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User Guide: simpleRTK3B Heading

Product Overview

You can use simpleRTK3B Heading as a standalone board by connecting it to your PC or tablet. Additionally, it can be used as an add-on board for your projects, such as an Arduino shield. The main component of simpleRTK3B Heading is Mosaic-H multi band (L1, L2 and E5b) RTK GNSS module.
Important before use:
This is a traditional RTK module, it only finds satellites outdoors. If you try to use it next to the Window it will not find any satellites. The module needs 10 seconds to boot, be patient after connecting to the PC 🙂

Hardware

Pinout definition

Power

mosaic_H-Power
The simpleRTK3B Heading can be powered from 4 different sources:
  • GPS USB port
  • XBEE USB port
  • Pixhawk connector
  • Arduino rail
Only 1 of them is needed to use the board, but you can also connect the 4 at the same time, there’s no risk.
The simpleRTK3B Heading has a High Power (HP) XBee socket. You can connect any XBee accessory to it. If you connect a device that requires high power to the XBee socket, you will have to make sure your power supply can provide this power.
  • Use only high quality USB-C cables, not longer than 1 meter.
  • If you connect simpleRTK3B Heading through a USB hub to your PC/Tablet or your PC has low power USB ports, you will have to connect the second USB port directly to a wall plug or high power USB port.

Communication ports

simpleRTK3B Heading board has a few interfaces that we will now explain in detail.

USB GPS
mosaicH_USB-GPS
This USB-C connector gives you access to the native USB from the Mosaic module. When you connect to the PC for the first time, you will only see a new Hard Disk in your computer. Open it and install the Septentrio drivers.
After installation, when you connect the receiver to the PC, you will see 2 new COM ports, that you can use with your favourite terminal tool to read NMEA or have full access to the Mosaic using RxTools.

But the nicest thing of this receiver is that if you go to the web browser and write 192.168.3.1, the Septentrio web interface appears, that you can both to configure and monitor the receiver:

USB XBee
This USB-C connector gives you access to the UART of the XBEE radio (if you mount one), via an FTDI USB-to-UART converter. We find very practical to use this connector to power the board, so you can then connect and disconnect the GPS USB as your wish, without removing the power to the board. You can use any USB wall plug adapter you find at home.
To use this connector only as a power source, you don’t need any driver. You can use your PC, or connect to your USB wall adapter.
To use this connector to configure an XBee radio, you will need the VCP driver from FTDI: https://ftdichip.com/drivers/vcp-drivers/
Pixhawk connector
mosaic_H-Pixhawk
This connector is a standard JST GH that can be used to connect the simpleRTK3B Heading to a Pixhawk autopilot. You can also use this connector to power the board.
The Pixhawk JST-GH connector is following the Pixhawk standard:
  • 1: 5V_IN
  • 2: Mosaic COM3 RX (3.3V level)
  • 3: Mosaic COM3 TX (3.3V level)
  • 4: Timepulse output (3.3V level)
  • 5: Event input (3.3V level)
  • 6: GND
Please note that the board only includes GPS and doesn’t include magnetometer.
Arduino rails
mosaic_H-Arduino
simpleRTK3B Heading has optional rails to connect to other arduino UNO compatible devices.
  • GND: ground is available in the standard Arduino pins. You should always connect this line to your other board.
  • 5V IN/OUT:
    • When the LED next to this pin is OFF, you can power simpleRTK3B Heading from this pin. For example, just plug it on top of an Arduino UNO board, and simpleRTK3B Heading will turn ON. (Check if your Arduino can power 300mA @ 5V shields).
    • Alternatively, you can now use simpleRTK3B Heading to power other shields. Just turn ON the switch “5V=OUTPUT” and simpleRTK3B Heading board will output 5V at this pin.
  • IOREF: This pin affects the functionality of TX1, RX1, TX2, RX2 pins.
    • When plugging the simpleRTK3B Heading board on top of an Arduino UNO or Raspberry Pi, this pin is used to automatically define the voltage level of the communication pins (TX1, RX1, TX2, RX2).
    • When wiring your own cables to the board, this is an input that will define the voltage levels of the pins. If you input 1.8V, the next pins will be 1.8V level. It supports from 1.2V to 5.5V.
    • If you want to connect wires to the listed pins and 3.3V is OK for you, you just need to enable the switch “IOREF=3.3V.”
  • TX1, RX1, TX2, RX2: These pins work with the voltage level defined by IOREF.
    • TX1: Mosaic COM1 TX
    • RX1: Mosaic COM1 RX
    • TX2: XBee UART TX (this pin is also connected to Mosaic COM2 RX).
    • RX2: XBee UART RX (this pin is also connected to Mosaic COM2 TX).
High Power (HP) XBee socket
mosaic_Xbee-socket
The simpleRTK3B Heading has a High Power (HP) XBee socket. You can use this socket to connect an XBee compatible radio. The following pins are available:
  • VCC, which is a 3.3V output with a maximum current of 1A constant and peak 1.5A.
  • XBee UART RX, at 3.3V level
  • XBee UART TX, at 3.3V level
  • GND
The XBee socket is connected to Mosaic COM2.
Special function pins
mosaic_H-Special-function-pin
In addition to above, there’s also a few additional pins available for the most advanced users. If you are going to use simpleRTK3B Heading connected on top of an Arduino or Raspberry Pi and you don’t use any of these pins, it’s recommended to not connect the pins: you can cut the header in this pins to avoid the connection, and prevent unexpected behaviours.
  • Timepulse (TPS): 3.3V configuration time pulse output. The logic of this pin is inverted with the web interface. If the web interface you select HIGH, the pin will output LOW.
  • External Event (EVT): time synchronization input, maximum voltage 3.6V. This input is filtered to avoid glitches.
  • Logging Button (LOG): the logging feature can be controlled via web interface, but in case you want to add a button to control this feature.
    • Driving the LOGBUTTON pin low for 100 ms to 5 seconds toggles logging on and off.
    • Driving the LOGBUTTON pin low for more than 5 seconds and then releasing it unmounts the SD card if it was mounted, or mounts it if it was unmounted.
Remember that you can add a second XBee socket to your board with the Shield for Second XBee socket.

GPS/GNSS Antenna

simpleRTK3B Heading does not include, but requires a good quality GPS/GNSS antenna.
simpleRTK3B Heading supports L1/L2/Eb5 bands. If you want to get the most out of this module, we recommend a Budget Survey GNSS Multiband antenna.
The board is compatible with both active antennas supporting 3.3V supply and passive antennas. The maximum output current is 150mA @ 3.3V.
If you use it with the traditional cheap GPS antennas widely available, you will not achieve the expected performance.
IMPORTANT: The installation of the antenna is also a key point to achieve the best results.
  • It is mandatory to connect the antenna before powering the board.
  • The GPS/GNSS antenna should always be installed with the maximum possible view of the sky.
  • In the default configuration, the antennas should be placed longitudinally along the vehicle, with the master antenna (GPS1) positioned at the front.
  • In addition, if possible, it should be installed with a metallic plane behind, e.g. rooftop of the car, on a metal plate bigger than 20cm, etc.
  • The heading accuracy will depend on antenna distance, check image below. With a good installation with 0.5 meters, you can get decent results.
How GPS can help you measure the real heading of your vehicle heading curve
If you want to learn how installation impacts performance, please have a look at our GPS/GNSS antenna installation guide or look this video.

LEDs

mosaicH-LEDs
The board includes 7 status LEDs, which indicate that:
  • POWER: the simpleRTK3B Heading board has power.
  • PVT: LED lights when it was possible to calculate a position from the available satellite visibility.
  • NORTK: ON when no RTK, blinking when receiving correction data, OFF when the device is in RTK FIXED mode.
  • XBEE>GPS: The XBEE radio is receiving data over the air and sending it to the Mosaic.
  • GPS>XBEE: The Mosaic is outputting data to the XBee radio.
  • 5V IN/OUT: Indicates if there is voltage on that pin.
  • IOREF: Indicates if there is voltage on that pin. If the IOREF pin is enabled, the UARTs on Arduino rails are activated.

Buttons and swittches

mosaicH-Buttons-and-switch
There’s only one button: XBee Reset, and the good news is that you probably will not have to use it. This button is used to program the XBee radio if you want to update firmware, etc.
You will find also 1 switch under the XBee socket: it let you enable IOREF with 3.3V and 5V arduino pin as output so the board can power accessories like Shield for Second XBee socket.
At the same time this switch will also enable the arduino rail signals at 3.3V. Check the “Arduino Rails” section above to read more details about this.

Onboard datalogging (MicroSD card)

mosaic_H_datalog
simpleRTK3B Heading incorporates a microSD card reader for data logging. You can configure the datalogging details from Septentrio’s web interface.
A peculiarity of Septentrio datalogging is that storage inside microSD card is done in batches. For example, if you only enable GGA message for storage 1 time per second and you only leave the system up for 10 seconds, there will be no data inside the memory card, because you didn’t reach the minimum data size for storage. We recommend enabling a few messages per second to make sure when powering down a minimum number of last messages are lost.
In case you want to control logging with a button, there’s a pin labelled LOG that is connected to the LOGBUTTON function of the Mosaic module: if you connect this pin to GND you can trigger externally start / stop of recording. Otherwise you can simply do it from the web interface or leave it always O.

