GPS

The SAM-M8Q GNSS module is a concurrent GNSS receiver which can receive and track multiple GNSS systems: GPS, Galileo and GLONASS. Owing to the dual-frequency RF front-end architecture, GLONASS can be processed concurrently with GPS and Galileo signals, thus providing reception of three GNSS systems. By default, the M8 receivers are configured for concurrent GPS and GLONASS, including SBAS and QZSS reception. If power consumption is a key factor, then the receiver should be configured for a single GNSS operation using GPS, Galileo or GLONASS and disabling QZSS and SBAS. The module can also be configured to receive any single GNSS constellation.

u-center

u-center is GNSS evaluation software for Windows.

Highlights

• Highly interactive and easy to use.
• Full support of all u‑blox GNSS receivers.
• Extensive configuration and control features.
• Real‑time display from a GNSS receiver via RS232 and USB interface.

With the tool u-center from u-blox you can play around

Sketch

/*
  MIT License

  Copyright (c) 2018 GabrielNotman

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
 */

#define WIRE_BUS 1
#define SERIAL_BUS 2

#define GPS_INTERFACE WIRE_BUS 

#if (GPS_INTERFACE == WIRE_BUS)
  #include <Wire.h>
  #define GPS_STREAM Wire
  #define GPS_ADR 0x42
#elif (GPS_INTERFACE == SERIAL_BUS)
  #define GPS_STREAM Serial
  #define GPS_BAUD 57600
#else
  #error "Invalid GPS_INTERFACE"
#endif

#define CONSOLE_STREAM SerialUSB
#define CONSOLE_BAUD 9600

#define READ_TIMEOUT_MS 100

#define BUFFER_SIZE 256
uint8_t buffer[BUFFER_SIZE];

void setup()
{
  gpsEnable(true);

#if (GPS_INTERFACE == WIRE_BUS)
  Wire.begin();
#elif (GPS_INTERFACE == SERIAL_BUS)
  GPS_STREAM.begin(GPS_BAUD);
#endif

  CONSOLE_STREAM.begin(CONSOLE_BAUD);
}

void loop() 
{
  //Console -> GPS
  memset(buffer, 0, BUFFER_SIZE);
  writeGPS(readConsole());

  //GPS -> Console
  memset(buffer, 0, BUFFER_SIZE);
  writeConsole(readGPS());
}

void gpsEnable(bool state)
{
  //Enable GPS module
  pinMode(GPS_ENABLE, OUTPUT);
  digitalWrite(GPS_ENABLE, state);
}

size_t readGPS()
{
#if (GPS_INTERFACE == WIRE_BUS)
  return readUbloxI2cStream();
#elif (GPS_INTERFACE == SERIAL_BUS)
  return readSerialStream((Stream*)&GPS_STREAM);
#endif
}

size_t readConsole() 
{
  return readSerialStream((Stream*)&CONSOLE_STREAM);
}

#if (GPS_INTERFACE == WIRE_BUS)
size_t readUbloxI2cStream()
{
  uint16_t count = 0;
  Wire.beginTransmission(GPS_ADR);
  Wire.write((uint8_t)0xFD);
  Wire.endTransmission(false);
  Wire.requestFrom(GPS_ADR, 2);
  count = (uint16_t)(Wire.read() << 8) | Wire.read();
  count = (count > BUFFER_SIZE) ? BUFFER_SIZE : count;

  if (count) {
    for (size_t i = 0; i < (count-1); i++) {
      Wire.requestFrom(GPS_ADR, 1, false);
      buffer[i] = Wire.read();
    }
    Wire.requestFrom(GPS_ADR, 1);
    buffer[count-1] = Wire.read();
  }

  return count;
}
#endif

size_t readSerialStream(Stream* stream) 
{
  uint32_t last = millis();
  size_t count = 0;
  while ((count < BUFFER_SIZE) && (millis() < (last + READ_TIMEOUT_MS))) {
    if (stream->available()) {
      buffer[count++] = stream->read();
      last = millis();
    }
  }
  return count;  
}

void writeGPS(size_t count)
{
#if (GPS_INTERFACE == WIRE_BUS)
  Wire.beginTransmission(GPS_ADR);
  Wire.write(buffer, count);
  Wire.endTransmission();
#elif (GPS_INTERFACE == SERIAL_BUS)
  for (size_t i = 0; i < count; i++) {
    GPS_STREAM.write(buffer[i]);
  }
#endif
}

void writeConsole(size_t count)
{
  for (size_t i = 0; i < count; i++) {
    CONSOLE_STREAM.write(buffer[i]);
  }
}