Fastnet is the propriatory protocol used by B&G on some older instruments, tested on Hydra/H2000. It might work on other systems. I developed this for personal use and publishing for general interest only.
This code listens for fastnet data on the bus, interprets the message and then broadcasts a UDP packet with the applicable NMEA sentence.
This is the companion app to the library pyfastnet
Fastnet uses two-wire differential transmission and I have had success using RS-485/CAN bus connections. The CAN Hat has the option to enable 120ohm teminations which I am using.
These are known to work
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DTECH USB RS422/RS485 USB dongle Works out of the box
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Waveshare RS485 CAN HAT add this to /boot/firmware/config.txt
dtoverlay=mcp2515-can0,oscillator=12000000,interrupt=25,spimaxfrequency=2000000
Connections
- Fastnet White: RS485 Data +
- Fastnet Green: RS485 Data -
- Baud Rate: 28,800
- Data Bits: 8
- Parity: Odd
- Stop Bits: 2
I have been running on Rasperry Pi, a stock install is sufficient.
pip3 install pyfastnet
Virtual mode - txt file input
~/python_environment/bin/python3 fastnet2ip.py --file example2_fastnet_data.txt --udp-port 2002 --log-level ERROR --live-data
Real mode - serial port input
~/python_environment/bin/python3 fastnet2ip.py --serial /dev/ttyUSB0 --udp-port 2002 --log-level ERROR
Support NMEA messages broadcast via UDP
- VHW (Boatspeed)
- DBT (Depth)
- RSA (Rudder Angle)
- MWD (True Wind Direction)
- MWV (True Wind Angle / Speed)
- MWV (Apparent Wind Angle / Speed)
- MDA (Air Temp, Sea Temp, Barometric pressure)
- HDM (Heading)
- VTG (COG and SOG)
- VDR (Tide Set/Drift)
- GLL (Lat/Lon)
- Multiple XDR sentences including
- Battery Voltage
- Heel
- Fore/Aft trim
- raw_wind_speed (B&G transducer raw data)
- raw_wind_angle (B&G transducer raw data)
- raw_boat_speed (B&G transducer raw data)
Console output - testing only
Includes a 'fastnet2ip.service' file recommended for systemd architecture
cp fastnet2ip.service /etc/systemd/system/
systemctl daemon-reload
systemctl enable fastnet2ip
systemctl start fastnet2ip
This is the approximate approach
- collect data from serial port or file buffer
- Add it to the queue for processing
- Retrive valid message from the queue (remaining partial data is left)
- Iterate through messages
- Updating live_view
- Trigger NMEA message sending
- Wait until more data is available on the input buffer
Record and playback of live data. I use this to capture live data from the boat so I can play it back offline for testing
- use record_fn.py to capture raw Fastnet data into a .txt file, no processing is done, it captures the raw data. To use this you will need to edit the serial port address in the .py file.
- Recorded data can be played back using fastnet2ip.py using the --file option
Given the differential nature of the connection, loopback if not feasable. Seperate transmit and receive ports required for physical bench testing.
- trlafleur - Collector of significant background
- Oppedijk - Background
- timmathews - Significant implementation in Cpp
- Significant help from chatGPT!