Get started

Connect to Septentrio web interface
  1. Connect the GNSS antenna to your receiver. Make sure the antenna has a good view of the sky for testing functionality. Or you won’t see satellites view and signal.
  2. Connect the receiver to your PC via the USB port labelled as POWER+GPS. When you connect this product to a PC for the first time, the PC may not recognize it. you will only see a new Hard Disk in your computer. Open it and install the Septentrio driver. After installation, disconnect and reconnect again, your PC will recognize the receiver. This only need to be done once. 
  3. Open a web browser and type in 192.168.3.1
how to configure simpleRTK3B as static base station Septentrio web interface
Send NMEA messages to Xbee Socket
  1. In the menu bar go to Communication–>Serial Port.
Userguide-simpleRTK3B4
  1. Set the Baud rate of COM2 at 115’200 bps. Because most of our communication plug-in works at 115’200 bps. Press Ok and Save configuration.
Userguide-simpleRTK3B5
  1. In the menu bar go to NMEA/SBF Out. Press +New NMEA stream–>Serial port–>COM2.
Userguide-simpleRTK3B6
  1. At Interval choose 1 sec and check your preferred NMEA messages. If you don’t know which one to choose, we suggest to check GGA, GSA, GSV, RMC and VTG. Because they are used by most of the applications. Select these messages and press Finish. But be careful, as Bluetooth bandwidth is limited. Enabling this message will result in a maximum transmission rate of 1Hz. If you want to use at higher frequency you can use the USB connector or reduce the number of messages being transmitted to avoid exceeding the Bluetooth transmission capacity.
Userguide-simpleRTK3B-7
  1. You will observe Data Streams outputting NMEA and RTCM messages to COM2. Press Ok and Save configuration.
Userguide-simpleRTK3B-8
Connect to NTRIP

In order to achieve centimeter/millimeter level accuracy with our GNSS receivers, you need to have corrections.
If you don’t have your own base station for corrections, you can find third party base stations at RTK Correction Services in your Country. Register and get you server, port, username, password and mount point of your NTRIP correction. We will use it later.

  1. Share your internet connection with the receiver via USB and receiving RTK corrections by following the video tutorial. 
  1. You will see corrections coming in and in a few minutes, you will have RTK Float or Fixed.
    Note that when you restart or reboot the receiver, the IP address will change. You will need to check the new IP address and connect your receiver.
Userguide-simpleRTK3B-10

Heading configuration

  1. The heading result is the angle from True North to the Baseline of the master antenna (labelled as GPS1 on board) to the slave antenna (labeled as GPS2) in a clockwise direction.Pitch angle refers to the angle of the car or drone relative to the horizontal plane.
  2. In the default configuration, the antennas should be placed longitudinally along the vehicle, with the master antenna (GPS1) positioned at the back.
simpleRTK3B_Compass-pitch-angel
  1. There is a minimum distance required between 2 antennas for an accurate heading to be generated. Heading accuracy can be improved by increasing the baseline length (distance between the 2 antennas). In general minimum 1 meter distance (baseline length) is required to achieve satisfactory sub-degree precision under non-ideal condition. In practical, this is not possible for many vehicles. With a good installation with 0.5 meters, you can get decent results. With 0.3 meters it’s possible to get heading, but it’s output sometimes will be a bit noisy. But it might be good enough for some applications.
How GPS can help you measure the real heading of your vehicle heading curve
  1. It is recommended that both GNSS antennas be identical and have the same physical orientation relative to each other (i.e. the antenna cable should exit in the same direction on both antennas). This will ensure best RF phase center alignment and heading accuracy. The actual RF phase center is often offset from the physical center of the antenna case.For optimal results, ensure that the RF cable lengths for both antennas are identical.
  1. Open Septentrio web interface. If you can not install the antennas with default setup, go to GNSS–> Attitude. At Attitude Offset to set the Heading and Pitch offset.
  2. At Attitude Information you can check the heading information of your vehicle.
Userguide simpleRTK3B heading Attitude

Septentrio documentation

For additional configuration information, such as upgrading firmware or configuring the receiver as a base or rover, refer to the Septentrio Configuration Page.
If you’re looking for more detailed guidance, explore the following resources and tutorials:

Accessories

You can add any of these features (and more) with our XBee plugins:

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