node-red-contrib-canal 1.0.15
CANAL (CAN abstraction error) interface node for node-red
node-red-contrib-canal
This is a node that interface a CANAL driver.
Tested with node v11.8.0 and below
This node is a CANAL interface for node-red. CANAL stands for CAN Abstraction Layer and is the least common denominator for low level drivers for the Very Simple Control Protocol, VSCP. In the VSCP world CANAL driver is also called level I drivers.
The CANAL interface is documented here
There are plenty of CANAL drivers available. Some of them are documented here
You always send and receive CAN messages through a CANAL interface. This is just the abstraction and for example VSCP pack VSCP events into CAN packages for some types of events. You can actually pack anything you like and anything the driver expect. The format is CAN but the meaning for each packet is up to you or at least the CANAL driver maker.
Install
Install with
npm install node-contrib-vscp-canal
or install from the node-red user interface.
Usage
The CANAL node have one input that is used to send CAN messages to the CANAL driver and one output that receive CAN messages from the driver.
You have the option to automatically translate VSCP events to/from the node by selecting Use VSCP translation in the configuration. This is convenient if you work with VSCP hardware, but you have always the option to use node-red-contrib-vscp as an alternative as it contains nods that does the translation to.
The configuration let you define CANAL drivers on a system level and then select which driver to use for the moment. This is often convenient and time saving when you work with different CANAL drivers.
You configure a CANAL driver by giving it a descriptive name. The you set the path to the actual driver. The configuration string is specific for each driver so you have to read the documentation for the driver you want to use to understand required parameters. This is also true for the flags value, but with the difference that tha flags value is numeric instead of a semicolon separated string.
When you have setup one or more drivers select it for the CANAL node and deploy. The status of the node will tell you if the interface is opened OK or not. If all is OK you can start to use the node.
Select the Use VSCP translation if you want to work with VSCP events instead of CAN messages.
Sending CAN messages
You can send CAN messages either as JSON objects or strings.
JSON objects
To send a CAN message on JSON object form you send something like this
{
"ext":false,
"rtr":false,
"canid":123,
"dlc":5,
"data":[1,2,3,4,5]}
}
You can omit dlc which is data count, ext which marks an extended CAN message (default is false) and rtr which is remote transfer request (default is false).
Leave data as an empty array if the CAN message has no data.
String
IUf you prefer you can send CAN messages on string form. The format is
<canid>#{R|data}
All data should be hexadecimal.
canid - A standard id is three hexadecimal characters, an extended id is eight hexadecimal characters. The canid for the CAN message must be less than 0x7ff for a standard CAN message.
data is a hex number for each data byte. Empty if no data.
R is a remote transmission request and in this case there should be no data.
Examples of format
123#DEADBEEF - standard frame
5AA# - Standard frame no data
1F334455#1122334455667788 - extended frame
123#R - for remote transmission request.
Sending VSCP events
Select the Use VSCP translation if you want to work with VSCP events instead of CAN messages. Now you can send VSCP events directly. You can send VSCP events as JSON objects or as strings.
JSON object
A typical VSCP event looks like.
{ "vscpHead":0,
"vscpObId":0,
"vscpClass":10,
"vscpType":6,
"vscpGuid":"ff:ee:dd:cc:bb:aa:99:88:77:66:55:44:33:22:11:00",
"vscpTimeStamp":1234567,
"vscpDateTime":"2018-03-03T12:01:40Z",
"vscpData":[1,2,3,4],
}
Parameter you omit will often get meaningful defaults.
String
The string form for the VSCP event looks like this
head,class,type,obid,datetime,timestamp,GUID,data0,data1,data2,...........
and in real numbers
0,20,3,,,0,-,15,14,13,12,11,10,9,8,7,6,5,4,3,2,0,0,1,35
Receiving CAN messages
When the node is connected to the driver CAN messages will be received on JSON object form.
A typical received CAN message looks like this
{
id: 546
flags: 0
obid: 0
timestamp: 0
data: array[3,17,34,51]
}
flags will have bit one set for an extended id message and bit two set for a remote transmission message.
Receiving VSCP events
Select the Use VSCP translation if you want to work with VSCP events instead of CAN messages. Now you will receive VSCP events directly. Received VSCP events are always on JSON object form.
A typical VSCP event looks like.
{ "vscpHead":0,
"vscpObId":0,
"vscpClass":10,
"vscpType":6,
"vscpGuid":"ff:ee:dd:cc:bb:aa:99:88:77:66:55:44:33:22:11:00",
"vscpTimeStamp":1234567,
"vscpDateTime":"2018-03-03T12:01:40Z",
"vscpData":[1,2,3,4],
}
Constants
If you want to use CANAL constants you can add node-canal to node-red.
