node-red-contrib-socketcan 1.0.5
node-red nodes for 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.