Moitessier HAT


  • High-sensitivity (better than -112 dBm) dual channel AIS receiver with SMA antenna connector.

  • High-performance GNSS receiver with integrated patch antenna and external antenna support via BNC connector.

  • Compass, heel and trim from gyroscope, accelerometer and magnetometer sensors (IMU).

  • Barometric pressure.

  • Standalone usage or in combination with Raspberry Pi. Standalone usage requires 3.3V power supply and sensors are controlled by the HAT’s microcontroller

  • Fully compatible with Raspberry Pi models 2, 3 and 3+ supporting 40-pin IO header.

  • Data communication via SPI (AIS, GNSS and meta data) and via I2C (sensor data). Data accessible via device driver and device file.

  • Supports ID EEPROM and automatic device tree loading.

  • 3 status LEDs (AIS status, GNSS status, error).

  • Full OpenPlotter compatible.

This item is available in our Web Shop.

Mounting the HAT

Removing the HAT

You can damage your Raspberry or your HAT if you do not remove it carefully, please watch this video before removing:

Mounting the HAT into the case

This item is available in our Web Shop.

External antennas


You need to connect a suitable VHF antenna to the HAT in order to be able to get AIS targets. The HAT uses an SMA female connector for AIS reception. If your antenna uses a different connector you will need an adapter.


There is an integrated patch antenna for GNSS and it should be enough for most cases but if you have a metallic boat or you place the HAT under metallic equipment, you may need an optional external GNSS antenna. The HAT uses a BNC female connector for GNSS reception. If your antenna uses a different connector you will need an adapter.

This item is available in our Web Shop.

Installing drivers

Before installing Moitessier HAT drivers update to the latest OpenPlotter version.

After mounting the HAT go to OpenPlotter - Tools - Moitessier HAT. A small window will open, press start.

A new window will open and you will see:

Moitessier HAT is attached. Moitessier HAT package is not installed!

Go to Install tab and check your Kernel version. Only the first 3 figures are important, in this case 4.14.34

Select the package matching your Kernel version in Available packages field and press Install.

A terminal window will open. The drivers will be installed and the firmware of the HAT will be updated. The system will automatically reboot at the end of the process.

If your HAT stops working after a major OpenPloter update, this means that your Kernel has been updated too. In this case go back to this window and repeat the procedure. If a matching package does not exist, download the right package from:

Configuring GNSS and AIS reception

After installing drivers a new device should appear in Serial tab. Select the new device an press auto.

The system will find the best settings for you.

  • You can change the field name /dev/ttyOP_ value as you want (only numbers, lowercase letters and no symbols or spaces).

  • You could set the assignment field value to Kplex too but we recommend GPSD.

  • Select Remember port (position on the USB-hub) only if the HAT creates some conflict with another device.

Press apply and you are done! go to OpenCPN and you should get position and AIS targets.

Configuring compass, heel and trim reception

To enable magnetic heading, heel and trim reception you have to go to pypilot tab.

Select IMU only in pypilot mode or basic autopilot if you have a pypilot installation.

Check the type of data you want to enable, heading or/and trim and heel (pitch, roll).

Select a translation rate (0.5 or 1 second should be enough).

Press Apply changes and you are done!

Go to OpenCPN and check that you are getting magnetic heading, heel and pitch data.

OpenPlotter constantly and automatically calibrates the IMU in order to get accurate magnetic heading readings. Read the calibration chapter to follow some advices:

Configuring pressure reception

Moitessier HAT has a MS5607-02BA03 sensor for barometric pressure and temperature. Atmospheric pressure readings are reliable, but temperature readings can not be considered reliable because it is affected by the temperature of the HAT and the Raspberry. However, it is a good way to get the temperature of your system.

To learn how to configure this feature, go to I2C chapter and follow the example:

Pressure and temperature data are generated in Signal K format. If you want to get pressure and temperature in OpenCPN you have to convert data into NMEA 0183 format.

Open the Signal K administrator and login. Go to Server - Plugin Config - Convert Signal K to NMEA0183 and check Active.

Scroll down and check:

  • XDR (Barometer) - Atmospheric Pressure

  • XDR (TempAir) - Air temperature

Press Submit and you are done.

LED status information


  • LED switched on: No AIS data reception

  • LED flashing at variable/inconsistent frequency: AIS data is received


  • LED switched on: No GNSS fix

  • LED flashing once per second: GNSS fix


  • LED switched off: No error occurred

  • LED flashing at variable/inconsistent frequency: Internal buffer overflows (the data is processed too slowly by the Raspberry Pi)

  • LED flashing at consistent frequency: system error (read the device information to get system error code)

Getting info from the HAT

Work in progress.

Advanced settings

Work in progress.


You can write to Rooco or ask for help in OpenMarine forums: