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Topic: GPS / EM-408 Trouble (Read 2 times) previous topic - next topic


Hi there,

I purchased a EM-408 GPS Module (http://www.sparkfun.com/products/8234) and can`t make it working.
Im trying to get it running with an Arduino UNO (ATMEGA 328) and the tinyGPS Library.

The VCC is connected to 3.3V, GND to Ground, RX to Pin 0 and TX to Pin 1.
Enable/Disable is connected to 3.3V through a 4.7K Resistor and should therefore be HIGH
(my knowledge in electrics is very basic).
The Arduino receives no data from the module (RX LED is LOW).

Did anybody experience similar problems with the EM-408?

I found this: http://forum.sparkfun.com/viewtopic.php?t=6623
and this: http://geoffg.net/EM408.html
but couldn`t solve my problem.

heres the Code (its a slightly modified tinyGPS Example and compiles only with Arduino 0022)

Code: [Select]

#include <NewSoftSerial.h>
#include <TinyGPS.h>

/* This sample code demonstrates the normal use of a TinyGPS object.
   It requires the use of NewSoftSerial, and assumes that you have a
   4800-baud serial GPS device hooked up on pins 0(rx) and 1(tx).

TinyGPS gps;
NewSoftSerial nss(0, 1);

void gpsdump(TinyGPS &gps);
bool feedgps();
void printFloat(double f, int digits = 2);

void setup()
  pinMode(3, OUTPUT);
  Serial.print("Testing TinyGPS library v. "); Serial.println(TinyGPS::library_version());
  Serial.println("by Mikal Hart");
  Serial.print("Sizeof(gpsobject) = "); Serial.println(sizeof(TinyGPS));

void loop()
  bool newdata = false;
  unsigned long start = millis();
Serial.println("no Data");

  // Every 5 seconds we print an update
  while (millis() - start < 5000)
    if (feedgps())
      newdata = true;
  if (newdata)
    Serial.println("Acquired Data");

void printFloat(double number, int digits)
  // Handle negative numbers
  if (number < 0.0)
     number = -number;

  // Round correctly so that print(1.999, 2) prints as "2.00"
  double rounding = 0.5;
  for (uint8_t i=0; i<digits; ++i)
    rounding /= 10.0;
  number += rounding;

  // Extract the integer part of the number and print it
  unsigned long int_part = (unsigned long)number;
  double remainder = number - (double)int_part;

  // Print the decimal point, but only if there are digits beyond
  if (digits > 0)

  // Extract digits from the remainder one at a time
  while (digits-- > 0)
    remainder *= 10.0;
    int toPrint = int(remainder);
    remainder -= toPrint;

void gpsdump(TinyGPS &gps)
  long lat, lon;
  float flat, flon;
  unsigned long age, date, time, chars;
  int year;
  byte month, day, hour, minute, second, hundredths;
  unsigned short sentences, failed;

  gps.get_position(&lat, &lon, &age);
  Serial.print("Lat/Long(10^-5 deg): "); Serial.print(lat); Serial.print(", "); Serial.print(lon);
  Serial.print(" Fix age: "); Serial.print(age); Serial.println("ms.");
  feedgps(); // If we don't feed the gps during this long routine, we may drop characters and get checksum errors

  gps.f_get_position(&flat, &flon, &age);
  Serial.print("Lat/Long(float): "); printFloat(flat, 5); Serial.print(", "); printFloat(flon, 5);
  Serial.print(" Fix age: "); Serial.print(age); Serial.println("ms.");


  gps.get_datetime(&date, &time, &age);
  Serial.print("Date(ddmmyy): "); Serial.print(date); Serial.print(" Time(hhmmsscc): "); Serial.print(time);
  Serial.print(" Fix age: "); Serial.print(age); Serial.println("ms.");


  gps.crack_datetime(&year, &month, &day, &hour, &minute, &second, &hundredths, &age);
  Serial.print("Date: "); Serial.print(static_cast<int>(month)); Serial.print("/"); Serial.print(static_cast<int>(day)); Serial.print("/"); Serial.print(year);
  Serial.print("  Time: "); Serial.print(static_cast<int>(hour)); Serial.print(":"); Serial.print(static_cast<int>(minute)); Serial.print(":"); Serial.print(static_cast<int>(second)); Serial.print("."); Serial.print(static_cast<int>(hundredths));
  Serial.print("  Fix age: ");  Serial.print(age); Serial.println("ms.");

  Serial.print("Alt(cm): "); Serial.print(gps.altitude()); Serial.print(" Course(10^-2 deg): "); Serial.print(gps.course()); Serial.print(" Speed(10^-2 knots): "); Serial.println(gps.speed());
  Serial.print("Alt(float): "); printFloat(gps.f_altitude()); Serial.print(" Course(float): "); printFloat(gps.f_course()); Serial.println();
  Serial.print("Speed(knots): "); printFloat(gps.f_speed_knots()); Serial.print(" (mph): ");  printFloat(gps.f_speed_mph());
  Serial.print(" (mps): "); printFloat(gps.f_speed_mps()); Serial.print(" (kmph): "); printFloat(gps.f_speed_kmph()); Serial.println();


  gps.stats(&chars, &sentences, &failed);
  Serial.print("Stats: characters: "); Serial.print(chars); Serial.print(" sentences: "); Serial.print(sentences); Serial.print(" failed checksum: "); Serial.println(failed);
bool feedgps()
  while (nss.available())
    if (gps.encode(nss.read()))
      return true;
  return false;

Thanks for any answers



You can't use D0 and D1 for NewSoftSerial if you are using them for Serial.  Try moving the GPS to other pins, like D2 and D3.
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Hi johnwasser,

thanks for the reply.
I changed the pins, still no data is send to the arduino.
The module should send data immediately after it started up right?


The module should send data immediately after it started up right?

No. The data sheet says that it takes an average of 42 seconds to cold start.

Are you doing this:
RX: This is the main receive channel for receiving software commands to the engine board from
SiRfDemo software or from user-written software. (NOTE: When not in use this pin must be
kept "HIGH" for operation. From Vcc connect a 470 Ohm resistor in series with a 3.2v Zener
diode to Ground. Then, connect the Rx input to Zener's cathode to pull the input "HIGH".)


Your Rx and Tx lines are backwards.  You need to connect the Tx pin on the GPS to the Rx pin on the Arduino and vice versa.
I2C GPS Shield

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