Hi there,
We are currently developing a high altitude ballon to take pictures of the Earths curvature for schools. The Arduino is cenral computer to control everything.
As part of the tracking component a GPS signal is pulled in evry so often and then sent to a ground station. This only happens whe the function is called to save energy as weight is imperative.
The problem is we keep getting the following ...
$GPGSA,A,3,09,12,14,27,29,30,31,,,,,,2.1,1.4,1.732
$GPRMC,193653.000,A,5337.7851,N,00021.7199,W,0.0,000.0,140510,,,A7A
$GP0,,,A76
$GPGSV,3,1,12,31,33,302,45,12,57,078,52,29,40,193,50,30,84,282,5171
$GPGSV,3,2,12,01,00,000,38,02,27,087,34,14,40,242,44,27,08,137,33*73
$GPGSV,3,3,12,09,12,136,30,04,17,040,31,32,06,316,,20,03,341,*77
ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ$GPGGA,193703.000,5337.7838,N,00021.7191,W,1,09,0.9,97.98,M,,,,*16
Longitude : 5337.7838,N
Latitude : 00021.7191,W
Altitude : 97.98
The ÿÿ is not aproblem in this case but sometimes it gets in the NMEA sentence like ...
$GPGGA,193713.000,5337.7776,N,00021.7196,W,1,09,0.9,ÿ96.23,M,,,,*14
Longitude : 5337.7776,N
Latitude : 00021.7196,W
Altitude : ÿ96.23
Altitude is now a false figure, this could have unexpected results at 60,000 ft up as you can imgaine.
Any idea what is going on here? what are these characters, can I get rid of them or should we just checksum the sentence and dump the odd faulty one?
Thank you for looking
#include <AikoEvents.h>
#include <string.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#define MIN_HEIGHT 1000
using namespace Aiko;
struct gpsdata {
int altitudeInt;
int longitudeInt;
int latitudeInt;
int sectorNUM;
char altitude[14];
char longitude[14];
char latitude[14];
};
int ledPin = 13; // LED test pin
int rxPin = 0; // RX PIN
int txPin = 1; // TX TX
int shutterPin = 6; // Shutter release
int runGPS = 0; // Defines if GPS Coords are to be pulled in
int intialALT = 0;
int RunOnce = 0;
int x;
int sector = 10;
void setup() {
Events.addHandler(SectorDetermine, 5000);
Events.addHandler(GetGPSCoords, sector * 1000);
Events.addHandler(takePhoto, 5000);
pinMode(ledPin, OUTPUT); // Initialize LED pin
pinMode(rxPin, INPUT);
pinMode(txPin, OUTPUT);
Serial.begin(9600);
}
static void GetGPSCoords();
static void SectorDetermine();
gpsdata data;
void loop(){
digitalWrite(ledPin, LOW);
// sector = (data.sectorNUM);
// SectorDetermine();
Events.loop();
}
static void GetGPSCoords(){
int i;
int fieldLength = 12;
int byteGPS=0;
char linea[300] ="";
char lineb[14] ="";
char comandoGPR[7] = "$GPGGA";
char comandoGPR2[7] = "$GPGSV";
char *ptr;
int cont=0;
int conta=0;
int contb=0;
int bien=1;
int indices[14];
int idxStartLong= 18;
int idxStartLat = 30;
int idxStartAlt = 41;
char delims[] = ",";
char *result = NULL;
// Serial.println("Loop Starting...");
digitalWrite(ledPin, HIGH);
byteGPS=Serial.read();
if (byteGPS == -1) {
delay(100);
}
else { // Read Byte Loop
do {
//Serial.flush();
memset(linea,0,300);
while (byteGPS != 36) {
byteGPS=Serial.read();
Serial.print(byteGPS,BYTE);
}
while (byteGPS!=13) {
linea[conta]=byteGPS;
conta++;
byteGPS=Serial.read();
Serial.print(byteGPS, BYTE);
}
conta = 0;
}
while (strncmp (linea, comandoGPR, 6) != 0);
if (byteGPS==13){ // If the received byte is = to 13, end of transmission
// Serial.println("...T E..");
digitalWrite(ledPin, LOW);
if ( strncmp(linea, comandoGPR, 6) == 0 )
{
strncpy(data.longitude,&linea[idxStartLong],(fieldLength-1));
strncpy(data.latitude,&linea[idxStartLat],fieldLength);
data.longitudeInt = atoi(data.longitude);
data.latitudeInt = atoi(data.latitude);
result = strtok( &linea[idxStartAlt], delims );
while( result != NULL ) {
if ( contb == 4 )
{
strncpy(data.altitude,result,fieldLength);
data.altitudeInt = atoi(data.altitude);
}
contb++;
result = strtok( NULL, delims );
}
}
Serial.println(""); // ... and write to the serial port
Serial.println("");
Serial.println("---------------");
Serial.print("Longitude : ");
Serial.println(data.longitude);
Serial.print("Latitude : ");
Serial.println(data.latitude);
Serial.print("Altitude : ");
Serial.println(data.altitude);
Serial.println("");
}
Serial.println("---------------");
//result = strtok( &linea[idxStartAlt], delims );
//strncpy(data.altitude,result,fieldLength);
data.altitudeInt = atoi(data.altitude);
memset(linea,0,300);
}
// Serial.println("Loop Ending....");
}
static void SectorDetermine(){
// Serial.print("Sector: " );
// Serial.print(data.sectorNUM);
// Serial.print("ALT: " );
// Serial.println(data.altitudeInt);
if ((data.altitudeInt) <= 300){
(data.sectorNUM) = 20;
// Serial.print("Sector :");
// Serial.println(data.sectorNUM);
}
if (data.altitudeInt >= 300 && data.altitudeInt <= 1500){
(data.sectorNUM) = 30;
// Serial.println(data.sectorNUM);
}
data.sectorNUM = sector;
// Serial.println(sector);
}
void takePhoto(){
digitalWrite(shutterPin, HIGH);
delay(500);
digitalWrite(shutterPin, LOW);
}
