User Guide: simpleRTK3B Fusion

Product Overview

You can use simpleRTK3B Fusion as a standalone board or as an Arduino shield.
The main component of simpleRTK3B Fusion is triple-band Unicore UM981 module.
If you are an advanced Unicore GPS user, you might want to have a look at the extensive Unicore documentation.

Hardware

Pinout definition

Power

The simpleRTK3B Fusion 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.

Communication ports

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

USB GPS

This USB-C connector gives you access via FTDI USB-to-UART converter, to COM1 of the UM980 module.
You can connect this interface to your preferred mobile phone, tablet, or PC and start receiving NMEA data.
After connecting the receiver to the PC, you will see 1 new COM ports, that you can use with your favorite terminal tool to read NMEA or have full access to the UM980 using the UPrecise tool.

By default NMEA is disabled on this module so we recommend you to start with the UPrecise tool.
If your PC doesn’t recognize the device, you will need the VCP driver from FTDI: https://ftdichip.com/drivers/vcp-drivers/

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

This connector is a standard JST GH that can be used to connect the simpleRTK3B Fusion 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: Unicore COM3 RX (3.3V level)
3: Unicore COM3 TX (3.3V level)
4: Timepulse output (3.3V level)
5: Extint (3.3V level)
6: GND

Please note that the board only includes GPS and doesn’t include magnetometer.

Arduino rails

simpleRTK3B Budget 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, can power simpleRTK3B Budget from this pin.
  For example, just plug it on top of an Arduino UNO board, and simpleRTK3B Budget will turn ON. (check if your arduino can power 300mA @ 5V shields).
- Alternatively, you can now use simpleRTK3B Budget to power other shields.
  Just turn ON the switch “5V=OUTPUT” and simpleRTK3B Budget board will output 5V at this pin.
IOREF: This pin is disconnected when the onboard switch is towards “IOREF = NC”.
Alternatively it outputs 3.3V when the onboard switch is towards “IOREF = 3V3”. You can use this functionality to provide a voltage reference to other Shields that require this pin as an input.
TX2,RX2,TX3,RX3:These pins work as an output at 3.3V, and as an input accepting from 2.7 to 3.6V.
- TX2: Unicore COM2 TX (this pin is also connected to XBee UART RX)
- RX2: Unicore COM2 RX (this pin is also connected to XBee UART TX)
- TX3: Unicore COM3 TX
- RX3: Unicore COM3 RX

High Power (HP) XBee socket

The simpleRTK3B Fusion 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 maximum current 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 Unicore COM2.
Remember that you can add a second XBee socket to your board with the Shield for Second XBee socket.

Special function pins

In addition to above, there’s also a few additional pins available for the most advanced users. These pins are also available in the JST connector, as in the simpleRTK3B Pro.

If you are going to use simpleRTK3B Fusion 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 behaviors.

Timepulse (TPS): 3.3V configuration time pulse output.
Extint (EXTINT): time synchronization input, maximum voltage 3.6V.
This input is filtered to avoid glitches.

Remember that you can add a second XBee socket to your board with the Shield for Second XBee socket.

GPS/GNSS Antenna

simpleRTK3B Fusion does not include, but requires a good quality GPS/GNSS antenna.

simpleRTK3B Fusion supports full L1/L2/L5 bands. If you want to get the most out of this module, we recommend a Triple Band simpleANT3B series 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: It is mandatory to connect the antenna before powering the board.

The installation of the antenna is also a key point to achieve the best results. The GPS/GNSS antenna should always be installed with the maximum possible view of the sky.

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.

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

The board includes 7 status LEDs, which indicate that:

POWER: the simpleRTK3B Fusion 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 devices is in RTK FIXED mode.
XBEE>GPS: The XBEE radio is receiving data over the air and sending it to the Unicore.
GPS>XBEE: The Unicore is outputting data that the XBEE radio is receiving and sending over the air.
5V IN/OUT: Will indicate you if there is voltage on that pin.
IOREF: Will indicate you if the IOREF pin is enabled, which activates the UARTs on arduino rails.

Buttons and switches

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.

Get started

Connect to UPrecise

Connect the GNSS antenna to your receiver. Make sure the antenna has a good view of the sky for testing functionality.
Connect the receiver to your PC via the USB port labelled as POWER+GPS.
Open Uprecise. Select the COM port (If you don’t know which COM port check the device manager of your PC). Press Connect.

Click the Receiver Configuration icon on the right side menu bar. Here you can enable you preferred NMEA messages. We recommend check GGA, GSA, GSV, GST and RMC. It will work well with SW Maps and most applications. Then click Enter.

At Menu bar choose the Data Stream icon. At Data Stream window type in SAVECONFIG and press Enter or Send to all .
On the Data Stream you will see Command, SAVECONFIG, response: OK. It means your configuration is saved to the Flash of your receiver.

You will see the Constellation, Data Steam and Tracking Status on the screen.

Send NMEA messages to Xbee Socket

The Xbee socket is connected to Unicore COM2. If you want to connect with Bluetooth, BLE, radio or other communication plugins, you need to enable NMEA messages on COM2.
For example if you want to send GGA to COM2, at the commend window type in GPGGA COM2 1. It will output 1Hz GGA message at COM2. Repeat the same for the NMEA messages you need.

Connect to NTRIP

Click the toolbox icon and select RTCM.

Click Input. Choose Ntrip Client. Set your Ntrip Caster Host, Port, Mount point, ID and Password. If your Ntrip Caster need the location of your rover, set GGA Location reporting at 1, and select CurrentSerialGGA. Click Ok.