Thom Bronez
Revised Embedded Artists' MTK3339 library to save all raw GPS messages and enable optional decoding of RMC message.
Fork of
MTK3339
by 
EmbeddedArtists AB
Diff: MTK3339.cpp
- Revision:
- 1:3057ad6a5d4b
- Parent:
- 0:bd0fe2412980
- Child:
- 2:2391d165df47
--- a/MTK3339.cpp Thu Nov 07 11:46:53 2013 +0000
+++ b/MTK3339.cpp Fri Jul 31 21:20:55 2015 +0000
@@ -1,16 +1,33 @@
+// Class to represent serial interface to MTK3339 GPS chip
+// Original author: Embedded Artists
+// Revised by T. Bronez, 2015-05-28
#include "mbed.h"
#include "MTK3339.h"
+#define min(a,b) a>b?a:b
+DigitalOut led2(LED2);
+Timeout timeout2;
+void led2Off() {
+ led2 = 1;
+}
+void flashLED2() {
+ led2 = 0;
+ timeout2.attach(&led2Off, 0.1);
+}
MTK3339::MTK3339(PinName tx, PinName rx) : _serial(tx, rx) {
_serial.baud(9600);
-
_state = StateStart;
_sentenceMask = 0;
- _availDataType = NmeaInvalid;
- memset(&gga, 0, sizeof(GgaType));
- memset(&vtg, 0, sizeof(VtgType));
+ _availDataType = NMEA_NONE;
+ memset(&rmc, 0, sizeof(RmcType));
+
+ memset(&ggaMsg, 0, MSG_BUF_SZ);
+ memset(&gsaMsg, 0, MSG_BUF_SZ);
+ memset(&gsvMsg, 0, MSG_BUF_SZ);
+ memset(&rmcMsg, 0, MSG_BUF_SZ);
+ memset(&vtgMsg, 0, MSG_BUF_SZ);
}
void MTK3339::start(void (*fptr)(void), int mask) {
@@ -18,7 +35,7 @@
_dataCallback.attach(fptr);
_sentenceMask = mask;
_serial.attach(this, &MTK3339::uartIrq, Serial::RxIrq);
- }
+ }
}
void MTK3339::stop() {
@@ -31,156 +48,206 @@
return _availDataType;
}
-double MTK3339::getLatitudeAsDegrees() {
- if(gga.fix == 0 || gga.nsIndicator == 0) return 0;
-
- double l = gga.latitude;
- char ns = gga.nsIndicator;
-
- // convert from ddmm.mmmm to degrees only
- // 60 minutes is 1 degree
-
- int deg = (int)(l / 100);
- l = (l - deg*100.0) / 60.0;
- l = deg + l;
- if (ns == 'S') l = -l;
+void MTK3339::decodeRMC() {
+ // See http://aprs.gids.nl/nmea/#rmc for RMC sentence definition
+ const double sixtieth = 1.0/60.0;
+ int n = 0; // scratch int for conversions
+ double d = 0; // scratch double for conversions
+ char* q = NULL; // scratch pointer for conversions
+
+ memset(&rmc, 0, sizeof(RmcType));
+ char* p = rmcMsg;
+
+ /**
+ * Find and decode field 0, UTC time, as hhmmss.sss
+ */
+ p = strchr(p, ','); // First comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ q = p;
+ // Decode time hours
+ n = ((*q++) - 48)*10; // tens
+ n += ((*q++) - 48); // ones
+ rmc.gps_tm.tm_hour = n;
+ // Decode time minutes
+ n = ((*q++) - 48)*10; // tens
+ n += ((*q++) - 48); // ones
+ rmc.gps_tm.tm_min = n;
+ // Decode time seconds
+ n = ((*q++) - 48)*10; // tens
+ n += ((*q++) - 48); // ones
+ rmc.gps_tm.tm_sec = n;
+ // Decode time milliseconds
+ q++; // decimal point
+ n = ((*q++) - 48)*100; // hundreds of msec = tenths of second
+ n += ((*q++) - 48)*10; // tens of msec = hundredths of second
+ n += ((*q++) - 48); // ones of msec = thousandths of second
+ rmc.msec = n;
+
+ /**
+ * Find and decode field 1, GPS status, as single
+ * character 'A' for valid or 'V' for invalid
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ if (*p == 'A' || *p == 'V')
+ rmc.status = *p;
+ else
+ rmc.status = ' ';
+
+ /**
+ * Find and decode field 2, latitude, formatted as ddmm.mmmm
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ q = p;
+ d = ((*q++) - 48)*10; // tens
+ d += ((*q++) - 48); // ones
+ rmc.lat_dd = d; // whole degrees
- return l;
-}
+ d = ((*q++) - 48)*10; // tens
+ d += ((*q++) - 48); // ones
+ q++; // decimal point
+ d += ((*q++) - 48)*0.1000; // tenths
+ d += ((*q++) - 48)*0.0100; // hundredths
+ d += ((*q++) - 48)*0.0010; // thousandths
+ d += ((*q++) - 48)*0.0001; // ten-thousandths
+ if (*q == ',')
+ rmc.lat_dd += sixtieth*d; // decimal degrees
+ else
+ rmc.lat_dd = NAN; // Unexpected
+
+ /**
