Nile Mittow
Example code for reading from a serial GPS unit & parsing an RMC GPS string to a struct.
Fork of
mbed_blinky
by 
Mbed
Revision 16:1bf12f0bb4b9, committed 2017-03-09
- Comitter:
- HackerLabATTKit01
- Date:
- Thu Mar 09 21:21:17 2017 +0000
- Parent:
- 15:165ecc5f4280
- Child:
- 17:15322357429b
- Commit message:
- Example code for reading from a serial GPS unit & parsing an RMC GPS string into a struct.
Changed in this revision
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/GPRMCSentence.h Thu Mar 09 21:21:17 2017 +0000
@@ -0,0 +1,161 @@
+#define TIMEMAX 6
+#define LATMAX 20
+#define LONGMAX 20
+#define SPEEDMAX 6
+#define TRACKMAX 6
+#define DATEMAX 6
+#define MAGVARMAX 6
+#define CHECKSUMMAX 10
+#define DEVNULMAX 20
+
+#define CRLF2 "\n\r"
+
+/** Tfile provides a means for parsing serially received GPRMC sentences into a location struct **/
+
+typedef struct {
+ char time[TIMEMAX+1];
+ char status;
+ char latitude[LATMAX+1];
+ double dlatitude;
+ char latdir;
+ char longitude[LONGMAX+1];
+ double dlongitude;
+ char longdir;
+ char speed[SPEEDMAX+1];
+ char trackangle[TRACKMAX+1];
+ char date[DATEMAX+1];
+ char magvar[MAGVARMAX+1];
+ char magvardir;
+ //char checksum[CHECKSUMMAX+1];
+} GPRMCSentence;
+
+double charStrToDouble(char* str) {
+ uint16_t decpos = 0;
+ double num = 0.0;
+ while((str[decpos]!='.')&&(str[decpos]!='\0')) decpos++;
+ double multiplier = 1.0;
+ for(uint16_t i = 1;(decpos-i)>=0;i++) {
+ num += (multiplier*(str[decpos-i]-48));
+ multiplier *= 10.0;
+ }
+ multiplier = (1.0/10.0);
+ for(uint16_t i = 1;str[decpos+i]!='\0';i++) {
+ num += (multiplier*(str[decpos+i]-48));
+ multiplier /= 10.0;
+ }
+ return num;
+}
+
+uint16_t parseStringToGPRMCStructEntry(char* gprmcstr, char* gprmcentry, uint16_t start, uint16_t length) {
+ int16_t i=0;
+ while((gprmcstr[start] != ',') &&
+ (gprmcstr[start] != '\0') &&
+ (gprmcstr[start] != '\n') &&
+ (i < length)) {
+ gprmcentry[i] = gprmcstr[start];
+ start++;i++;
+ }
+ while(i<=length) {
+ gprmcentry[i] = '\0';
+ i++;
+ }
+ return start + 1;
+}
+
+void moveDecimalLeft(char* num, uint16_t places) {
+ if (places == 0) return;
+ else places--;
+ uint16_t i = 0;
+ while(num[i] != '\0') {
+ if ((i >= places) && (num[i] == '.')) {
+ uint16_t j;
+ for(j=i;j>(i-places);j--) num[j] = num[j-1];
+ num[j] = num[j-1];
+ num[j-1] = '.';
+ break;
+ }
+ else i++;
+ }
+}
+
+void negateCharStrNumber(char* num, uint16_t len) {
+ for(uint16_t i=(len-1); i>0;i--) num[i] = num[i-1];
+ num[0] = '-';
+}
+
+/************************
+parseGPRMCStrToStruct:
+
+In: gprmcstr: raw char array string of gprmc sentence
+In: GPRMCSentece: struct object representing gprmc sentence to parse to
+
+Out: integer: < 0 : not a gprmc sentence
+ = 0 : not valid
+ > 0 : valid
+
+*/
+int8_t parseGPRMCStrToStruct(char* gprmcstr, GPRMCSentence* gprmstruct) {
+ uint16_t pos = 7;
+ char devnull[DEVNULMAX+1];
+ if ((gprmcstr[0] == '$') &&
+ (gprmcstr[1] == 'G') &&
+ (gprmcstr[2] == 'P') &&
+ (gprmcstr[3] == 'R') &&
+ (gprmcstr[4] == 'M') &&
+ (gprmcstr[5] == 'C') &&
+ (gprmcstr[6] == ',')) {
+ pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->time,pos,TIMEMAX);
+ //pos = parseStringToGPRMCStructEntry(gprmcstr,devnull,pos,DEVNULMAX); // to get rid of time decimal, needed for some gps modules
+ if (gprmcstr[pos] != ',') {gprmstruct->status = gprmcstr[pos];pos++;}
+ else gprmstruct->status = '\0';
+ pos++;
+
+ pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->latitude,pos,LATMAX);
+ moveDecimalLeft(gprmstruct->latitude,2);
+ gprmstruct->dlatitude = charStrToDouble(gprmstruct->latitude);
+ if (gprmcstr[pos] != ',') {gprmstruct->latdir = gprmcstr[pos];pos++;}
+ else gprmstruct->latdir = '\0';
+ if(gprmstruct->latdir == 'S') {
+ negateCharStrNumber(gprmstruct->latitude, LATMAX);
+ gprmstruct->dlatitude *= -1;
