLASS:
ubx->header.class = c;
proto_state = UBX_ID;
break;
case UBX_ID:
ubx->header.id = c;
proto_state = UBX_LEN1;
break;
case UBX_LEN1:
ubx->header.len = c;
proto_state = UBX_LEN2;
break;
case UBX_LEN2:
ubx->header.len += (c << 8);
if (ubx->header.len > sizeof(UBXPayload)) {
gpsRxStats->gpsRxOverflow++;
proto_state = START;
} else {
rx_count = 0;
proto_state = UBX_PAYLOAD;
}
break;
case UBX_PAYLOAD:
if (rx_count < ubx->header.len) {
ubx->payload.payload[rx_count] = c;
if (++rx_count == ubx->header.len) {
proto_state = UBX_CHK1;
}
} else {
gpsRxStats->gpsRxOverflow++;
proto_state = START;
}
break;
case UBX_CHK1:
ubx->header.ck_a = c;
proto_state = UBX_CHK2;
break;
case UBX_CHK2:
ubx->header.ck_b = c;
if (checksum_ubx_message(ubx)) { // message complete and valid
parse_ubx_message(ubx, GpsData);
proto_state = FINISHED;
} else {
gpsRxStats->gpsRxChkSumError++;
proto_state = START;
}
break;
default: break;
}
if (proto_state == START) {
return PARSER_ERROR; // parser couldn't use this byte
} else if (proto_state == FINISHED) {
gpsRxStats->gpsRxReceived++;
proto_state = START;
return PARSER_COMPLETE; // message complete & processed
}
return PARSER_INCOMPLETE; // message not (yet) complete
}
// Keep track of various GPS messages needed to make up a single UAVO update
// time-of-week timestamp is used to correlate matching messages
#define POSLLH_RECEIVED (1 << 0)
#define STATUS_RECEIVED (1 << 1)
#define DOP_RECEIVED (1 << 2)
#define VELNED_RECEIVED (1 << 3)
#define SOL_RECEIVED (1 << 4)
#define ALL_RECEIVED (SOL_RECEIVED | VELNED_RECEIVED | DOP_RECEIVED | POSLLH_RECEIVED)
#define NONE_RECEIVED 0
static struct msgtracker {
uint32_t currentTOW; // TOW of the message set currently in progress
uint8_t msg_received; // keep track of received message types
} msgtracker;
// Check if a message belongs to the current data set and register it as 'received'
bool check_msgtracker(uint32_t tow, uint8_t msg_flag)
{
if (tow > msgtracker.currentTOW ? true // start of a new message set
: (msgtracker.currentTOW - tow > 6 * 24 * 3600 * 1000)) { // 6 days, TOW wrap around occured
msgtracker.currentTOW = tow;
msgtracker.msg_received = NONE_RECEIVED;
} else if (tow < msgtracker.currentTOW) { // message outdated (don't process)
return false;
}
msgtracker.msg_received |= msg_flag; // register reception of this msg type
return true;
}
bool checksum_ubx_message(struct UBXPacket *ubx)
{
int i;
uint8_t ck_a, ck_b;
ck_a = ubx->header.class;
ck_b = ck_a;
ck_a += ubx->header.id;
ck_b += ck_a;
ck_a += ubx->header.len & 0xff;
ck_b += ck_a;
ck_a += ubx->header.len >> 8;
ck_b += ck_a;
for (i = 0; i < ubx->header.len; i++) {
ck_a += ubx->payload.payload[i];
ck_b += ck_a;
}
if (ubx->header.ck_a == ck_a &&
ubx->header.ck_b == ck_b) {
return true;
} else {
return false;
}
}
void parse_ubx_nav_posllh(struct UBX_NAV_POSLLH *posllh, GPSPositionSensorData *GpsPosition)
{
if (check_msgtracker(posllh->iTOW, POSLLH_RECEIVED)) {
if (GpsPosition->Status != GPSPOSITIONSENSOR_STATUS_NOFIX) {
GpsPosition->Altitude = (float)posllh->hMSL * 0.001f;
GpsPosition->GeoidSeparation = (float)(posllh->height - posllh->hMSL) * 0.001f;
GpsPosition->Latitude = posllh->lat;
GpsPosition->Longitude = posllh->lon;
}
}
}
void parse_ubx_nav_sol(struct UBX_NAV_SOL *sol, GPSPositionSensorData *GpsPosition)
{
if (check_msgtracker(sol->iTOW, SOL_RECEIVED)) {
GpsPosition->Satellites = sol->numSV;
if (sol->flags & STATUS_FLAGS_GPSFIX_OK) {
switch (sol->gpsFix) {
case STATUS_GPSFIX_2DFIX:
GpsPosition->Status = GPSPOSITIONSENSOR_STATUS_FIX2D;
break;
case STATUS_GPSFIX_3DFIX:
