Emery Premeaux
GPS NMEA sentence reader for Nucleo boards.
I had a lot of trouble getting other GPS examples to work. So I took Edoardo De Marchi's code from 2014 and hacked it until it was working on newer hardware.
Advice:
- Start with confirming the module works in U-Center, and know the baud rate. Many older libraries assume 9600. Newer modules run at higher baud rates
- Use a good terminal program and confirm you have human readable messages starting with "$GNGGA" or "$GPGSV" or similar.
Comments in code include links to NMEA sentence guides:
- http://navspark.mybigcommerce.com/content/NMEA_Format_v0.1.pdf
- https://www.gpsinformation.org/dale/nmea.htm#nmea
Most libraries do not include sentence filters for the types of sentences output by my M8N (and perhaps other modules as well)
Most older versions of the MODSERIAL library do not update properly to support STM32. I have found and included a version of the lib which will compile without errors. However, when using it in my code, the NMEA sentence gets corrupted somehow (for example showing some HUGE [6 digit] Satellite count, etc.
Revision 2:c16325a7d225, committed 2019-07-04
- Comitter:
- epremeaux
- Date:
- Thu Jul 04 04:12:41 2019 +0000
- Parent:
- 1:acd907fbcbae
- Commit message:
- U-Blox-M8N GPS example for Nucleo-F401RE. Decodes additional NMEA sentences
Changed in this revision
--- a/MODSERIAL.lib Fri Aug 22 12:43:55 2014 +0000 +++ b/MODSERIAL.lib Thu Jul 04 04:12:41 2019 +0000 @@ -1,1 +1,1 @@ -http://mbed.org/users/edodm85/code/MODSERIAL/#4213f9a7c3ad +https://os.mbed.com/users/Sissors/code/MODSERIAL/#d2a5e26fd658
--- a/main.cpp Fri Aug 22 12:43:55 2014 +0000
+++ b/main.cpp Thu Jul 04 04:12:41 2019 +0000
@@ -2,16 +2,39 @@
* Author: Edoardo De Marchi
* Date: 22-08-14
* Notes: Firmware for GPS U-Blox NEO-6M
+ *
+ * Modified: Emery Premeaux
+ * Date: July 2019
+ * Written for: Nucleo F401RE & NEO-M8N
+ *
+ * Updated MODSERIAL library now compiles without errors but data seems corrupted.
+ *
+ * NMEA sentences: https://www.gpsinformation.org/dale/nmea.htm#nmea
+ *
*/
-#include "main.h"
+#include "mbed.h"
+//#include "MODSERIAL.h"
+
+//MODSERIAL pc(USBTX,USBRX);
+//MODSERIAL gps(D8, D2);
+
+Serial pc(USBTX,USBRX);
+Serial gps(D8, D2);
+
+char cDataBuffer[500];
+int i = 0;
+int h_time,m_time,s_time;
+
+void Init();
+void parse(char *cmd, int n);
+void parseTime (float timeval);
void Init()
{
- gps.baud(9600);
- pc.baud(115200);
-
+ gps.baud(115200);
+ pc.baud(115200);
pc.printf("Init OK\n");
}
@@ -47,15 +70,16 @@
}
}
-
+/*
+ * NMEA sentences: https://www.gpsinformation.org/dale/nmea.htm#nmea
+ * http://navspark.mybigcommerce.com/content/NMEA_Format_v0.1.pdf
+ */
void parse(char *cmd, int n)
-{
-
+{
char ns, ew, tf, status;
int fq, nst, fix, date; // fix quality, Number of satellites being tracked, 3D fix
float latitude, longitude, timefix, speed, altitude;
-
// Global Positioning System Fix Data
if(strncmp(cmd,"$GPGGA", 6) == 0)
{
@@ -64,27 +88,71 @@
}
// Satellite status
- if(strncmp(cmd,"$GPGSA", 6) == 0)
+ else if(strncmp(cmd,"$GPGSA", 6) == 0)
