Android Hal layer GPS research summary-Analysis of gps gga/GSV/RMC data

[Turn] Android Hal layer GPS research summary
2011-09-22

A fast run may not win, a competitive battle may not win, a smart one may not win food, or a wise one may not win money, or a flexible one may not be excited. What came to the world was the opportunity.

In my life, if the twilight grass. /Eclair/hardware/libhardware_legacy/include/hardware_legacy/GPS. h

Typedef struct {
? ? /** Contains gpslocationflags bits .*/
? ? Uint16_t? ? ? ? Flags;
? ? /** Represents latitude in degrees .*/
? ? Double? ? ? ? ? Latitude;
? ? /** Represents longpolling in degrees .*/
? ? Double? ? ? ? ? Longpolling;
? ? /** Represents altitude in meters above the WGS 84 reference
? ? ? * Ellipsoid .*/
? ? Double? ? ? ? ? Altitude;
? ? /** Represents speed in meters per second .*/
? ? Float? ? ? ? ? Speed;
? ? /** Represents heading in degrees .*/
? ? Float? ? ? ? ? Bearing;
? ? /** Represents expected accuracy in meters .*/
? ? Float? ? ? ? ? Accuracy;
? ? /** Timestamp for the location fix .*/
? ? Gpsutctime? ? ? Timestamp;
} Gpslocation;

?

Flags is the identifier

# Define gps_location_has_lat_long? 0x0001 ,? When the bit0 value of flags is 1, the ID position information includes the longitude and latitude information.
/** Gpslocation has valid altitude .*/
# Define gps_location_has_altitude? 0x0002. When the bit1 value of flags is 1, the status information of the flag has a height. The following identifiers are similar.
/** Gpslocation has valid speed .*/
# Define gps_location_has_speed? ? ? Zero X 0004
/** Gpslocation has valid bearing .*/
# Define gps_location_has_bearing? ? Zero X 0008
/** Gpslocation has valid accuracy .*/
# Define gps_location_has_accuracy? Zero X 0010

Typedef void (* gps_status_callback) (gpsstatus * status );

You can use this function to submit the identification information.

Timestamp

Is a 64-bit unsigned integer. It defines the number of seconds from 00:00:00 on January 1, January 01, 1970 to the present in UTC. However, in Android Java, the date function must input a millisecond value, but the decimal value is second, so it must be multiplied by 1000.

Bearing

Corresponding to 8th data disconnections (from 0) of RMC. Course over ground)

Typedef struct {
? ? ? ? /** Number of SVS currently visible .*/
? ? ? ? Int? ? ? ? Num_svs;
? ? ? ? /** Contains an array of SV information .*/
? ? ? ? Gpssvinfo? Sv_list [gps_max_svs];
? ? ? ? /** Represents a bit mask indicating which SVS
? ? ? ? ? * Have ephemeris data.
? ? ? ? ? */
? ? ? ? Uint32_t? ? Ephemeris_mask;
? ? ? ? /** Represents a bit mask indicating which SVS
? ? ? ? ? * Have almanac data.
? ? ? ? ? */
? ? ? ? Uint32_t? ? Almanac_mask;
? ? ? ? /**
? ? ? ? ? * Represents a bit mask indicating which SVS
? ? ? ? ? * Were used for computing the most recent position fix.
? ? ? ? ? */
? ? ? ? Uint32_t? ? Used_in_fix_mask;
} Gpssvstatus;

?

Used_in_fix_mask

If you receive the following datagram ￥ gpgsa, A, 2.8, 1.5, 2.3, * 38

? ? ? 07, 19 ,? 08 ?, 03 ?, ? 16, 11 ,? 06 is a valid Satellite Number (PRN)Used_in_fix_mask

Bit? 6 ?, 18 ,? 7? , 2 ?, ? 15 ?, 10 ,? 5? It is 1, and the other bits are 0. (bit0 is also 0)

Ephemeris_mask, almanac_mask

These two masks are closely related to GSV information.

For example, the following information is received. (In order to facilitate data parsing, I have added a new line)

￥ Gpgsv, 3,1, 11,

19,79, 359,30 ,?

, 22,

, 46,

, 40, * 7b

Satellite No. (PRN ),

￥Gpgsv, 3,2, 11,

11,37, 180 ,,

, 29,

16,30, 050,35,

, 27, * 7A

Satellite Number (PRN ),

￥Gpgsv, 3,3, 11,

24, 17, 178 ,,

319,

28, 31, 02,133, * 4C

Satellite No. (PRN) 24, 08, 28

The BIT (, 22,10, 5, 15, 06,? , 07, 27) Is 1, and other bits are 0 (bit starts from 0th bits ),

The value of the mask is closely related to the Satellite Number.

