bool GPS_parseGPRMCSentence(const char * pSentence, GPS_DATA * pData)
{
/* Refer to http://www.gpsinformation.org/dale/nmea.htm#RMS
* Sample Data: $GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A
* Where:
* RMC Recommended Minimum sentence C
* 123519 Fix taken at 12:35:19 UTC
* A Status A=active or V=Void.
* 4807.038,N Latitude 48 deg 07.038' N
* 01131.000,E Longitude 11 deg 31.000' E
* 022.4 Speed over the ground in knots
* 084.4 Track angle in degrees True
* 230394 Date - 23rd of March 1994
* 003.1,W Magnetic Variation
* 6A The checksum data, always begins with *
*/
if (!pSentence || !pData) { return false; } // NULL pointer check on arguments
bool success = true;
success &= strncmp(pSentence, "$GPRMC,", 7) == 0;
success &= rmcSentenceIsValid(pSentence);
if (success)
{
pSentence += 7; // Now pointing at first data, which is time
pSentence += parseHHMMSSTime(pSentence, &pData->hour, &pData->min, &pData->sec);
pSentence += skipToNextComma(pSentence); // Skip over any decimals in the time
pSentence += skipToNextComma(pSentence); // Skip over valid char and comma
pSentence += parseLatitude(pSentence, &pData->latitude) + 1; // +1 skips over comma
pSentence += parseLongitude(pSentence, &pData->longitude) + 1; // +1 skips over comma
pSentence += skipToNextComma(pSentence); // Skip over speed
pSentence += skipToNextComma(pSentence); // Skip over trackAngle
pSentence += parseHHMMSSTime(pSentence, &pData->dd, &pData->mm, &pData->yy);
}
return success;
}
/*****************************************************************************
** Function name: GPSRetreiveData
**
** Descriptions: Reads and parses the next set of GPS data.
**
** parameters: None
** Returned value: The parsed information
**
*****************************************************************************/
const gpsData* GPSRetreiveData(void)
{
uint8_t * pattern = (uint8_t*)"GPGGA";
while (1) {
uint8_t buf[100];
uint8_t ch = 0;
uint8_t *ptr = 0;
int index = 0;
// Retrieve the first byte
if (!UARTGetChar(&ch))
continue;
// look for "$GPGGA," header
if (ch != '$') {
continue;
}
// Retrieve the next six bytes
for (index=0; index<6; index++) {
buf[index] = UARTGetCharBlock();
}
//Check if its Global Positioning System fixed Data
if(hasPattern((uint8_t*)&buf, pattern) == 0) {
continue;
}
//Retrieve the data from the GPS module
for (index=0; index<100; index++) {
buf[index] = UARTGetCharBlock();
if (buf[index] == '\r') {
buf[index] = END_OF_MESSAGE;
break;
}
}
ptr = &buf[0];
//parse UTC time
parseUTC(&ptr);
//parse Latitude
parseLatitude(&ptr);
// parse N/S field
parseNSIndicator(&ptr);
// parse Longitude
parseLongitude(&ptr);
// parse E/W field
parseEWIndicator(&ptr);
// parse fix position
parseFixIndicator(&ptr);
// parse satellites
parseSatellites(&ptr);
// parse horizontal-dilution-of-precision field
parseHDOP(&ptr);
// parse altitude
parseAltitudes(&ptr);
break;
}
return &data;
}
