Add GPVTG sentence process

main.c

@@ -104,6 +104,28 @@ void nmea_sentence_process(const char *nmea_sentence)
         }
       }
      }
+    else if (strncmp(nmea_sentence + 1, "GPVTG", 5) == 0)  // Process GPVTG sentence
+    {
+     for (i = 7; nmea_sentence[i] != '\0'; i++)
+     {
+     if (nmea_sentence[i] == ',')
+       {
+       if (field_number == 6)
+           {
+              speed_kmh = atof(nmea_sentence + i - field_index);
+              control_leds_based_on_speed(speed_kmh);
+           }
+              field_number++;
+              field_index = 0;
+                }
+     else if (nmea_sentence[i] == '*')
+          {
+           break;
+          }
+     else {
+           field_index++;
+          }
+         }
 }