itead GPS shield data


I received the itead gps shield the other day and I have it receiving data, but for some reason it will not form a valid sentence. I am using the tinygps library, and just some test code I found in another thread. I went for a drive and stuck the antenna on the top of my car so it had no object interference, and I got accurate results in terms of lat and long but it looks like the last few fields of the sentence are not coming in properly. Here is a sample of the data I am receiving:

$GPRMC,183358.00,A,XX09.82329,N,08631.94267,W,20.033,181.88,2714 CHARS=15220 SENTENCES=0 CSUM ERR=0
$GPRMC,183359.00,A,XX09.81761,N,08631.94287,W,20.604,181.48,271, CHARS=15284 SENTENCES=0 CSUM ERR=0
$GPRMC,183400.00,A,XX09.81178,N,08631.94295,W,21.227,180.40,271S CHARS=15348 SENTENCES=0 CSUM ERR=0
$GPRMC,183401.00,A,XX09.80578,N,08631.94296,W,21.717,179.99,2713 CHARS=15412 SENTENCES=0 CSUM ERR=0
~3 min interval
$GPRMC,183725.00,A,XX09.63394,N,08632.14179,W,0.037,271013,D, CHARS=28555 SENTENCES=0 CSUM ERR=2
$GPRMC,183726.00,A,XX09.63393,N,08632.14179,W,0.018,271013,D.7 CHARS=28620 SENTENCES=0 CSUM ERR=2
$GPRMC,183727.00,A,XX09.63392,N,08632.14178,W,0.010,271013,D0 CHARS=28684 SENTENCES=0 CSUM ERR=2
$GPRMC,183728.00,A,XX09.63391,N,08632.14178,W,0.002,271013,DE4 CHARS=28749 SENTENCES=0 CSUM ERR=2

Using this code:

#include <SoftwareSerial.h>

#include <TinyGPS.h>

/* This sample code demonstrates the normal use of a TinyGPS object.
   It requires the use of SoftwareSerial, and assumes that you have a
   4800-baud serial GPS device hooked up on pins 3(rx) and 4(tx).

TinyGPS gps;
SoftwareSerial ss(3, 4);

void setup()
  Serial.print("Simple TinyGPS library v. "); Serial.println(TinyGPS::library_version());
  Serial.println("by Mikal Hart");

void loop()
  bool newData = false;
  unsigned long chars;
  unsigned short sentences, failed;

  // For one second we parse GPS data and report some key values
  for (unsigned long start = millis(); millis() - start < 1000;)
    while (ss.available())
      char c =;
      Serial.write(c); // uncomment this line if you want to see the GPS data flowing
      if (gps.encode(c)) // Did a new valid sentence come in?
        newData = true;

  if (newData)
    float flat, flon;
    unsigned long age;
    gps.f_get_position(&flat, &flon, &age);
    Serial.print(flat == TinyGPS::GPS_INVALID_F_ANGLE ? 0.0 : flat, 6);
    Serial.print(" LON=");
    Serial.print(flon == TinyGPS::GPS_INVALID_F_ANGLE ? 0.0 : flon, 6);
    Serial.print(" SAT=");
    Serial.print(gps.satellites() == TinyGPS::GPS_INVALID_SATELLITES ? 0 : gps.satellites());
    Serial.print(" PREC=");
    Serial.print(gps.hdop() == TinyGPS::GPS_INVALID_HDOP ? 0 : gps.hdop());
  gps.stats(&chars, &sentences, &failed);
  Serial.print(" CHARS=");
  Serial.print(" SENTENCES=");
  Serial.print(" CSUM ERR=");

Any advice on how to get a valid sentence so that it can be parsed? I was thinking about trying to change the library to ignore some of the fields since I don’t need them. I am only interested in long, lat, time, and speed over ground for the application.

Thanks for any advice!

There's another thread on the same topic:

The consensus so far is that that shield doesn't emit the checksum as tinyGPS expects - there is no asterisk in the data to mark the checksum.

Thanks, in all of my searching I somehow did not come across that thread. So recommendation seems to be modify the library to ignore the checksum?

Or write something to parse out what you need.