GNSS Receivers

NexNav GNSS

Once the device hardware installation explained in the NexNav GNSS - Integration examples section of the 1x Hardware Manual has been completed, follow the steps below to perform the proper software installation.

The following steps explain how to configure Veronte Autopilot 1x to integrate NexNav as an external GNSS sensor via RS232:

  1. Go to Input/Output menu \(\rightarrow\) Serial panel \(\rightarrow\) RS232 tab.

    Configure the serial port parameters:

    • Baudrate: 19200

    • Length: 8

    • Stop: 1

    • Parity: Disabled

    ../../_images/nexnav_baudrate.png

    NexNav GNSS - RS232 configuration

  2. Go to Input/Output menu \(\rightarrow\) I/O Setup panel \(\rightarrow\) Configuration tab.

    Connect the RS232 producer to a RS custom message consumer, in this example RS custom message 1 is used:

    ../../_images/nexnav_config_rs232_custom.png

    NexNav GNSS - RS232 \(\rightarrow\) RS custom message 1

  3. Click on gears to configure the RS custom message 1 consumer to store the information received from the external GNSS. Users must setup it by defining the protocol specified by the manufacturer:

    ../../_images/nexnav_custom_message.png

    NexNav GNSS - RS custom message 1 configuration

    For both messages:

    • Endianness: Big endian

    • Time out: 3 seconds

    • Time to Idle: 0.005 seconds

    • Bit ID:

      • For message 00 \(\Rightarrow\) “Custom msg 0 Rx Error” renamed to Navigation Data

      • For message 01 \(\Rightarrow\) “Custom msg 1 Rx Error” renamed to Auxiliar Navigation Data

  4. Then, to configure each message, access its configuration edit_list:

    (00) - Navigation Data Message

    Byte

    Parameter

    Custom message type

    Message configuration

    0

    Matcher x10

    Matcher

    • Value: 16

    • Bits: 8

    • Mask: 255

    1

    Matcher x51

    Matcher

    • Value: 81

    • Bits: 8

    • Mask: 255

    2

    Nav State

    (Real Variable, 32 bits)

    Variable

    • Compression: Compress - Bits Unsigned

    • Bits: 8

    • Encode - Min/Max: 0.0/1.0

    • Decode - Min/Max: 0/1

    3-4

    Data Validity Flags

    (Real Variable, 32 bits)

    Variable

    • Compression: Compress - Bits Unsigned

    • Bits: 16

    • Encode - Min/Max: 0.0/1.0

    • Decode - Min/Max: 0/1

    5-8

    Time of Fix

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    9-32

    External GNSS Position

    (Feature Variable, 192 bits)

    Position

    • Units: Radians

    • Factor: 1.0

    33-36

    UTC Time

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    37-38

    Skip 16

    Skip

    Bits: 16

    39-42

    GPS North Velocity

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    43-46

    GPS East Velocity

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    47-50

    GPS Vertical Velocity

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    51-62

    Skip 96

    Skip

    Bits: 96

    63-66

    HFOM

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    67-78

    Skip 96

    Skip

    Bits: 96

    79-82

    VFOM

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    83-88

    Skip 48

    Skip

    Bits: 48

    89

    Matcher x10

    Matcher

    • Value: 16

    • Bits: 8

    • Mask: 255

    90

    Matcher x3

    Matcher

    • Value: 3

    • Bits: 8

    • Mask: 255

    (01) - Auxiliary Navigation Data Message

    Byte

    Parameter

    Custom message type

    Message configuration

    0

    Matcher x10

    Matcher

    • Value: 16

    • Bits: 8

    • Mask: 255

    1

    Matcher x80

    Matcher

    • Value: 128

    • Bits: 8

    • Mask: 255

    2

    Data Validity Flags Auxiliar

    (Real Variable, 32 bits)

    Variable

    • Compression: Compress - Bits Unsigned

    • Bits: 8

    • Encode - Min/Max: 0.0/1.0

    • Decode - Min/Max: 0/1

    3-6

    VHFOM

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    7-10

    VVFOM

    (Real Variable, 32 bits)