+ * Find and decode field 3, latitude sense, as single
+ * character 'N' for north or 'S' for south
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
-double MTK3339::getLongitudeAsDegrees() {
- if(gga.fix == 0 || gga.ewIndicator == 0) return 0;
-
- double l = gga.longitude;
- char ew = gga.ewIndicator;
+ if (*p == 'S') rmc.lat_dd = -rmc.lat_dd;
+
+ /**
+ * Find and decode field 4, longitude, formatted as dddmm.mmmm
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ q = p;
+ d = ((*q++) - 48)*100; // hundreds
+ d += ((*q++) - 48)*10; // tens
+ d += ((*q++) - 48); // ones
+ rmc.lon_dd = d; // whole degrees
- // convert from ddmm.mmmm to degrees only
- // 60 minutes is 1 degree
+ d = ((*q++) - 48)*10; // tens
+ d += ((*q++) - 48); // ones
+ q++; // decimal point
+ d += ((*q++) - 48)*0.1000; // tenths
+ d += ((*q++) - 48)*0.0100; // hundredths
+ d += ((*q++) - 48)*0.0010; // thousandths
+ d += ((*q++) - 48)*0.0001; // ten-thousandths
+ if (*q == ',')
+ rmc.lon_dd += sixtieth*d; // decimal degrees
+ else
+ rmc.lon_dd = NAN; // Unexpected
+
+ /**
+ * Find and decode field 5, longitude sense, as single
+ * character 'E' for east or 'W' for west
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ if (*p == 'W') rmc.lon_dd = -rmc.lon_dd;
- int deg = (int)(l / 100);
- l = (l - deg*100) / 60;
- l = deg + l;
- if (ew == 'W') l = -l;
-
- return l;
+ /**
+ * Find and skip field 6, speed in knots
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ /**
+ * Find and skip field 7, course in degrees
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ /**
+ * Find and decode field 8, UTC date, formatted as ddmmyy
+ * where 1<=dd<=31, 1<=mm<=12, and yy is offset from 2000
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ q = p;
+ // Decode date day
+ n = ((*q++) - 48)*10; // tens
+ n += ((*q++) - 48); // ones
+ rmc.gps_tm.tm_mday = n;
+ // Decode date month
+ n = ((*q++) - 48)*10; // tens
+ n += ((*q++) - 48); // ones
+ rmc.gps_tm.tm_mon = n-1; // tm_mon runs 0-11, not 1-12
+ // Decode date year
+ n = ((*q++) - 48)*10; // tens
+ n += ((*q++) - 48); // ones
+ rmc.gps_tm.tm_year = n+100; // tm_year is offset from year 1900, not 2000
+
+ /**
+ * Find and skip field 9, magnetic variation
+ * (not implemented in GPS firmware)
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
+
+ /**
+ * Find and skip field 10, magnetic variation direction
+ * (not implemented in GPS firmware)
+ */
+ p = strchr(p, ','); // Next comma
+ if (p == NULL || *p == 0) return; // Unexpected
+ p++; // Start of field
}
-void MTK3339::parseGGA(char* data, int dataLen) {
- //http://aprs.gids.nl/nmea/#gga
-
- double tm = 0;
-
- memset(&gga, 0, sizeof(GgaType));
-
- char* p = data;
- int pos = 0;
-
- p = strchr(p, ',');
- while (p != NULL && *p != 0) {
- p++;
-
- switch(pos) {
- case 0: // time: hhmmss.sss
- tm = strtod(p, NULL);
- gga.hours = (int)(tm / 10000);
- gga.minutes = ((int)tm % 10000) / 100;
- gga.seconds = ((int)tm % 100);
- gga.milliseconds = (int)(tm * 1000) % 1000;
- break;
- case 1: // latitude: ddmm.mmmm
- gga.latitude = strtod(p, NULL);
- break;
- case 2: // N/S indicator (north or south)
- if (*p == 'N' || *p == 'S') {
- gga.nsIndicator = *p;
- }
- break;
- case 3: // longitude: dddmm.mmmm
- gga.longitude = strtod(p, NULL);
- break;
- case 4: // E/W indicator (east or west)
- if (*p == 'E' || *p == 'W') {
- gga.ewIndicator = *p;
- }
- break;
- case 5: // position indicator (1=no fix, 2=GPS fix, 3=Differential)
- gga.fix = strtol(p, NULL, 10);
- break;
- case 6: // num satellites
- gga.satellites = strtol(p, NULL, 10);
- break;
- case 7: // hdop
- gga.hdop = strtod(p, NULL);
- break;
- case 8: // altitude
- gga.altitude = strtod(p, NULL);
- break;
- case 9: // units
- // ignore units
- break;
