nmea_8c-source.html

ATMEL的AVR单片机库文件

00108 
00109     <span class="keywordflow">if</span>(foundpacket)
00110     {
00111         <span class="comment">// check message type and process appropriately</span>
00112         <span class="keywordflow">if</span>(!strncmp(NmeaPacket, <span class="stringliteral">"GPGGA"</span>, 5))
00113             nmeaProcessGPGGA(NmeaPacket);
00114         <span class="keywordflow">else</span> <span class="keywordflow">if</span>(!strncmp(NmeaPacket, <span class="stringliteral">"GPVTG"</span>, 5))
00115             nmeaProcessGPVTG(NmeaPacket);
00116     }
00117     <span class="keywordflow">return</span> foundpacket;
00118 }
00119 
00120 <span class="keywordtype">void</span> nmeaProcessGPGGA(u08* packet)
00121 {
00122     u08 i;
00123     <span class="keywordtype">char</span>* endptr;
00124 
00125     <span class="keywordflow">if</span>(debug)
00126     {
00127         rprintf(<span class="stringliteral">"NMEA: "</span>);
00128         <a class="code" href="rprintf_8h.html#a8">rprintfStr</a>(packet);
00129         <a class="code" href="rprintf_8c.html#a9">rprintfCRLF</a>();
00130     }
00131 
00132     <span class="comment">// start parsing just after "GPGGA,"</span>
00133     i = 6;
00134 
00135     <span class="comment">// get UTC time [hhmmss.sss]</span>
00136     GpsInfo.PosLLA.TimeOfFix.f = strtod(&amp;packet[i], &amp;endptr);
00137     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: latitude</span>
00138     
00139     <span class="comment">// get latitude [ddmm.mmmmm]</span>
00140     GpsInfo.PosLLA.lat.f = strtod(&amp;packet[i], &amp;endptr);
00141     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: N/S indicator</span>
00142     
00143     <span class="comment">// correct latitute for N/S</span>
00144     <span class="keywordflow">if</span>(packet[i] == <span class="charliteral">'S'</span>) GpsInfo.PosLLA.lat.f = -GpsInfo.PosLLA.lat.f;
00145     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: longitude</span>
00146     
00147     <span class="comment">// get longitude [ddmm.mmmmm]</span>
00148     GpsInfo.PosLLA.lon.f = strtod(&amp;packet[i], &amp;endptr);
00149     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: E/W indicator</span>
00150 
00151     <span class="comment">// correct latitute for E/W</span>
00152     <span class="keywordflow">if</span>(packet[i] == <span class="charliteral">'W'</span>) GpsInfo.PosLLA.lon.f = -GpsInfo.PosLLA.lon.f;
00153     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: position fix status</span>
00154 
00155     <span class="comment">// position fix status</span>
00156     <span class="comment">// 0 = Invalid, 1 = Valid SPS, 2 = Valid DGPS, 3 = Valid PPS</span>
00157     <span class="comment">// check for good position fix</span>
00158     <span class="keywordflow">if</span>( (packet[i] != <span class="charliteral">'0'</span>) &amp;&amp; (packet[i] != <span class="charliteral">','</span>) )
00159         GpsInfo.PosLLA.updates++;
00160     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: satellites used</span>
00161     
00162     <span class="comment">// get number of satellites used in GPS solution</span>
00163     GpsInfo.numSVs = atoi(&amp;packet[i]);
00164     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: HDOP (horizontal dilution of precision)</span>
00165     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: altitude</span>
00166     
00167     <span class="comment">// get altitude (in meters)</span>
00168     GpsInfo.PosLLA.alt.f = strtod(&amp;packet[i], &amp;endptr);
00169 
00170     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: altitude units, always 'M'</span>
00171     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: geoid seperation</span>
00172     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: seperation units</span>
00173     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: DGPS age</span>
00174     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: DGPS station ID</span>
00175     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">'*'</span>);              <span class="comment">// next field: checksum</span>
00176 }
00177 
00178 <span class="keywordtype">void</span> nmeaProcessGPVTG(u08* packet)
00179 {
00180     u08 i;
00181     <span class="keywordtype">char</span>* endptr;
00182 
00183     <span class="keywordflow">if</span>(debug)
00184     {
00185         rprintf(<span class="stringliteral">"NMEA: "</span>);
00186         <a class="code" href="rprintf_8h.html#a8">rprintfStr</a>(packet);
00187         <a class="code" href="rprintf_8c.html#a9">rprintfCRLF</a>();
00188     }
00189 
00190     <span class="comment">// start parsing just after "GPVTG,"</span>
00191     i = 6;
00192     <span class="comment">// get course (true north ref) in degrees [ddd.dd]</span>
00193     GpsInfo.VelHS.heading.f = strtod(&amp;packet[i], &amp;endptr);
00194     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: 'T'</span>
00195     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: course (magnetic north)</span>
00196 
00197     <span class="comment">// get course (magnetic north ref) in degrees [ddd.dd]</span>
00198     <span class="comment">//GpsInfo.VelHS.heading.f = strtod(&amp;packet[i], &amp;endptr);</span>
00199     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: 'M'</span>
00200     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: speed (knots)</span>
00201 
00202     <span class="comment">// get speed in knots</span>
00203     <span class="comment">//GpsInfo.VelHS.speed.f = strtod(&amp;packet[i], &amp;endptr);</span>
00204     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: 'N'</span>
00205     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: speed (km/h)</span>
00206 
00207     <span class="comment">// get speed in km/h</span>
00208     GpsInfo.VelHS.speed.f = strtod(&amp;packet[i], &amp;endptr);
00209     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">','</span>);              <span class="comment">// next field: 'K'</span>
00210     <span class="keywordflow">while</span>(packet[i++] != <span class="charliteral">'*'</span>);              <span class="comment">// next field: checksum</span>
00211 
00212     GpsInfo.VelHS.updates++;
00213 }
00214 
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