/Eclair/hardware/libhardware_legacy/include/hardware_legacy/gps.h
typedef struct {
/** Contains GpsLocationFlags bits. */
uint16_t flags;
/** Represents latitude in degrees. */
double latitude;
/** Represents longitude in degrees. */
double longitude;
/** 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是標識
#define GPS_LOCATION_HAS_LAT_LONG 0x0001, flags 的bit0為1時,標識位置信息有經緯度的信息
/** GpsLocation has valid altitude. */
#define GPS_LOCATION_HAS_ALTITUDE 0x0002,flags 的bit1為1時,標識位置信息有高度的信息,以下標識位類似。
/** GpsLocation has valid speed. */
#define GPS_LOCATION_HAS_SPEED 0x0004
/** GpsLocation has valid bearing. */
#define GPS_LOCATION_HAS_BEARING 0x0008
/** GpsLocation has valid accuracy. */
#define GPS_LOCATION_HAS_ACCURACY 0x0010
typedef void (* gps_status_callback)(GpsStatus* status);
可以使用這個函數提交標識信息。
timestamp時間戳
是一個64位的無符號的整數。它原本的定義是,UTC時間從1970年01月01日00:00:00至現在的秒數。但是在android的Java語言中Date的構造函數必須輸入毫秒值,但得到的十進制是秒,所以要乘以1000。
bearing
對應著RMC的第8(從0起)個數據斷。對地航向(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
如果收到如下數據報$GPGSA,A,3,07,19,08,03,16,11,06,,,,,,2.8,1.5,2.3*38
07 , 19 , 08 ,03 , 16 , 11 , 06 是有用的衛星編號(prn)used_in_fix_mask的
bit 6 , 18 , 7 , 2 , 15 , 10 , 5 為1,其它位為0.(bit0也是0)
ephemeris_mask,almanac_mask
這兩個掩碼,與GSV信息密切相關。
比如收到如下的信息。(為瞭便於數據分析我多加瞭轉行)
$GPGSV,3,1,11,
19,79,359,30,
13,47,260,22,
03,46,029,31,
23,40,217,24*7B
衛星編號(prn)19,13,03,23
$GPGSV,3,2,11,
11,37,180,,
06,33,036,29,
16,30,050,35,
07,27,324,25*7A
衛星編號(prn)11,6,16,07
$GPGSV,3,3,11,
24,17,178,,
08,03,319,
28,31,02,133,*4C
衛星編號(prn)24,08,28
ephemeris_mask和almanac_mask的bit(18,12,02,22,10,5,15,06, 23,07,27)為1,其它位為0(bit從第0位開始),
掩碼的值與衛星編號是緊密相關的。
總之,要對NEMA數據格式有深刻的瞭解。
貼出主要代碼:Eclair/hardware/libhardware_legacy/gps/gps_qemu.c
歡迎交流。
Java代碼
<pre name="code" class="cpp">static void
nmea_reader_parse( NmeaReader* r )
{D("%s,%d,%s\n",__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\n",__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_update_time(r, tok_time);
nmea_reader_update_latlong(r, tok_latitude,
tok_latitudeHemi.p[0],
tok_longitude,
tok_longitudeHemi.p[0]);
nmea_reader_update_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_update_time(r, tok_time);
nmea_reader_update_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\n",__FILE__,__LINE__,__FUNCTION__);
Token tok_noSatellites = nmea_tokenizer_get(tzer, 3);
int noSatellites = str2int(tok_noSatellites.p, tok_noSatellites.end);
D("%d,inview=%d,\n",__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\n",__LINE__,sentence,totalSentences);
int curr;
int i;
if (sentence == 1) {
D("msg_index=%d\n",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\n",curr);
D("%d,prn=%d:snr=%f\n",__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_Version
r->callback.sv_status_cb=_gps_state->callbacks.sv_status_cb;
if (r->sv_status_changed !=0) {
if (r->callback.sv_status_cb) {
#if GPS_DEBUG
D("%d,SV_STATSU,change=%d\n",__LINE__,r->sv_status_changed);
int nums=r->sv_status.num_svs;
D("num_svs=%d,emask=%x,amask=%x,inusemask=%x\n",r->sv_status.num_svs,r->sv_status.ephemeris_mask,r->sv_status.almanac_mask,r->sv_status.used_in_fix_mask);
D("************88\n");
while(nums)
{
nums–;
D("prn=%d:snr=%f\n",r->sv_status.sv_list[nums].prn,r->sv_status.sv_list[nums].snr);
}D("************88\n");
#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\n",__FILE__,__LINE__,__FUNCTION__);
Token tok_fixStatus = nmea_tokenizer_get(tzer, 2);
int i;
if (tok_fixStatus.p[0] != '\0' && tok_fixStatus.p[0] != '1') {
Token tok_accuracy = nmea_tokenizer_get(tzer, 15);//position dilution of precision dop
nmea_reader_update_accuracy(r, tok_accuracy);
r->sv_status.used_in_fix_mask = 0ul;
D("\n");
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("\n");
D("%s: fix mask is %x", __FUNCTION__, r->sv_status.used_in_fix_mask);
// D(" [log hit][%s:%d] fix.flags=0x%x ", __FUNCTION__, __LINE__, r->fix.flags);
}
D(" [log hit][%s:%d] fix.flags=0x%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_update_date( r, tok_date, tok_time );
nmea_reader_update_latlong( r, tok_latitude,
tok_latitudeHemi.p[0],
tok_longitude,
tok_longitudeHemi.p[0] );
nmea_reader_update_bearing( r, tok_bearing );
nmea_reader_update_speed ( r, tok_speed );
#ifdef Svpnd_Version
r->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\n",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\n",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\n",r->fix.timestamp,r->fix.timestamp);
r->callback.nmea_cb( r->fix.timestamp,r->in,r->pos );
}
#else
r->callback=_gps_state.callbacks->location_cb;
//r->callback.nmea_cb=_gps_state->callbacks.nmea_cb;
if (r->callback) {D("if2 (r->callback.location_cb)\n");
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] != '\0' && tok_fixStatus.p[0] != 'N') {
Token tok_bearing = nmea_tokenizer_get(tzer,1);
Token tok_speed = nmea_tokenizer_get(tzer,5);
nmea_reader_update_bearing( r, tok_bearing );
nmea_reader_update_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] != '\0') {
Token tok_day = nmea_tokenizer_get(tzer,2);
Token tok_mon = nmea_tokenizer_get(tzer,3);
nmea_reader_update_cdate( r, tok_day, tok_mon, tok_year );
}
tok_time = nmea_tokenizer_get(tzer,1);
if (tok_time.p[0] != '\0')
nmea_reader_update_time(r, tok_time);
}
else {
tok.p -= 2;
D("unknown sentence '%.*s", tok.end-tok.p, tok.p);
}D("%s,%d,\n",__FILE__,__LINE__);
if (r->fix.flags!=0) {
#if GPS_DEBUG
D("%d,flags=%d\n",__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 debug
D("******************************1\n%s,%d:%s,may callback\n***************************\n",__FILE__,__LINE__,__FUNCTION__);
#endif
D("******************************2\n%s,%d:%s,may callback\n***************************\n",__FILE__,__LINE__,__FUNCTION__);
}
else {
/* D("no callback, keeping data until needed !"); */
}
}
作者“極客網絡”