+ }
+ pos++;
+
+ pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->longitude,pos,LONGMAX);
+ moveDecimalLeft(gprmstruct->longitude,2);
+ gprmstruct->dlongitude = charStrToDouble(gprmstruct->longitude);
+ if (gprmcstr[pos] != ',') {gprmstruct->longdir = gprmcstr[pos];pos++;}
+ else gprmstruct->longdir = '\0';
+ if(gprmstruct->longdir == 'W') {
+ negateCharStrNumber(gprmstruct->longitude, LONGMAX);
+ gprmstruct->dlongitude *= -1;
+ }
+ pos++;
+
+ pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->speed,pos,SPEEDMAX);
+ pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->trackangle,pos,TRACKMAX);
+ pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->date,pos,DATEMAX);
+ pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->magvar,pos,MAGVARMAX);
+ if (gprmcstr[pos] != ',') {gprmstruct->magvardir = gprmcstr[pos];pos++;}
+ else gprmstruct->magvardir = '\0';
+ pos++;
+ //pos = parseStringToGPRMCStructEntry(gprmcstr,gprmstruct->checksum,pos,CHECKSUMMAX);
+ if (gprmstruct->status == 'A') return 1;
+ else return 0;
+ }
+ else return -1;
+}
+
+void printGPRMCSentence(GPRMCSentence* gprmcstruct, Serial *serial) {
+ serial->printf("Time: %s" CRLF2,gprmcstruct->time);
+ serial->printf("Status: %c" CRLF2,gprmcstruct->status);
+ serial->printf("Lat: %s" CRLF2,gprmcstruct->latitude);
+ serial->printf("LatDir: %c" CRLF2,gprmcstruct->latdir);
+ serial->printf("Long: %s" CRLF2,gprmcstruct->longitude);
+ serial->printf("LongDir: %c" CRLF2,gprmcstruct->longdir);
+ serial->printf("Speed: %s" CRLF2,gprmcstruct->speed);
+ serial->printf("Angle: %s" CRLF2,gprmcstruct->trackangle);
+ serial->printf("Date: %s" CRLF2,gprmcstruct->date);
+ serial->printf("MagVar: %s" CRLF2,gprmcstruct->magvar);
+ serial->printf("MagDir: %c" CRLF2,gprmcstruct->magvardir);
+}
--- a/main.cpp Wed Jan 18 13:46:04 2017 +0000
+++ b/main.cpp Thu Mar 09 21:21:17 2017 +0000
@@ -1,12 +1,80 @@
#include "mbed.h"
+#include "GPRMCSentence.h"
+
+#define GPSBUFFSIZE 256
+
+Serial pc(USBTX, USBRX); // tx, rx
+Serial xgps(PTC15, PTC14);
+
+unsigned gpsSentenceIndex = 0;
+char gpsSentence[GPSBUFFSIZE];
+volatile bool newline_detected = false;
+GPRMCSentence lastPosition;
-DigitalOut myled(LED1);
+void clearGpsSentence() {
+ for(int i=0;i<GPSBUFFSIZE;i++) gpsSentence[i] = '\0';
+ gpsSentenceIndex = 0;
+}
+
+int main() {
+ pc.printf("Where am I? ----------- \n");
+ clearGpsSentence();
+ while(1) {
+ gpsSentence[gpsSentenceIndex] = xgps.getc();
+ pc.putc(gpsSentence[gpsSentenceIndex]);
+ gpsSentenceIndex++;
+ if(gpsSentence[gpsSentenceIndex - 1] == '\n') {
+ gpsSentence[gpsSentenceIndex] = '\0';
+ if (parseGPRMCStrToStruct(gpsSentence, &lastPosition) >= 0) {
+ pc.printf("time: %s Status: %c \n\r" , lastPosition.time, lastPosition.status);
+ pc.printf("Lat : %s %c \n\r" , lastPosition.latitude, lastPosition.latdir);
+ pc.printf("Long: %s %c \n\r" , lastPosition.longitude, lastPosition.longdir);
+ }
+ clearGpsSentence();
+ }
+ }
+}
+
+
+/*include "mbed.h"
+
+DigitalOut rled(LED_RED);
+DigitalOut gled(LED_GREEN);
+DigitalOut bled(LED_BLUE);
int main() {
while(1) {
- myled = 1;
+ rled = 0;
+ gled = 0;
+ bled = 0;
+ wait(0.2);
+ rled = 0;
+ gled = 0;
+ bled = 1;
+ wait(0.2);
+ rled = 0;
+ gled = 1;
+ bled = 0;
+ wait(0.2);
+ rled = 0;
+ gled = 1;
+ bled = 1;
wait(0.2);
- myled = 0;
+ rled = 1;
+ gled = 0;
+ bled = 0;
+ wait(0.2);
+ rled = 1;
+ gled = 0;
+ bled = 1;
+ wait(0.2);
+ rled = 1;
+ gled = 1;
+ bled = 0;
+ wait(0.2);
+ rled = 1;
+ gled = 1;
+ bled = 1;
wait(0.2);
}
-}
+}*/
--- a/mbed.bld Wed Jan 18 13:46:04 2017 +0000 +++ b/mbed.bld Thu Mar 09 21:21:17 2017 +0000 @@ -1,1 +1,1 @@ -http://mbed.org/users/mbed_official/code/mbed/builds/ad3be0349dc5 \ No newline at end of file +http://mbed.org/users/mbed_official/code/mbed/builds/e1686b8d5b90 \ No newline at end of file