node-red-contrib-socketcan 1.2.5

node-red nodes for socketcan

npm install node-red-contrib-socketcan

This is a couple of nodes to read CAN frames from and send CAN frames to a CAN bus using socketcan. Socketcan is the standard CAN subsystem on Linux. Socketcan is not available on Windows.

This project is inspired by node-red-contrib-canbus (Rajesh Sola rajeshsola@gmail.com) which almost did what I needed but not quite.

can-utils is a good set of companion tools when working with socketcan.

Some info about bringing a (virtual) CAN interface up is here. If you need real CAN hardware TouCAN is a good choice (no affiliation except for using it myself).

This project is part of the VSCP (https://www.vscp.org) project.

Install

Go to node-red folder and

npm install node-red-contrib-socketcan

or install in node-red palette.

Sending CAN frames

socketcan-in node is provided for sending CAN frames. You can send standard or extended id frames, FD frames are supported.

Set up the interface to some real CAN hardware or use a virtual interface.

payload

Object/JSON formated message

The CAN message is defined as a JSON object with the following payload format

{
    "canfd":false,
    "ext":false,
    "rtr":false,
    "canid":123,
    "dlc":5,
    "data":[1,2,3,4,5]}
}

• ext - Marks the message as an extended id message.
• rtr - The message is a remote transmission request. No data should be specified in this case (set to null).
• canid - The canid for the CAN message. Must be less then 0x7ff for a standard CAN message.
• dlc - Number of databytes, 0-64.
• data - An array, comma separated list or buffer with data bytes. Set to null if no data.

String formated messages

The CAN message is defined as a string with the following payload format

<canid>#{R|data}

• canid - Less than 0x7ff and with less than three digits for a standard id. Always defined in hex format.
• data - The data part for the can frame. Always in hex format.
• R - Specifies a remote transmission request frame.

Examples

123#DEADBEEF - standard frame 
5AA#         - Standard frame no data
1F334455#1122334455667788 - extended frame
123#R         - for remote transmission request.
123##         - FD frame no data
123##AA       - FD frame standard

Receiving CAN frames

socketcan-out node is provided for receiving CAN frames. You can receive standard or extended CAN id frames.

Set up the interface to some real CAN hardware or use a virtual interface.

Payload

The payload is always a Javascript object on the following form.

{ timestamp: 1552881174, ext: 0, rtr: 0, canid: 123, dlc: 5, data: [1,2,3,4,5] }

• canid - The standard or extended can id.
• ext - Set to true if this is a extended id frame. False otherwise.
• rtr - Specifies a remote transmission request frame if set to true.
• dlc - Number of databytes.
• data - An array with data or null or an empty array if no data.

The timestamp (in microseconds) is generated by the node if not supplied by the interface.

Example flow

Enable a virtual CAN interface with

$ modprobe vcan
$ sudo ip link add dev vcan0 type vcan
$ sudo ip link set up vcan0

install can-utils with

sudo apt install can-utils

Receive CAN frames with

candump vcan0

Send CAN frames with

cansend vcan0 123#1122334455

Use this flow to interact with the other tools.

[
    {
        "id": "829af3ee.a57c1",
        "type": "tab",
        "label": "Flow 1",
        "disabled": false,
        "info": ""
    },
    {
        "id": "b2855d5b.1215c8",
        "type": "socketcan-config",
        "z": "",
        "interface": "can0"
    },
    {
        "id": "38e8307.1653f5",
        "type": "socketcan-config",
        "z": "",
        "interface": "vcan0"
    },
    {
        "id": "7b24a62e.8f5458",
        "type": "debug",
        "z": "829af3ee.a57c1",
        "name": "",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "false",
        "x": 350,
        "y": 360,
        "wires": []
    },
    {
        "id": "5f671b29.cd24bc",
        "type": "socketcan-out",
        "z": "829af3ee.a57c1",
        "name": "socketcan-out",
        "config": "38e8307.1653f5",
        "x": 150,
        "y": 360,
        "wires": [
            [
                "7b24a62e.8f5458"
            ]
        ]
    },
    {
        "id": "caba412f.047b2",
        "type": "socketcan-in",
        "z": "829af3ee.a57c1",
        "name": "socketcan-out",
        "config": "38e8307.1653f5",
        "x": 360,
        "y": 120,
        "wires": []
    },
    {
        "id": "a64240cb.3f0788",
        "type": "inject",
        "z": "829af3ee.a57c1",
        "name": "Send object - std",
        "topic": "",
        "payload": "{\"ext\":false,\"canid\":123,\"dlc\":5,\"data\":[1,2,3,4,5]}",
        "payloadType": "json",
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "x": 160,
        "y": 120,
        "wires": [
            [
                "caba412f.047b2"
            ]
        ]
    },
    {
        "id": "3ff96369.ef6f5c",
        "type": "inject",
        "z": "829af3ee.a57c1",
        "name": "Send string - std",
        "topic": "",
        "payload": "123#00112233",
        "payloadType": "str",
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "x": 160,
        "y": 200,
        "wires": [
            [
                "caba412f.047b2"
            ]
        ]
    },
    {
        "id": "6879c00a.5edb68",
        "type": "inject",
        "z": "829af3ee.a57c1",
        "name": "Send string - ext",
        "topic": "",
        "payload": "1F334455#1122334455667788",
        "payloadType": "str",
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "x": 160,
        "y": 240,
        "wires": [
            [
                "caba412f.047b2"
            ]
        ]
    },
    {
        "id": "1ee3b274.4cb8fe",
        "type": "inject",
        "z": "829af3ee.a57c1",
        "name": "Send object - ext",
        "topic": "",
        "payload": "{\"ext\":true,\"canid\":32278,\"dlc\":5,\"data\":[1,2,3,4,5]}",
        "payloadType": "json",
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "x": 160,
        "y": 160,
        "wires": [
            [
                "caba412f.047b2"
            ]
        ]
    },
    {
        "id": "391a4c45.7acd8c",
        "type": "comment",
        "z": "829af3ee.a57c1",
        "name": "Send CAN frames in using different payloads on VCAN0",
        "info": "",
        "x": 260,
        "y": 80,
        "wires": []
    },
    {
        "id": "912f9928.da2758",
        "type": "comment",
        "z": "829af3ee.a57c1",
        "name": "Receiove CAN data from interface VCAN0",
        "info": "",
        "x": 220,
        "y": 320,
        "wires": []
    }
]

Debugging

It is possible to get extra debug information from the nodes in this package.

Issue

export NODE_DEBUG=socketcan-in

before starting node-red to get extra debug info for the socketcan-in node.

Issue

export NODE_DEBUG=socketcan-out

before starting node-red to get extra debug info for the socketcan-out node.

Issue

export NODE_DEBUG=socketcan-in socketcan-out

before starting node-red to get extra debug info for both the socketcan-in and socketcan-out node.