Ultimate GPS shield can't run on more than 1hz with MEGA

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thegunman
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by thegunman »

what is this refference for?

Do I realy need it?

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adafruit_support_rick
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by adafruit_support_rick »

No, you don't need it. But you've declared that you're using it, so you have to supply it. Take out that line of code if you don't want to have an external voltage reference.

thegunman
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by thegunman »

I tested it without that and it works

I may be a bit annoying but I want to understand what does what, not someone to do it and next time again to ask same questions

Thank you!

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adafruit_support_rick
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by adafruit_support_rick »

The analog reference is what your analog input is compared against. The default on the Mega is an internal 5V reference, but you can supply an external reference like 3.3V by connecting it to the AREF pin.

http://arduino.cc/en/Reference/AnalogReference

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dianesk8
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by dianesk8 »

I am simply trying to use Hardware Serial on the Mega to read the Ultimate GPS. I used the code shared below by Rick in a much earlier post.
I get this reading from the GPS,
Time: 0:0:0.0
Date: 0/0/200
Fix: 0 quality: 0

I have had it working with Software Serial for a while. It is powered through the Mega, and connected to Serial1 pins 18 and 19 (tried both ways).
Please help me figure out what I am missing in reading the GPS thorugh Hardware serial - is it a library?
thanks

Code: Select all

// Test code for Adafruit GPS modules using MTK3329/MTK3339 driver
//
// This code shows how to listen to the GPS module in an interrupt
// which allows the program to have more 'freedom' - just parse
// when a new NMEA sentence is available! Then access data when
// desired.
//
// Tested and works great with the Adafruit Ultimate GPS module
// using MTK33x9 chipset
//    ------> http://www.adafruit.com/products/746
// Pick one up today at the Adafruit electronics shop 
// and help support open source hardware & software! -ada

#include <Adafruit_GPS.h>
#include <SoftwareSerial.h>

// If you're using a GPS module:
// Connect the GPS Power pin to 5V
// Connect the GPS Ground pin to ground
// If using software serial (sketch example default):
//   Connect the GPS TX (transmit) pin to Digital 3
//   Connect the GPS RX (receive) pin to Digital 2
// If using hardware serial (e.g. Arduino Mega):
//   Connect the GPS TX (transmit) pin to Arduino RX1, RX2 or RX3
//   Connect the GPS RX (receive) pin to matching TX1, TX2 or TX3

// If you're using the Adafruit GPS shield, change 
// SoftwareSerial mySerial(3, 2); -> SoftwareSerial mySerial(8, 7);
// and make sure the switch is set to SoftSerial

// If using software serial, keep these lines enabled
// (you can change the pin numbers to match your wiring):
//SoftwareSerial mySerial(8, 7);

#define mySerial Serial1

Adafruit_GPS GPS(&mySerial);
// If using hardware serial (e.g. Arduino Mega), comment
// out the above six lines and enable this line instead:
//Adafruit_GPS GPS(&Serial1);


// Set GPSECHO to 'false' to turn off echoing the GPS data to the Serial console
// Set to 'true' if you want to debug and listen to the raw GPS sentences. 
#define GPSECHO  true

// this keeps track of whether we're using the interrupt
// off by default!
boolean usingInterrupt = false;
void useInterrupt(boolean); // Func prototype keeps Arduino 0023 happy

void setup()  
{
    
  // connect at 115200 so we can read the GPS fast enough and echo without dropping chars
  // also spit it out
  Serial.begin(115200);
  Serial.println("Adafruit GPS library basic test!");

  // 9600 NMEA is the default baud rate for Adafruit MTK GPS's- some use 4800
  GPS.begin(9600);
  GPS.sendCommand("$PMTK251,19200*22");  //set baud rate to 19200
//  GPS.sendCommand("$PMTK251,9600*17");  //set baud rate to 9600
  mySerial.end();
  GPS.begin(19200);
  
  // uncomment this line to turn on RMC (recommended minimum) and GGA (fix data) including altitude
  GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCGGA);
  // uncomment this line to turn on only the "minimum recommended" data
  //GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCONLY);
  // For parsing data, we don't suggest using anything but either RMC only or RMC+GGA since
  // the parser doesn't care about other sentences at this time
  
  // Set the update rate
  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_10HZ);   // 1 Hz update rate
  // For the parsing code to work nicely and have time to sort thru the data, and
  // print it out we don't suggest using anything higher than 1 Hz

  // Request updates on antenna status, comment out to keep quiet
  GPS.sendCommand(PGCMD_NOANTENNA);

  // the nice thing about this code is you can have a timer0 interrupt go off
  // every 1 millisecond, and read data from the GPS for you. that makes the
  // loop code a heck of a lot easier!
  useInterrupt(true);

  delay(1000);
  // Ask for firmware version
  GPS.sendCommand(PMTK_Q_RELEASE);
}


// Interrupt is called once a millisecond, looks for any new GPS data, and stores it
SIGNAL(TIMER0_COMPA_vect) {
  char c;
 
  while (mySerial.available())
  {
    c = GPS.read();
    // if you want to debug, this is a good time to do it!
    if (GPSECHO)
    #ifdef UDR0
      if (c) UDR0 = c;  
      // writing direct to UDR0 is much much faster than Serial.print 
      // but only one character can be written at a time.
    #else
      if (c) Serial.write(c);
    #endif
  }
}

void useInterrupt(boolean v) {
  if (v) {
    // Timer0 is already used for millis() - we'll just interrupt somewhere
    // in the middle and call the "Compare A" function above
    OCR0A = 0xAF;
    TIMSK0 |= _BV(OCIE0A);
    usingInterrupt = true;
  } else {
    // do not call the interrupt function COMPA anymore
    TIMSK0 &= ~_BV(OCIE0A);
    usingInterrupt = false;
  }
}

uint32_t timer = millis();
void loop()                     // run over and over again
{
  // in case you are not using the interrupt above, you'll
  // need to 'hand query' the GPS, not suggested :(
  if (! usingInterrupt) {
    // read data from the GPS in the 'main loop'
    while (mySerial.available())
    {
      char c = GPS.read();
      // if you want to debug, this is a good time to do it!
      if (GPSECHO)
        if (c) Serial.write(c);
    }
  }  
  
