Emery Premeaux / Mbed 2 deprecated GPS_U-blox_NEO-M8N

GPS NMEA sentence reader for Nucleo boards.

Dependencies:   mbed MODSERIAL

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:

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.

Files at this revision

API Documentation at this revision

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

MODSERIAL.lib Show annotated file Show diff for this revision Revisions of this file
main.cpp Show annotated file Show diff for this revision Revisions of this file
main.h Show diff for this revision Revisions of this file
mbed-src.lib Show diff for this revision Revisions of this file
mbed.bld Show annotated file Show diff for this revision Revisions of this file 
diff -r acd907fbcbae -r c16325a7d225 MODSERIAL.lib
--- 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

diff -r acd907fbcbae -r c16325a7d225 main.cpp
--- 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;
 }
 
 
 
-

diff -r acd907fbcbae -r c16325a7d225 main.h
--- 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);

diff -r acd907fbcbae -r c16325a7d225 mbed-src.lib
--- 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

diff -r acd907fbcbae -r c16325a7d225 mbed.bld
--- /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