GpsPosition->Status = GPSPOSITIONSENSOR_STATUS_FIX3D;
break;
default: GpsPosition->Status = GPSPOSITIONSENSOR_STATUS_NOFIX;
}
} else { // fix is not valid so we make sure to treat is as NOFIX
GpsPosition->Status = GPSPOSITIONSENSOR_STATUS_NOFIX;
}
}
}
void parse_ubx_nav_dop(struct UBX_NAV_DOP *dop, GPSPositionSensorData *GpsPosition)
{
if (check_msgtracker(dop->iTOW, DOP_RECEIVED)) {
GpsPosition->HDOP = (float)dop->hDOP * 0.01f;
GpsPosition->VDOP = (float)dop->vDOP * 0.01f;
GpsPosition->PDOP = (float)dop->pDOP * 0.01f;
}
}
void parse_ubx_nav_velned(struct UBX_NAV_VELNED *velned, GPSPositionSensorData *GpsPosition)
{
GPSVelocitySensorData GpsVelocity;
if (check_msgtracker(velned->iTOW, VELNED_RECEIVED)) {
if (GpsPosition->Status != GPSPOSITIONSENSOR_STATUS_NOFIX) {
GpsVelocity.North = (float)velned->velN / 100.0f;
GpsVelocity.East = (float)velned->velE / 100.0f;
GpsVelocity.Down = (float)velned->velD / 100.0f;
GPSVelocitySensorSet(&GpsVelocity);
GpsPosition->Groundspeed = (float)velned->gSpeed * 0.01f;
GpsPosition->Heading = (float)velned->heading * 1.0e-5f;
}
}
}
#if !defined(PIOS_GPS_MINIMAL)
void parse_ubx_nav_timeutc(struct UBX_NAV_TIMEUTC *timeutc)
{
// Test if time is valid
if ((timeutc->valid & TIMEUTC_VALIDTOW) && (timeutc->valid & TIMEUTC_VALIDWKN)) {
// Time is valid, set GpsTime
GPSTimeData GpsTime;
GpsTime.Year = timeutc->year;
GpsTime.Month = timeutc->month;
GpsTime.Day = timeutc->day;
GpsTime.Hour = timeutc->hour;
GpsTime.Minute = timeutc->min;
GpsTime.Second = timeutc->sec;
GPSTimeSet(&GpsTime);
} else {
// Time is not valid, nothing to do
return;
}
}
#endif /* if !defined(PIOS_GPS_MINIMAL) */
#if !defined(PIOS_GPS_MINIMAL)
void parse_ubx_nav_svinfo(struct UBX_NAV_SVINFO *svinfo)
{
uint8_t chan;
GPSSatellitesData svdata;
svdata.SatsInView = 0;
for (chan = 0; chan < svinfo->numCh; chan++) {
if (svdata.SatsInView < GPSSATELLITES_PRN_NUMELEM) {
svdata.Azimuth[svdata.SatsInView] = (float)svinfo->sv[chan].azim;
svdata.Elevation[svdata.SatsInView] = (float)svinfo->sv[chan].elev;
svdata.PRN[svdata.SatsInView] = svinfo->sv[chan].svid;
svdata.SNR[svdata.SatsInView] = svinfo->sv[chan].cno;
svdata.SatsInView++;
}
}
// fill remaining slots (if any)
for (chan = svdata.SatsInView; chan < GPSSATELLITES_PRN_NUMELEM; chan++) {
svdata.Azimuth[chan] = (float)0.0f;
svdata.Elevation[chan] = (float)0.0f;
svdata.PRN[chan] = 0;
svdata.SNR[chan] = 0;
}
GPSSatellitesSet(&svdata);
}
#endif /* if !defined(PIOS_GPS_MINIMAL) */
// UBX message parser
// returns UAVObjectID if a UAVObject structure is ready for further processing
uint32_t parse_ubx_message(struct UBXPacket *ubx, GPSPositionSensorData *GpsPosition)
{
uint32_t id = 0;
switch (ubx->header.class) {
case UBX_CLASS_NAV:
switch (ubx->header.id) {
case UBX_ID_POSLLH:
parse_ubx_nav_posllh(&ubx->payload.nav_posllh, GpsPosition);
break;
case UBX_ID_DOP:
parse_ubx_nav_dop(&ubx->payload.nav_dop, GpsPosition);
break;
case UBX_ID_SOL:
parse_ubx_nav_sol(&ubx->payload.nav_sol, GpsPosition);
break;
case UBX_ID_VELNED:
parse_ubx_nav_velned(&ubx->payload.nav_velned, GpsPosition);
break;
#if !defined(PIOS_GPS_MINIMAL)
case UBX_ID_TIMEUTC:
parse_ubx_nav_timeutc(&ubx->payload.nav_timeutc);
break;
case UBX_ID_SVINFO:
parse_ubx_nav_svinfo(&ubx->payload.nav_svinfo);
break;
#endif
}
break;
}
if (msgtracker.msg_received == ALL_RECEIVED) {
GPSPositionSensorSet(GpsPosition);
msgtracker.msg_received = NONE_RECEIVED;
id = GPSPOSITIONSENSOR_OBJID;
}
return id;
}
#endif // PIOS_INCLUDE_GPS_UBX_PARSER
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