- case 10: // geoidal separation
- gga.geoidal = strtod(p, NULL);
- break;
- }
- pos++;
-
- p = strchr(p, ',');
- }
-
+void MTK3339::saveGGA(char* data, int dataLen) {
+ // See http://aprs.gids.nl/nmea/#gga for GGA sentence definition
+ memcpy (ggaMsg, data, min(dataLen, MSG_BUF_SZ));
+}
+
+void MTK3339::saveGSA(char* data, int dataLen) {
+ // See http://aprs.gids.nl/nmea/#gsa for GSA sentence definition
+ memcpy (gsaMsg, data, min(dataLen, MSG_BUF_SZ));
}
-void MTK3339::parseVTG(char* data, int dataLen) {
-
-
- char* p = data;
- int pos = 0;
-
- memset(&vtg, 0, sizeof(VtgType));
-
- p = strchr(p, ',');
- while (p != NULL && *p != 0) {
- p++;
-
- switch(pos) {
- case 0: // course in degrees
- vtg.course = strtod(p, NULL);
- break;
- case 1: // Reference (T)
- break;
- case 2: // course magnetic (need customization)
- break;
- case 3: // reference (M)
- break;
- case 4: // speed in knots
- vtg.speedKnots = strtod(p, NULL);
- break;
- case 5: // units (N)
- break;
- case 6: // speed in Km/h
- vtg.speedKmHour = strtod(p, NULL);
- break;
- case 7: // units (K)
- break;
- case 8: // mode
- if (*p == 'A' || *p == 'D' || *p == 'E') {
- vtg.mode = *p;
- }
-
- break;
-
- }
-
- pos++;
-
- p = strchr(p, ',');
- }
+void MTK3339::saveGSV(char* data, int dataLen) {
+ // See http://aprs.gids.nl/nmea/#gsv for GSV sentence definition
+ memcpy (gsvMsg, data, min(dataLen, MSG_BUF_SZ));
}
+void MTK3339::saveRMC(char* data, int dataLen) {
+ // See http://aprs.gids.nl/nmea/#rmc for RMC sentence definition
+ memcpy (rmcMsg, data, min(dataLen, MSG_BUF_SZ));
+}
-void MTK3339::parseData(char* data, int len) {
+void MTK3339::saveVTG(char* data, int dataLen) {
+ // See http://aprs.gids.nl/nmea/#vtg for VTG sentence definition
+ memcpy (vtgMsg, data, min(dataLen, MSG_BUF_SZ));
+}
+
+void MTK3339::saveData(char* data, int len) {
do {
-
- // verify checksum
+ // Verify checksum
if (len < 3 || (len > 3 && data[len-3] != '*')) {
// invalid data
break;
@@ -192,32 +259,47 @@
if (sum != 0) {
// invalid checksum
break;
- }
-
-
- if (strncmp("$GPGGA", data, 6) == 0 && (_sentenceMask & NmeaGga) != 0) {
- parseGGA(data, len);
- _availDataType = NmeaGga;
+ }
+
+ // Save appropriate sentence for later decoding
+ if (strncmp("$GPRMC", data, 6) == 0 && (_sentenceMask & NMEA_RMC) != 0) {
+ flashLED2();
+ saveRMC(data, len);
+ _availDataType = NMEA_RMC;
_dataCallback.call();
- _availDataType = NmeaInvalid;
+ _availDataType = NMEA_NONE;
+ }
+ else if (strncmp("$GPGGA", data, 6) == 0 && (_sentenceMask & NMEA_GGA) != 0) {
+ saveGGA(data, len);
+ _availDataType = NMEA_GGA;
+ _dataCallback.call();
+ _availDataType = NMEA_NONE;
}
- else if (strncmp("$GPVTG", data, 6) == 0 && (_sentenceMask & NmeaVtg) != 0) {
- parseVTG(data, len);
- _availDataType = NmeaVtg;
+ else if (strncmp("$GPGSA", data, 6) == 0 && (_sentenceMask & NMEA_GSA) != 0) {
+ saveGSA(data, len);
+ _availDataType = NMEA_GSA;
_dataCallback.call();
- _availDataType = NmeaInvalid;
- }
-
-
+ _availDataType = NMEA_NONE;
+ }
+ else if (strncmp("$GPGSV", data, 6) == 0 && (_sentenceMask & NMEA_GSV) != 0) {
+ saveGSV(data, len);
+ _availDataType = NMEA_GSV;
+ _dataCallback.call();
+ _availDataType = NMEA_NONE;
+ }
+ else if (strncmp("$GPVTG", data, 6) == 0 && (_sentenceMask & NMEA_VTG) != 0) {
+ saveVTG(data, len);
+ _availDataType = NMEA_VTG;
+ _dataCallback.call();
+ _availDataType = NMEA_NONE;
+ }
} while(0);
}
void MTK3339::uartIrq() {
char d = 0;
-
while(_serial.readable()) {
d = _serial.getc();
-
switch(_state) {
case StateStart:
if (d == '$') {
@@ -232,18 +314,15 @@
_state = StateStart;
}
else if (d == '\r') {
-
_buf[_bufPos] = 0;
-
- parseData(_buf, _bufPos);
-
+ saveData(_buf, _bufPos);
_state = StateStart;
}
else {
_buf[_bufPos++] = d;
}
-
break;
}
}
}
+