Delay() interferes with NMEA sentence? [Resolved]

Getting Started
1

I was having a great deal of difficulty getting a GPS fix from my AssetTracker Shield. NMEA sentence was garbled and gpsFix() returned false, even though red LED on the AssetTracker was off (indicating a valid GPS fix).
I finally resolved the issue by deleting delay(1000) statement from the application.
I surmise that the delay() function interferes with serial communication between the GPS module and the Adafruit parser.
Does anyone know whether this makes sense?

2

I’d go with yes, it make sense that that would happen.

Reading the serial data from the GPS occurs in the main loop(), so if you block the loop by using a delay() it’s quite likely that data would be lost.

3

Thanks rickkas7. That helps.

4

Thanks for the help @rickkas7

5

OK, so I got rid of the delay() statements, and substituted a simple test to determine whether I have a good fix. I’m still puzzled by how it (doesn’t) work. Following is my test program

#include "AssetTracker/AssetTracker.h"
long lastPrint = 0;
AssetTracker t = AssetTracker();
void setup() {
    t.begin();
    t.gpsOn();
    Serial.begin(9600);
}
void loop() {
    t.updateGPS();
    if(t.gpsFix())
    if(millis()-lastPrint > 6000){
        lastPrint = millis();
        Serial.println(t.preNMEA());
        }
    }

and a portion of the output it generates.

 6,3
$GPGGA,151145.000,4429.6503,N,06348.3967,W,1,10,0.83,27.1,M,-23.7,M,,*6S,02,3
$GPGGA,151152.000,4429.6503,N,06348.3967,W,1,10,0.83,27.1,M,-23.7,M,,*6S,02,3
$GPGGA,151152.000,4429.6503,N,06348.3967,W,1,10,0.83,27.1,M,-23.7,M,,*6S,02,3
$,,210*C0.6,96
$GPGGA,151208.000,4429.6500,N,06348.3964,W,1,10,0.83,27.1,M,,S,,2,3
$GPGGA,151211.000,4429.6498,N,06348.3964,W,1,10,0.83,27.1,M,-23.7,M,,*6S108,,.03
$GPGGA,151227.000,4429.6498,N,06348.3959,W,2,10,0.83,27.1,M,-23.7,M,000,02237G230634
$GPGGA,151227.000,4429.6498,N,06348.3959,W,2,10,0.83,27.1,M,-23.7,M,000,02237G230634

I seem to be having difficulty getting consistent transmissions of the NMEA sentence from the Adafruit GPS to the Electron.

Notice that the time difference between subsequent fixes is not always 6 seconds.

Any suggestions?

6

I’m not a huge fan of the Adafruit GPS library. I prefer the TinyGPS++ library which I find to be more reliable. This is a Particle port of the TinyGPS++ library, plus my LIS3DH driver, with an optional compatibility layer so the API is mostly the same as the official AssetTracker library.

3 Likes
7

Thanks rickkas7, I will give it a try. :wink:

1 Like