In short, you must have a deep understanding of the data structure of the company.

Post the first code: eclair/hardware/libhardware_legacy/GPS/gps_qemu.c

Welcome to exchange.

<pre name="code" class="cpp">static voidnmea_reader_parse（ NmeaReader* r ）{D（"％s，％d，％s"，__FILE__，__LINE__，__FUNCTION__）;   /* we received a complete sentence， now parse it to generate    * a new GPS fix...    */    NmeaTokenizer tzer[1];    Token tok;   D（"Received: ""％.*s"""， r->pos， r->in）;    if （r->pos < 9） {        D（"Too short. discarded."）;        return;    }    nmea_tokenizer_init（tzer， r->in， r->in + r->pos）;＃if GPS_DEBUG    {        int n;        for （n = 0; n < tzer->count; n++） {            Token tok = nmea_tokenizer_get（tzer，n）;        }    }＃endif    tok = nmea_tokenizer_get（tzer， 0）;    if （tok.p + 5 > tok.end） {        return;    }    /* ignore first two characters.*/    tok.p += 2;    if （ !memcmp（tok.p， "GGA"， 3） ） {        /* GPS fix */D（"may％s，％d，％s，gGA"，__FILE__，__LINE__，__FUNCTION__）;        Token tok_time = nmea_tokenizer_get（tzer，1）;        Token tok_latitude = nmea_tokenizer_get（tzer，2）;        Token tok_latitudeHemi = nmea_tokenizer_get（tzer，3）;        Token tok_longitude = nmea_tokenizer_get（tzer，4）;        Token tok_longitudeHemi = nmea_tokenizer_get（tzer，5）;        Token tok_altitude = nmea_tokenizer_get（tzer，9）;        Token tok_altitudeUnits = nmea_tokenizer_get（tzer，10）;        nmea_reader__time（r， tok_time）;        nmea_reader__latlong（r， tok_latitude，                                      tok_latitudeHemi.p[0]，                                      tok_longitude，                                      tok_longitudeHemi.p[0]）;        nmea_reader__altitude（r， tok_altitude， tok_altitudeUnits）;    }else if （ !memcmp（tok.p， "GLL"， 3） ） {    Token tok_fixstaus = nmea_tokenizer_get（tzer，6）;    if （tok_fixstaus.p[0] == ""A""） {     Token tok_latitude = nmea_tokenizer_get（tzer，1）;     Token tok_latitudeHemi = nmea_tokenizer_get（tzer，2）;     Token tok_longitude = nmea_tokenizer_get（tzer，3）;     Token tok_longitudeHemi = nmea_tokenizer_get（tzer，4）;     Token tok_time = nmea_tokenizer_get（tzer，5）;     nmea_reader__time（r， tok_time）;     nmea_reader__latlong（r， tok_latitude， tok_latitudeHemi.p[0]， tok_longitude， tok_longitudeHemi.p[0]）;    }    }    ＃ifdef Svpnd_Version    else if （ !memcmp（tok.p， "GSV"， 3） ） {D（"may％s，％d，％s，gsV"，__FILE__，__LINE__，__FUNCTION__）;    Token tok_noSatellites = nmea_tokenizer_get（tzer， 3）;    int noSatellites = str2int（tok_noSatellites.p， tok_noSatellites.end）;       D（"％d，inview=％d，"，__LINE__，noSatellites）;      if （noSatellites > 0） {     Token tok_noSentences = nmea_tokenizer_get（tzer， 1）;     Token tok_sentence     = nmea_tokenizer_get（tzer， 2）;         int sentence = str2int（tok_sentence.p， tok_sentence.end）;     int totalSentences = str2int（tok_noSentences.p， tok_noSentences.end）;   D（"％d，gsv_index=％d，gsv_total=％d"，__LINE__，sentence，totalSentences）;       int curr;     int i;                  if （sentence == 1） {D（"msg_index=％d"，sentence）;   //  r->sv_status_changed = 0;     r->sv_status.num_svs = 0;r->sv_status.ephemeris_mask=0ul;r->sv_status.almanac_mask=0ul;     }            curr = r->sv_status.num_svs;           i = 0;            while （i < 4 && r->sv_status.num_svs < noSatellites）{         Token    tok_prn = nmea_tokenizer_get（tzer， i * 4 + 4）;         Token    tok_elevation = nmea_tokenizer_get（tzer， i * 4 + 5）;         Token    tok_azimuth = nmea_tokenizer_get（tzer， i * 4 + 6）;         Token    tok_snr = nmea_tokenizer_get（tzer， i * 4 + 7）;             r->sv_status.sv_list[curr].prn = str2int（tok_prn.p， tok_prn.end）;         