  // if a sentence is received, we can check the checksum, parse it...
  if (GPS.newNMEAreceived()) {
    // a tricky thing here is if we print the NMEA sentence, or data
    // we end up not listening and catching other sentences! 
    // so be very wary if using OUTPUT_ALLDATA and trytng to print out data
    //Serial.println(GPS.lastNMEA());   // this also sets the newNMEAreceived() flag to false
  
    if (!GPS.parse(GPS.lastNMEA()))   // this also sets the newNMEAreceived() flag to false
      return;  // we can fail to parse a sentence in which case we should just wait for another
  }

  // if millis() or timer wraps around, we'll just reset it
  if (timer > millis())  timer = millis();

  // approximately every 2 seconds or so, print out the current stats
  if (millis() - timer > 2000) { 
    timer = millis(); // reset the timer
    
    Serial.print("\nTime: ");
    Serial.print(GPS.hour, DEC); Serial.print(':');
    Serial.print(GPS.minute, DEC); Serial.print(':');
    Serial.print(GPS.seconds, DEC); Serial.print('.');
    Serial.println(GPS.milliseconds);
    Serial.print("Date: ");
    Serial.print(GPS.day, DEC); Serial.print('/');
    Serial.print(GPS.month, DEC); Serial.print("/20");
    Serial.println(GPS.year, DEC);
    Serial.print("Fix: "); Serial.print((int)GPS.fix);
    Serial.print(" quality: "); Serial.println((int)GPS.fixquality); 
    if (GPS.fix) {
      Serial.print("Location: ");
      Serial.print(GPS.latitude, 4); Serial.print(GPS.lat);
      Serial.print(", "); 
      Serial.print(GPS.longitude, 4); Serial.println(GPS.lon);
      
      Serial.print("Speed (knots): "); Serial.println(GPS.speed);
      Serial.print("Angle: "); Serial.println(GPS.angle);
      Serial.print("Altitude: "); Serial.println(GPS.altitude);
      Serial.print("Satellites: "); Serial.println((int)GPS.satellites);
    }
  }
}

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adafruit_support_rick
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by adafruit_support_rick »

Code: Select all

  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_10HZ);   // 1 Hz update rate
Hmmm...Does it work at 1Hz or at 5Hz?

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dianesk8
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by dianesk8 »

I had the Software serial working at 1 Hz using the "parsing" sample code and pins 3,2. This was causing me interference problems with the servos on pins 8 and 9 (PWM). So I got the Adafruit servo shield and got rid of the interference problem, but I really don't need that shield for anything else and I'd prefer a different one with built-in connectors. I read on one of these forums that someone solved a similar problem by using Hardware serial. That should be fairly straightforward on the Mega but I can't seem to get a reading.
thanks for your thoughts

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adafruit_support_rick
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by adafruit_support_rick »

I was wondering of hardware serial works at 1 or 5Hz. Trying to narrow down the problem you're seeing...

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dianesk8
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by dianesk8 »

Using Software Serial on the Mega thru pins 53,52 (not 3,2 as on the Uno), the example code "parsing" works, and updates data once every 2 or 3 sec. My own code works in this fashion as well.

I fixed the line of code to set the update rate to 1Hz

Code: Select all

  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ);   // 1 Hz update rate

It did not affect the performance.
When I try the code with Hardware Serial, the Serial monitor updated about once every 1.5 sec., but only gave me the 0 readings for Time, Date and Fix. I am using Mega pins 18, 19 for GPS Tx and Rx respectively.
I must be missing something obvious.
thanks for your help

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Franklin97355
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by Franklin97355 »

I am simply trying to use Hardware Serial on the Mega
The code you attached is not set up for hardware serial.

Code: Select all

// If you're using the Adafruit GPS shield, change 
// SoftwareSerial mySerial(3, 2); -> SoftwareSerial mySerial(8, 7);
// and make sure the switch is set to SoftSerial

// If using software serial, keep these lines enabled
// (you can change the pin numbers to match your wiring):
//SoftwareSerial mySerial(8, 7);

#define mySerial Serial1

Adafruit_GPS GPS(&mySerial);
// If using hardware serial (e.g. Arduino Mega), comment
// out the above six lines and enable this line instead:
//Adafruit_GPS GPS(&Serial1);

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dianesk8
 
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Re: Ultimate GPS shield can't run on more than 1hz with MEGA

Post by dianesk8 »

Fairly dumb mistake that is now fixed by making more secure connections to the pins on the Mega. I realized that the 0 data meant I wasn't hooked up correctly to the GPS (the Tx to Rx and vice versa confused me).
Thanks for looking into it - I now have data coming in from Serial port and it does not interfere with the Servos!

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