First go to your .node-red folder and install node-canal with
npm install node-canal
then add node-canal to the node-red settings.js file(also in the .node-red folder).
functionGlobalContext: {
CANAL:require('node-canal')
}
Now restart node-red with
systemctl restart nodered
You can now use all constants defined in node-canal. See the node-canal documentation for more info.
For work with VSCP the constants for events (VSCL classes and types) may be useful. See the documentation for node-red-contrib-vscp for a guide on how to do this.
Samples
Here is a simple sample flow that use the vscpl1drv_socketcan
[{"id":"ee3919bd.6af248","type":"canal","z":"295a49d7.d930e6","name":"CANAL","driver":"d5d84513.4b7e8","bvscp":false,"x":380,"y":120,"wires":[["fdbf3cc8.2b73"]]},{"id":"974a318d.1e024","type":"inject","z":"295a49d7.d930e6","name":"CAN object","topic":"","payload":"{\"id\":123,\"flags\":1,\"obid\":33,\"timestamp\":0,\"data\":[11,22,33,44,55,66,77,88]}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":130,"y":120,"wires":[["ee3919bd.6af248"]]},{"id":"fdbf3cc8.2b73","type":"debug","z":"295a49d7.d930e6","name":"Debug","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":410,"y":200,"wires":[]},{"id":"5127a4e3.0d6bcc","type":"inject","z":"295a49d7.d930e6","name":"std CAN String","topic":"","payload":"123#11223344","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":120,"y":160,"wires":[["ee3919bd.6af248"]]},{"id":"644daf4a.0ff268","type":"inject","z":"295a49d7.d930e6","name":"ext CAN String","topic":"","payload":"120A0600#11","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":120,"y":200,"wires":[["ee3919bd.6af248"]]},{"id":"43fa6ff1.5a451","type":"inject","z":"295a49d7.d930e6","name":"VSCP object","topic":"","payload":"{\"vscpHead\":80,\"vscpClass\":10,\"vscpType\":6,\"vscpGuid\":\"00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:2a\",\"vscpObid\":0,\"vscpData\":[11,22,33,44,55],\"vscpTimeStamp\":34565634,\"vscpDateTime\":\"2020-02-24T11:10:59.807Z\"}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":110,"y":360,"wires":[["4b35168.93e0d68"]]},{"id":"da3c6507.9aefa","type":"inject","z":"295a49d7.d930e6","name":"VSCP string","topic":"","payload":"0,20,3,,,,0:1:2:3:4:5:6:7:8:9:10:11:12:13:14:15,0,1,35","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":110,"y":400,"wires":[["4b35168.93e0d68"]]},{"id":"4b35168.93e0d68","type":"canal","z":"295a49d7.d930e6","name":"CANAL (VSCP)","driver":"d5d84513.4b7e8","bvscp":true,"x":400,"y":360,"wires":[["8a1901de.826508"]]},{"id":"8a1901de.826508","type":"debug","z":"295a49d7.d930e6","name":"Debug","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":410,"y":460,"wires":[]},{"id":"d5d84513.4b7e8","type":"canaldrv-config","z":"","name":"socketcan - vcan0","path":"/home/akhe/development/VSCP/vscpl1drv-socketcan/linux/vscpl1drv-socketcan.so.1.1.0","config":"vcan0","flags":"0"}]
In the exampel flow we use the Socketcan CANAL driver to illustrated examples. This driver is chosen because it is easy to use on a system without any extra hardware which means everyone can take it for a test. candump/cansend from the can-utils package is useful tools. Install can-utils with
sudo apt update
sudo apt install can-utils
To set up a test CAN interface(vcan0) use
modprobe can
modprobe can_raw
modprobe vcan
sudo ip link add dev vcan0 type vcan
sudo ip link set up vcan0
ip link show vcan0
You have a couple of samples here.
VSCP & friends
The VSCP subsystem consist of many system components.
VSCP Daemon
The VSCP daemon is a central piece of software that act as a hub for VSCP based hardware or hardware that abstract as VSCP hardware, You can find the documentation for the VSCP daemon here.
VSCP Works
VSCP works is a tool that make sinteraction with VSCP system components easy. VSCP Works is documented here.
VSCP Helper library
The VSCP helper library is a c/c++ library with common VSCP functionality. It is available for Python to and will be available for PHP and node.js. It is documented here;
More
There is plenty of other tools available in the VSCP subsystem. Check the docs and the downloads.
Other VSCP node-red nodes
There are other node-red parts in development or already available that makes it possible to easily connect to websocket interfaces on remote VSCP daemons/servers or hosts.
Checkout node-red-contrib-vscp-tcp that contains nodes that connect to a remote VSCP tcp/ip host interface and send/receive events.
If you work with CAN, and especially CAN4VSCP, you might find node-red-contrib-socketcan and node-red-contrib-canal useful.
Copyright © 2020 Ake Hedman, Grodans Paradis AB - MIT License