    Variable

    • Compression: Uncompress

    • Encode/Decode: 1.0

    11-22

    Skip 96

    Skip

    Bits: 96

    23-24

    HDOP

    (Real Variable, 32 bits)

    Variable

    • Compression: Compress - Bits Unsigned

    • Bits: 16

    • Encode - Min/Max: 0.0/1.0

    • Decode - Min/Max: 0/100

    25-26

    VDOP

    (Real Variable, 32 bits)

    Variable

    • Compression: Compress - Bits Unsigned

    • Bits: 16

    • Encode - Min/Max: 0.0/1.0

    • Decode - Min/Max: 0/100

    27-28

    PDOP

    (Real Variable, 32 bits)

    Variable

    • Compression: Compress - Bits Unsigned

    • Bits: 16

    • Encode - Min/Max: 0.0/1.0

    • Decode - Min/Max: 0/100

    29-31

    Skip 24

    Skip

    Bits: 24

    32

    Matcher x10

    Matcher

    • Value: 16

    • Bits: 8

    • Mask: 255

    33

    Matcher x3

    Matcher

    • Value: 3

    • Bits: 8

    • Mask: 255

    Important

    All user variables used in these messages have been previously renamed in the Variables panel of the UI menu.

  5. Go to Block Programs menu and create a new program, in this example this program is renamed to NexNav.

    The following program is defined to check that the information coming from the external GNSS is valid and can be used as an input of the Navigation block:

    ../../_images/nexnav_new_program.png

    NexNav GNSS - NexNav block program

    Important

    Navigation Data is the bit that has been previously assigned to the CAN custom message “Navigation Data Message” to check that it is received correctly.

  6. Go to Block Programs menu \(\rightarrow\) Navigation program.

    Note

    Usually the user has a Navigation program where the navigation blocks are implemented. However, the user can name the program as desired.

    • Add a GNSS sensor block, set it as a GPS External and configure it as follows:

      ../../_images/nexnav_gnss_external_1.png

      GPS External block configuration - Configuration tab


      • Enable

        Period: 0.2 s

      • Fix Bit: User BIT 05 Error, renamed to “Fix Bit GNSS”.

        This bit is written on the NexNav program detailed above

      • Time of Week: UTC Time

        (real user variable received from the sensor)

      • GPS Week: Value 0

        (real user variable previously renamed and defined with an init value of 0)

        white

      • GPS Position: External GNSS Position (feature user variable received from the sensor)

      • Horizontal Position Error: 2 m

      • Vertical Position Error: 5 m


      • Horizontal Velocity Error: 0.4 m/s

      • Vertical Velocity Error: 0.4 m/s

      • Velocity North: GPS North Velocity (real user variable received from the sensor)

      • Velocity East: GPS East Velocity (real user variable received from the sensor)

      • Velocity Down: GPS Vertical Velocity (real user variable received from the sensor)


      ../../_images/nexnav_gnss_external_2.png

      GPS External block configuration - Sensor Variance tab


      • Horizontal Position

        \(\Rightarrow\) Use receiver value if present: Enabled

        white

      • Vertical Position

        \(\Rightarrow\) Square error: 20.0 \(m^2\)

        white

      • Horizontal Velocity

        \(\Rightarrow\) Use receiver value if present: Enabled

        white

      • Vertical Velocity

        \(\Rightarrow\) Square error: 2.0 \((m/s)^2\)

        white

      • Relative Position

        \(\Rightarrow\) Square error: 5.0 \(m^2\)





      For more information on this block, see GNSS sensor block - Block Programs section of this manual.

    • Add 2 EKF adapter blocks to be able to use the sensor information in the calculation of the navigation algorithm, Position EKF adapter block and Velocity EKF adapter block.

      And, connect the outputs of the GNSS external block to the correspondings inputs of these blocks, as shown below:

      ../../_images/nexnav_gnss_external_block.png

      NexNav GNSS - Position and Velocity EKF adapter blocks

    • Finally, the outputs of these 2 blocks must be inputs to the Navigation block.

    The complete setup should look like this:

    ../../_images/nexnav_navigation_program.png

    NexNav GNSS - Navigation program