node-red-contrib-socketcan 1.0.7

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 but currently not FD frames.

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

{
    "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, 0-8.
• 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.

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 canuils

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.