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Drivers Manual

Network - NMEA Position and Heading (CheckSum) - 12


  • Position data
    The driver will automatically detect the position format from the first NMEA position sentence supported.
    Driver will decode following NMEA sentences, containing (GPS or RTK) position data:
    • $--GGA,
    • $--RMC,
    • $--GGK, or
    • $--GLL
  • Quality
    Driver can be used to decode quality information from NMEA sentences.
    It will automatically decode the supported NMEA quality sentences and copy the values to the previously decoded position data buffer.
    The driver decodes:
    • $--GST,
    • $--GSA
    • $PDAS,QUAL,
  • Heading
    Driver will automatically detect the heading format from the first NMEA gyro string.
    The driver is able to decode heading from NMEA sentences:
    • $--HDT,
    • $--HDG,
    • $--HDM
  • Communication
    The driver does not actively communicate with the positioning system; it listens to the incoming messages.
    Two communication versions of the driver are available, but the internal workings of the drivers are the same except for the data reception:
    • Serial
    • Network version (UDP).
  • Timing
    The time tag of (all) the data is determined from the position sentence, i.e. the time tag of the (first) heading (after the position data) is copied from the position buffer update time.
    However, the data buffers are not updated until the last sentence from an NMEA block is received. NMEA blocks are determined as follows:
  • Auto-Detection of NMEA Formats
    1. After starting up, or after a "Reset I/O" command has been issued by the Qinsy Controller, the driver waits for the first NMEA position sentence that can be properly decoded.
      The NMEA type of this sentence will determine the next NMEA position sentences that are decoded.
    2. All NMEA quality information sentences and NMEA gyro compass sentences that are received before the second NMEA position sentence will be considered to be part of one NMEA block.
    3. The format of the last NMEA quality information sentence or NMEA gyro compass sentence will be used to define the NMEA sentence that will trigger an update of the driver data buffers.
      There is a command line option to disregard gyro compass sentences as trigger strings.
    4. If only NMEA position sentences are received (during the auto-detection phase), then the driver position data buffer is updated for each valid NMEA position sentence of the right format.
    5. Be aware that the auto-detection process will take at least two valid position sentences (twice the position update cycle time) after starting up the driver.
    6. The auto-detection process will be restarted after each "Reset I/O" command.
  • Warnings

    Update Rates
    This driver can be used when an NMEA position, NMEA quality sentence(s) and NMEA heading are received on the same port and at the same update rate
    If the gyro is updating faster than the positions, then the data have to be split and separate position and gyro systems have to be defined on separate ports.
    The driver also assumes that the position sentence is output first, before quality and gyro heading.