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I'm able to view my co-ords on the Serial Monitor using Serial.println(gps.location.lat(), 6);

I believe the data type returned by gps.location.lat() is double. I need to pass this value to a webservice with AT commands over GPRS.

double latitude = gps.location.lat()

Later in my code I execute AT commands to begin HTTP POST. I would like to know how to pass these double values in my paramaters.

gsm.println("AT+HTTPPARA=\"URL\",\"http://webservice/service1\""); gsm.println("AT+HTTPDATA=192,10000"); gsm.println("latitude=" + latitude); < This is not allowed.

How can I pass this parameter to my web service.

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One solution may be to split the commands:

gsm.print("latitude=");
gsm.println(latitude);

I'm not sure how you should pass multiple parameters; if it is the usual syntax you can write something like

gsm.print("latitude=");
gsm.print(latitude);
gsm.print("&longitude=");
gsm.println("longitude);

If I have the time I'll research into this a bit.

To check what is the problem, you may try to send "static" messages, like

gsm.println("latitude=12.345");

To check if this format is the correct one

EDIT: after a very quick research

It looks like the AT commands are a bit more complicated. In order to send the parameters, at least on a SIM800L, you should:

  • send the HTTPDATA command (the first parameter is the length of the payload)
  • wait for the board to send you the command DOWNLOAD
  • Send the body of the request, which is formatted as a JSON object. This means you have to send something like { "latitude" : 12.345, "longitude": 98.765 }

After all, it is much faster to use a library already developed for this, for instance ArduinoSIM800L (check a library available for your GPRS modem, or modify this one)

  • 1
    Seperating the values in individual print commands was the trick. Thanks! – Mitchel Stuart Fountaine Aug 3 '18 at 10:58

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