r->sv_status.sv_list[curr].elevation = str2float（tok_elevation.p， tok_elevation.end）;         r->sv_status.sv_list[curr].azimuth = str2float（tok_azimuth.p， tok_azimuth.end）;         r->sv_status.sv_list[curr].snr = str2float（tok_snr.p， tok_snr.end）;     r->sv_status.ephemeris_mask|=（1ul << （r->sv_status.sv_list[curr].prn-1））;r->sv_status.almanac_mask|=（1ul << （r->sv_status.sv_list[curr].prn-1））;         r->sv_status.num_svs += 1; D（"**********curr=％d"，curr）;    D（"％d，prn=％d:snr=％f"，__LINE__，r->sv_status.sv_list[curr].prn，r->sv_status.sv_list[curr].snr）;         curr += 1;             i += 1;     }         if （sentence == totalSentences） {D（"msg=％d，msgindex=％d"，totalSentences，sentence）;        ＃ifdef Svpnd_Versionr->callback.sv_status_cb=_gps_state->callbacks.sv_status_cb;     if （r->sv_status_changed !=0） {           if （r->callback.sv_status_cb） {＃if GPS_DEBUGD（"％d，SV_STATSU，change=％d"，__LINE__，r->sv_status_changed）;int nums=r->sv_status.num_svs;D（"num_svs=％d，emask=％x，amask=％x，inusemask=％x"，r->sv_status.num_svs，r->sv_status.ephemeris_mask，r->sv_status.almanac_mask，r->sv_status.used_in_fix_mask）;D（"************88"）;while（nums）{nums--;D（"prn=％d:snr=％f"，r->sv_status.sv_list[nums].prn，r->sv_status.sv_list[nums].snr）;}D（"************88"）;＃endif                 r->callback.sv_status_cb（ &（r->sv_status） ）;               r->sv_status_changed = 0;             }else {                D（"no callback， keeping status data until needed !"）;           }        }     ＃endif     }         D（"％s: GSV message with total satellites ％d"， __FUNCTION__， noSatellites）;         }                 }    ＃endif        else if （ !memcmp（tok.p， "GSA"， 3） ） {    ＃ifdef Svpnd_Version        /* do something ？ */        {D（"may％s，％d，％s，gsa"，__FILE__，__LINE__，__FUNCTION__）;        Token tok_fixStatus = nmea_tokenizer_get（tzer， 2）;        int i;        if （tok_fixStatus.p[0] != """" && tok_fixStatus.p[0] != ""1""） {            Token tok_accuracy = nmea_tokenizer_get（tzer， 15）;//position dilution of precision dop            nmea_reader__accuracy（r， tok_accuracy）;            r->sv_status.used_in_fix_mask = 0ul;D（""）;            for （i = 3; i <= 14; ++i）{                Token tok_prn = nmea_tokenizer_get（tzer， i）;                int prn = str2int（tok_prn.p， tok_prn.end）;D（"gsa，prn=％d，"，prn）;                if （prn > 0）{                    r->sv_status.used_in_fix_mask |= （1ul << （ prn-1））;                    r->sv_status_changed = 1;                                  }           }D（""）; D（"％s: fix mask is ％x"， __FUNCTION__， r->sv_status.used_in_fix_mask）;      //   D（" [log hit][％s:％d] fix.flags=0 x％x "， __FUNCTION__， __LINE__， r->fix.flags）;        }       D（" [log hit][％s:％d] fix.flags=0 x％x "， __FUNCTION__， __LINE__， r->fix.flags）;    }    ＃endif        /* do something ？ */    } else if （ !memcmp（tok.p， "RMC"， 3） ） {        Token tok_time = nmea_tokenizer_get（tzer，1）;        Token tok_fixStatus = nmea_tokenizer_get（tzer，2）;        Token tok_latitude = nmea_tokenizer_get（tzer，3）;        Token tok_latitudeHemi = nmea_tokenizer_get（tzer，4）;        Token tok_longitude = nmea_tokenizer_get（tzer，5）;        Token tok_longitudeHemi = nmea_tokenizer_get（tzer，6）;        Token tok_speed = nmea_tokenizer_get（tzer，7）;        Token tok_bearing = nmea_tokenizer_get（tzer，8）;        Token tok_date = nmea_tokenizer_get（tzer，9）;        D（"in RMC， fixStatus=％c"， tok_fixStatus.p[0]）;       if （tok_fixStatus.p[0] == ""A""）        {            nmea_reader__date（ r， tok_date， tok_time ）;            nmea_reader__latlong（ r， tok_latitude，                                           tok_latitudeHemi.p[0]，                                           