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go-nmea-client

WORK IN PROGRESS Only public because including private Go library is too much of a hustle for CI

Go library to read NMEA 2000 messages from SocketCAN interfaces or USB devices (Actisense NGT1/W2K-1 etc).

In addition, this repository contains command line application n2k-reader to provide following features:

  • Can read input from:
    • files
    • TCP connections
    • serial devices
  • Can read different input formats:
    • SocketCAN format
    • CanBoat raw format
    • Actisense format:
      • NGT1 Binary,
      • N2K Ascii,
      • N2K Binary,
      • Raw ASCII
      • EBL (log files from W2K-1 device, NB: NGT1 format is different)
  • Can output read raw frames/messages as:
    • JSON,
    • HEX,
    • BASE64,
    • CanBoat format
  • Can assemble Fast-Packet frames into complete Messages
  • Can decode CAN messages to fields with CanBoat PGN database
  • Can output decoded messages fields as:
    • JSON (stdout)
    • CSV file (each PGN has own csv file). columns (fields) can be customized
  • Can send STDIN input to CAN interface/device
  • Can do basic NMEA2000 bus NODE mapping (which devices/nodes exist in bus)
    • Can list known nodes (send !nodes as input)
    • Can request nodes NAMES from STDIN (send !addr-claim as input)

Disclaimer

This repository exists only because of CanBoat authors. They have done a lot of work to acquire knowledge of NMEA2000 protocol and made it free.

NMEA2000 reader

Compile NMEA2000 reader for different achitectures/platforms (AMD64,ARM32v6,ARM32v7,ARM64,MIPS32 (softfloat)).

make n2kreader-all

Create Actisense reader that can be run on MIPS architecture (Teltonika RUT955 router ,CPU: Atheros Wasp, MIPS 74Kc, 550 MHz)

GOOS=linux GOARCH=mips GOMIPS=softfloat go build -ldflags="-s -w" -o n2k-reader-mips cmd/n2kreader/main.go

Help about arguments:

./n2k-reader -help

Example usage:

Run reader suitable for Raspberry Pi Zero with Canboat PGN database (canboat.json). Only decode PGNs 126996,126998 and output decoded messages as JSON.

./n2kreader-reader-arm32v6 -pgns ./canboat.json -filter 126996,126998 -output-format json
  • You can write data to NMEA bus by sending text to STDIN. Example 6,59904,0,255,3,14,f0,01 + \n sends PGN 59904 from src 0 to dst 255 requesting PGN 126996 (0x01, 0xf0, 0x14)
  • !nodes - lists all knowns node NAME and their associated Source values
  • !addr-claim - sends broadcast request for ISO Address Claim

Read device /dev/ttyUSB0 as ngt format, filter out PGNS 59904,60928 and output decoded messages as json:

./n2k-reader-arm32v6 -pgns canboat.json -input-format ngt -device "/dev/ttyUSB0" -filter 59904,60928 -output-format json

Read file as n2k-ascii format and output decoded messages as json format:

./n2k-reader -pgns=canboat/testdata/canboat.json \
   -device="actisense/testdata/actisense_n2kascii_20221028_10s.txt" \
   -is-file=true \
   -output-format=json \
   -input-format=n2k-ascii

Read file as canboat-raw format, filter out PGNS 127245,127250,129026 and append decoded messages as new lines to CSV files with given fields as columns:

./n2k-reader-amd64 -pgns canboat/testdata/canboat.json \
  -device canboat/testdata/canboat_format.txt \
  -np \
  -is-file \
  -input-format canboat-raw \
  -csv-fields "127245:_time_ms,position,directionOrder;127250:_time_ms(100ms),heading;129026:_time_ms,cog,sog"

This is instructs reader to treat device actisense/testdata/actisense_n2kascii_20221028_10s.txt as an ordinary file instead of serial device. All input read from device is decoded as Actisense N2K binary protocol ( Actisense W2K-1 device can output this) and print output in JSON format.

Read Actisense EBL log file as BST-95 format (created by W2K-1 device) and output decoded messages as json format:

./n2k-reader -pgns=canboat/testdata/canboat.json \
   -device="actisense/testdata/actisense_w2k1_bst95.ebl" \
   -is-file=true \
   -output-format=json \
   -input-format=ebl

Library example

func main() {
	f, err := os.Open("canboat.json")
	schema := canboat.CanboatSchema{}
	if err := json.NewDecoder(f).Decode(&schema); err != nil {
		log.Fatal(err)
	}
	decoder := canboat.NewDecoder(schema)

	// reader, err = os.OpenFile("/path/to/some/logged_traffic.bin", os.O_RDONLY, 0)
	reader, err := serial.OpenPort(&serial.Config{
		Name: "/dev/ttyUSB0",
		Baud: 115200,
		// ReadTimeout is duration that Read call is allowed to block. Device has different timeout for situation when
		// there is no activity on bus. Can not be smaller than 100ms
		ReadTimeout: 100 * time.Millisecond,
		Size:        8,
	})
	if err != nil {
		log.Fatal(err)
	}
	defer reader.Close()

	config := actisense.Config{
		ReceiveDataTimeout:      5 * time.Second,
		DebugLogRawMessageBytes: false,
	}
	// device = actisense.NewN2kASCIIDevice(reader, config) // W2K-1 has support for Actisense N2K Ascii format
	device := actisense.NewBinaryDeviceWithConfig(reader, config)
	if err := device.Initialize(); err != nil {
		log.Fatal(err)
	}

	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer cancel()
	for {
		rawMessage, err := device.ReadRawMessage(ctx)
		if err != nil {
			if err == io.EOF || err == context.Canceled {
				return
			}
			log.Fatal(err)
		}
		b, _ := json.Marshal(rawMessage)
		fmt.Printf("#Raw %s\n", b)

		pgn, err := decoder.Decode(rawMessage)
		if err != nil {
			fmt.Println(err)
			continue
		}

		b, _ = json.Marshal(pgn)
		fmt.Printf("%s\n", b)
	}
}

Research/check following:

  1. https://gist.github.com/jackm/f33d6e3a023bfcc680ec3bfa7076e696