can

README

🔌 CAN Go

CAN toolkit for Go programmers.

can-go makes use of the Linux SocketCAN abstraction for CAN communication. (See the SocketCAN documentation for more details).

Examples

Use DBC file to parse OBC CanFd data

func main() {
	dbcFile = "/path/xxxx.dbc"
	obcCanFd, err := obc.NewObcCanFD(dbcFile)

	canID = uint32(298)
	canDataHexStr = "1A02A300C23290802"
	params := obcCanFd.ParseCanHexStr(canID, canDataHexStr)
	fmt.Printf("canID(%d), canData(%v)", canID, params)
}

Setting up a CAN interface

func main() {
	// Error handling omitted to keep example simple
	d, _ := candevice.New("can0")
	_ := d.SetBitrate(250000)
	_ := d.SetUp()
	defer d.SetDown()
}

Receiving CAN frames

Receiving CAN frames from a socketcan interface.

func main() {
	// Error handling omitted to keep example simple
	conn, _ := socketcan.DialContext(context.Background(), "can", "can0")

	recv := socketcan.NewReceiver(conn)
	for recv.Receive() {
		frame := recv.Frame()
		fmt.Println(frame.String())
	}
}

Sending CAN frames/messages

Sending CAN frames to a socketcan interface.

func main() {
	// Error handling omitted to keep example simple

	conn, _ := socketcan.DialContext(context.Background(), "can", "can0")

	frame := can.Frame{}
	tx := socketcan.NewTransmitter(conn)
	_ = tx.TransmitFrame(context.Background(), frame)
}

Generating Go code from a DBC file

It is possible to generate Go code from a .dbc file.

$ go run github.com/cleey/can-go/cmd/cantool generate <dbc file root folder> <output folder>

In order to generate Go code that makes sense, we currently perform some validations when parsing the DBC file so there may need to be some changes on the DBC file to make it work

After generating Go code we can marshal a message to a frame:

// import etruckcan "github.com/myproject/myrepo/gen"

auxMsg := etruckcan.NewAuxiliary().SetHeadLights(etruckcan.Auxiliary_HeadLights_LowBeam)
frame := auxMsg.Frame()

Or unmarshal a frame to a message:

// import etruckcan "github.com/myproject/myrepo/gen"

// Error handling omitted for simplicity
_ := recv.Receive()
frame := recv.Frame()

var auxMsg *etruckcan.Auxiliary
_ = auxMsg.UnmarshalFrame(frame)

Running integration tests

Building the tests:

$ make build-integration-tests

Built tests are placed in build/tests.

The candevice test requires access to physical HW, so run it using sudo. Example:

$ sudo ./build/tests/candevice.test
> PASS

Documentation

Overview

Package can provides primitives for working with CAN.

See: https://en.wikipedia.org/wiki/CAN_bus

Index

• Constants
• type Frame
  • func (f Frame) JSON() string
  • func (f Frame) MarshalJSON() ([]byte, error)
  • func (f Frame) String() string
  • func (f *Frame) UnmarshalJSON(jsonData []byte) error
  • func (f *Frame) UnmarshalString(s string) error
  • func (f *Frame) Validate() error
• type FrameMarshaler
• type FrameUnmarshaler
• type Message

Constants

const (
	MaxID         = 0x7ff
	MaxExtendedID = 0x1fffffff
)

CAN format constants.

Types

type Frame

type Frame struct {
	// ID is the CAN ID
	ID uint32
	// Length is the number of bytes of data in the frame.
	Length uint8
	// Data is the frame data.
	Data Data
	// IsRemote is true for remote frames.
	IsRemote bool
	// IsExtended is true for extended frames, i.e. frames with 29-bit IDs.
	IsExtended bool
}

Frame represents a CAN frame.

A Frame is intentionally designed to fit into 16 bytes on common architectures and is therefore amenable to pass-by-value and judicious copying.

func (Frame) JSON

func (f Frame) JSON() string

JSON returns the JSON-encoding of f, using hex-encoding for the data.

Examples:

{"id":32,"data":"0102030405060708"}
{"id":32,"extended":true,"remote":true,"length":4}

func (Frame) MarshalJSON

func (f Frame) MarshalJSON() ([]byte, error)

MarshalJSON returns the JSON-encoding of f, using hex-encoding for the data.

See JSON for an example of the JSON schema.

func (Frame) String

func (f Frame) String() string

String returns an ASCII representation the CAN frame.

Format:

([0-9A-F]{3}|[0-9A-F]{3})#(R[0-8]?|[0-9A-F]{0,16})

The format is compatible with the candump(1) log file format.

func (*Frame) UnmarshalJSON

func (f *Frame) UnmarshalJSON(jsonData []byte) error

UnmarshalJSON sets *f using the provided JSON-encoded values.

See MarshalJSON for an example of the expected JSON schema.

The result should be checked with Validate to guard against invalid JSON data.

func (*Frame) UnmarshalString

func (f *Frame) UnmarshalString(s string) error

UnmarshalString sets *f using the provided ASCII representation of a Frame.

func (*Frame) Validate

func (f *Frame) Validate() error

Validate returns an error if the Frame is not a valid CAN frame.

type FrameMarshaler

type FrameMarshaler interface {
	MarshalFrame() (Frame, error)
}

FrameMarshaler can marshal itself to a CAN frame.

type FrameUnmarshaler

type FrameUnmarshaler interface {
	UnmarshalFrame(Frame) error
}

FrameUnmarshaler can unmarshal itself from a CAN frame.

type Message

type Message interface {
	FrameMarshaler
	FrameUnmarshaler
}

Message is anything that can marshal and unmarshal itself to/from a CAN frame.