tok_longitude，                                           tok_longitudeHemi.p[0] ）;            nmea_reader__bearing（ r， tok_bearing ）;            nmea_reader__speed （ r， tok_speed ）; ＃ifdef Svpnd_Versionr->callback.location_cb=_gps_state->callbacks.location_cb;r->callback.nmea_cb=_gps_state->callbacks.nmea_cb;r->callback.status_cb=_gps_state->callbacks.status_cb;if （r->callback.status_cb） {D（"report，status，flags=％d"，r->fix.flags）;            r->callback.status_cb（ （struct GpsStatus *）&（r->fix.flags） ）;        }     if （r->callback.location_cb） {D（"location_cb report:r->fix.flags=％d，r->latitude=％f，r->longitude=％f，r->altitude=％f，r->speed=％f，r->bearing=％f，r->accuracy=％f"，r->fix.flags，r->fix.latitude，r->fix.longitude，r->fix.altitude，r->fix.speed，r->fix.bearing，r->fix.accuracy）;            r->callback.location_cb（ &r->fix ）;D（"％d，cc=％d"，__LINE__，cc）;r->fix.flags = 0;        }if （r->callback.nmea_cb） {D（"report，timestamp=％llx，％llu"，r->fix.timestamp，r->fix.timestamp）;            r->callback.nmea_cb（ r->fix.timestamp，r->in，r->pos ）;                   }    ＃elser->callback=_gps_state.callbacks->location_cb;//r->callback.nmea_cb=_gps_state->callbacks.nmea_cb;        if （r->callback） {D（"if2 （r->callback.location_cb）"）;             r->callback（ &r->fix ）;             r->fix.flags = 0;         }        ＃endif        }    }    else if （ !memcmp（tok.p， "VTG"， 3） ） {     Token tok_fixStatus = nmea_tokenizer_get（tzer，9）;     if （tok_fixStatus.p[0] != """" && tok_fixStatus.p[0] != ""N""） {     Token tok_bearing = nmea_tokenizer_get（tzer，1）;     Token tok_speed = nmea_tokenizer_get（tzer，5）;     nmea_reader__bearing（ r， tok_bearing ）;     nmea_reader__speed （ r， tok_speed ）;     }    }    else if （ !memcmp（tok.p， "ZDA"， 3） ） {     Token tok_time;     Token tok_year = nmea_tokenizer_get（tzer，4）;     if （tok_year.p[0] != """"） {     Token tok_day = nmea_tokenizer_get（tzer，2）;     Token tok_mon = nmea_tokenizer_get（tzer，3）;     nmea_reader__cdate（ r， tok_day， tok_mon， tok_year ）;     }     tok_time = nmea_tokenizer_get（tzer，1）;     if （tok_time.p[0] != """"）     nmea_reader__time（r， tok_time）;    }    else {     tok.p -= 2;     D（"unknown sentence ""％.*s"， tok.end-tok.p， tok.p）;    }D（"％s，％d，"，__FILE__，__LINE__）;    if （r->fix.flags!=0） {＃if GPS_DEBUGD（"％d，flags=％d"，__LINE__，r->fix.flags）;        char temp[256];        char* p = temp;        char* end = p + sizeof（temp）;        struct tm utc;        p += snprintf（ p， end-p， "sending fix" ）;        if （r->fix.flags & GPS_LOCATION_HAS_LAT_LONG） {            p += snprintf（p， end-p， " lat=％g lon=％g"， r->fix.latitude， r->fix.longitude）;        }        if （r->fix.flags & GPS_LOCATION_HAS_ALTITUDE） {            p += snprintf（p， end-p， " altitude=％g"， r->fix.altitude）;        }        if （r->fix.flags & GPS_LOCATION_HAS_SPEED） {            p += snprintf（p， end-p， " speed=％g"， r->fix.speed）;        }        if （r->fix.flags & GPS_LOCATION_HAS_BEARING） {            p += snprintf（p， end-p， " bearing=％g"， r->fix.bearing）;        }        if （r->fix.flags & GPS_LOCATION_HAS_ACCURACY） {            p += snprintf（p，end-p， " accuracy=％g"， r->fix.accuracy）;        }        gmtime_r（ （time_t*） &r->fix.timestamp， &utc ）;        p += snprintf（p， end-p， " time=％s"， asctime（ &utc ） ）;        D（temp）;//added by mayzhang for debugD（"******************************1％s，％d:％s，may callback***************************"，__FILE__，__LINE__，__FUNCTION__）;＃endifD（"******************************2％s，％d:％s，may callback***************************"，__FILE__，__LINE__，__FUNCTION__）;   }                else {             /* D（"no callback， keeping data until needed !"）; */        }    }