{
sscanf(cmd, "$GPGSA,%c,%d,%d", &tf, &fix, &nst);
pc.printf("GPGSA Type fix: %c, 3D fix: %d, number of sat: %d\r\n", tf, fix, nst);
}
// Geographic position, Latitude and Longitude
- if(strncmp(cmd,"$GPGLL", 6) == 0)
+ else if(strncmp(cmd,"$GPGLL", 6) == 0)
{
sscanf(cmd, "$GPGLL,%f,%c,%f,%c,%f", &latitude, &ns, &longitude, &ew, &timefix);
pc.printf("GPGLL Latitude: %f %c, Longitude: %f %c, Fix taken at: %f\n", latitude, ns, longitude, ew, timefix);
}
// Geographic position, Latitude and Longitude
- if(strncmp(cmd,"$GPRMC", 6) == 0)
+ else if(strncmp(cmd,"$GPRMC", 6) == 0)
{
sscanf(cmd, "$GPRMC,%f,%c,%f,%c,%f,%c,%f,,%d", &timefix, &status, &latitude, &ns, &longitude, &ew, &speed, &date);
pc.printf("GPRMC Fix taken at: %f, Status: %c, Latitude: %f %c, Longitude: %f %c, Speed: %f, Date: %d\n", timefix, status, latitude, ns, longitude, ew, speed, date);
}
+
+ //
+ else if(strncmp(cmd,"$GNVTG", 6) == 0)
+ {
+ // pc.printf("its a Vector Track message.\n");
+ }
+
+ else if(strncmp(cmd,"$GNGGA", 6) == 0)
+ {
+ sscanf(cmd, "$GNGGA,%f,%f,%c,%f,%c,%d,%d,%*f,%f", &timefix, &latitude, &ns, &longitude, &ew, &fq, &nst, &altitude);
+ pc.printf("GNGGA Fix taken at: %f, Latitude: %f %c, Longitude: %f %c, Fix quality: %d, Number of sat: %d, Altitude: %f M\n", timefix, latitude, ns, longitude, ew, fq, nst, altitude);
+ parseTime(timefix);
+ pc.printf("Time: %d:%d:%d\n", h_time, m_time, s_time);
+ }
+
+ else if(strncmp(cmd,"$GNGSA", 6) == 0)
+ {
+ sscanf(cmd, "$GNGSA,%c,%d,%d", &tf, &fix, &nst);
+ pc.printf("GNGSA Type fix: %c, 3D fix: %d, number of sat: %d\r\n", tf, fix, nst);
+ }
+
+ else if(strncmp(cmd,"$GPGSV", 6) == 0)
+ {
+ // pc.printf("its a Satellite details message.\n");
+ }
+
+ else if(strncmp(cmd,"$GNGLL", 6) == 0)
+ {
+ sscanf(cmd, "$GNGLL,%f,%c,%f,%c,%f", &latitude, &ns, &longitude, &ew, &timefix);
+ pc.printf("GNGLL Latitude: %f %c, Longitude: %f %c, Fix taken at: %f\n", latitude, ns, longitude, ew, timefix);
+ }
+
+ else
+ {
+ // pc.printf("Unknown message type\n");
+ }
+}
+
+void parseTime (float timeval)
+{
+ //format utc time to beijing time,add 8 time zone
+ float time = timeval + 80000.00f;
+ h_time = int(time) / 10000;
+ m_time = (int(time) % 10000) / 100;
+ s_time = int(time) % 100;
}
-
--- a/main.h Fri Aug 22 12:43:55 2014 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,19 +0,0 @@ -#pragma once -#include "mbed.h" -#include "MODSERIAL.h" - -MODSERIAL pc(USBTX,USBRX); - -#if defined(TARGET_LPC1768) -MODSERIAL gps(p13, p14); -#elif defined(TARGET_LPC4330_M4) -MODSERIAL gps(UART0_TX, UART0_RX); -#endif - - -char cDataBuffer[500]; -int i = 0; - - -void Init(); -void parse(char *cmd, int n);
--- a/mbed-src.lib Fri Aug 22 12:43:55 2014 +0000 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,1 +0,0 @@ -http://mbed.org/users/mbed_official/code/mbed-src/#ec1b66a3d094
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed.bld Thu Jul 04 04:12:41 2019 +0000 @@ -0,0 +1,1 @@ +http://mbed.org/users/mbed_official/code/mbed/builds/9baf128c2fab \ No newline at end of file