LibrePilot/flight/modules/GPS/UBX.c

/**
 ******************************************************************************
 * @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 "inc\UBX.h"
#include "inc\GPS.h"

// If a PVT sentence is received in the last UBX_PVT_TIMEOUT (ms) timeframe it disables VELNED/POSLLH/SOL/TIMEUTC
#define UBX_PVT_TIMEOUT (1000)
// 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;
        }
    }
}

void parse_ubx_nav_pvt(struct UBX_NAV_PVT *pvt, GPSPositionSensorData *GpsPosition)
{
    GPSVelocitySensorData GpsVelocity;

    check_msgtracker(pvt->iTOW, (ALL_RECEIVED));

    GpsVelocity.North = (float)pvt->velN * 0.001f;
    GpsVelocity.East  = (float)pvt->velE * 0.001f;
    GpsVelocity.Down  = (float)pvt->velD * 0.001f;
    GPSVelocitySensorSet(&GpsVelocity);

    GpsPosition->Groundspeed     = (float)pvt->gSpeed * 0.001f;
    GpsPosition->Heading         = (float)pvt->heading * 1.0e-5f;
    GpsPosition->Altitude        = (float)pvt->hMSL * 0.001f;
    GpsPosition->GeoidSeparation = (float)(pvt->height - pvt->hMSL) * 0.001f;
    GpsPosition->Latitude        = pvt->lat;
    GpsPosition->Longitude       = pvt->lon;
    GpsPosition->Satellites      = pvt->numSV;
    GpsPosition->PDOP = pvt->pDOP * 0.01f;
    if (pvt->flags & PVT_FLAGS_GNSSFIX_OK) {
        GpsPosition->Status = pvt->fixType == PVT_FIX_TYPE_3D ?
                              GPSPOSITIONSENSOR_STATUS_FIX3D : GPSPOSITIONSENSOR_STATUS_FIX2D;
    } else {
        GpsPosition->Status = GPSPOSITIONSENSOR_STATUS_NOFIX;
    }
#if !defined(PIOS_GPS_MINIMAL)
    if (pvt->valid & PVT_VALID_VALIDTIME) {
        // Time is valid, set GpsTime
        GPSTimeData GpsTime;

        GpsTime.Year   = pvt->year;
        GpsTime.Month  = pvt->month;
        GpsTime.Day    = pvt->day;
        GpsTime.Hour   = pvt->hour;
        GpsTime.Minute = pvt->min;
        GpsTime.Second = pvt->sec;

        GPSTimeSet(&GpsTime);
    }
#endif
}
#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;
    static uint32_t lastPvtTime;
    static bool ubxInitialized = false;

    if (!ubxInitialized) {
        // initialize dop values. If no DOP sentence is received it is safer to initialize them to a high value rather than 0.
        GpsPosition->HDOP = 99.99f;
        GpsPosition->PDOP = 99.99f;
        GpsPosition->VDOP = 99.99f;
        ubxInitialized    = true;
    }
    // is it using PVT?
    bool usePvt = (PIOS_DELAY_GetuSSince(lastPvtTime) < UBX_PVT_TIMEOUT * 1000);

    switch (ubx->header.class) {
    case UBX_CLASS_NAV:
        if (!usePvt) {
            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;
            case UBX_ID_PVT:
                parse_ubx_nav_pvt(&ubx->payload.nav_pvt, GpsPosition);
                lastPvtTime = PIOS_DELAY_GetuS();
                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
            }
        } else {
            switch (ubx->header.id) {
            case UBX_ID_DOP:
                parse_ubx_nav_dop(&ubx->payload.nav_dop, GpsPosition);
                break;

            case UBX_ID_PVT:
                parse_ubx_nav_pvt(&ubx->payload.nav_pvt, GpsPosition);
                lastPvtTime = PIOS_DELAY_GetuS();
                break;
#if !defined(PIOS_GPS_MINIMAL)
            case UBX_ID_SVINFO:
                parse_ubx_nav_svinfo(&ubx->payload.nav_svinfo);
                break;
#endif
            default:
                break;
            }
        }
        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