CANopenSocket is a collection of CANopen tools running on Linux with socketCAN interface.
It is based on CANopenNode, which is free and open source CANopen Stack and is included as a git submodule.
CANopen is the internationally standardized (EN 50325-4) (CiA301) CAN-based higher-layer protocol for embedded control system. For more information on CANopen see http://www.can-cia.org/
CANopenSocket may be used as a master or a slave device. However, CANopen itself is not a typical master/slave protocol. It is more like producer/consumer protocol. It is also possible to operate CANopen network without a master. Pre-configured process data (PDO) are transmitted from producers. Each PDO may be consumed by multiple nodes.
Master functionality of CANopenNode contains command line interface with SDO and NMT master commands. With SDO master (or SDO client) it is possible to read or write any variable on any device on the CANopen Network. NMT master can start, stop or reset nodes.
CANopenNode should run on any Linux machine. Examples below was tested on Debian based machines, including Ubuntu, Beaglebone Black and Raspberry PI. It is possible to run tests described below without real CAN interface, because Linux kernel already contains virtual CAN interface.
CANopenSocket consists of two applications: canopend, which runs in background, and canopencomm, command interface for SDO and NMT master.
canopend is an implementation of CANopen device with master functionality. It runs within three threads. Realtime thread processes CANopen SYNC and PDO objects. Mainline thread processes other non time critical objects. Both are nonblocking. Command interface thread is blocking. It accepts commands from socket connection from external application and executes master SDO and NMT tasks.
canopencomm is the other end of the Command interface. It accepts text commands form arguments or from standard input or from file. It sends commands to canopend via socket, line after line. Received result is printed to standard output. It is implementation of the CiA 309 standard.
CANopenSocket is free and open source software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.
We will run two instances of CANopend. First will be basic node with ID=4, second, with nodeID = 3, will have master functionality.
Clone the project from git repository and get submodules:
$ git clone https://github.com/CANopenNode/CANopenSocket.git
$ cd CANopenSocket
$ git submodule init
$ git submodule update
(If you want to work on submodule CANopenNode, you can cd CANopenNode,
and apply git commands directly on it. Initially is in head detached state,
so you have to git checkout master first. Then you can control submodule
separately, for example git remote add {yourName} {url-of-your-git-repository},
and git pull {yourName} {yourbranch})
Prepare CAN virtual (or real) device:
$ sudo modprobe vcan
$ sudo ip link add dev vcan0 type vcan
$ sudo ip link set up vcan0
Run candump from can-utils:
$ sudo apt-get install can-utils
$ candump vcan0
It will show all CAN traffic on vcan0.
Start second terminal, compile and start canopend.
$ cd CANopenSocket/canopend
$ make
$ app/canopend --help
$ app/canopend vcan0 -i 4 -s od4_storage -a od4_storage_auto
You should now see CAN messages on CAN dump terminal. Wait few seconds and press CTRL-C.
vcan0 704 [1] 00 # Bootup message.
vcan0 084 [8] 00 50 01 2F F3 FF FF FF # Emergency message.
vcan0 704 [1] 7F # Heartbeat messages
vcan0 704 [1] 7F # one per second.
Heartbeat messages shows pre-operational state (0x7F). If you follow byte 4 of the Emergency message into [CANopenNode/stack/CO_Emergency.h], CO_EM_errorStatusBits, you will see under 0x2F "CO_EM_NON_VOLATILE_MEMORY", which is generic, critical error with access to non volatile device memory. This byte is CANopenNode specific. You can observe also first two bytes, which shows standard error code (0x5000 - Device Hardware) or third byte, which shows error register. If error register is different than zero, then node is not able to enter operational and PDOs can not be exchanged with it.
You can follow the reason of the problem inside the source code. However, there are missing non-default storage files. Add them and run it again.
$ echo - > od4_storage
$ echo - > od4_storage_auto
$ app/canopend vcan0 -i 4 -s od4_storage -a od4_storage_auto
vcan0 704 [1] 00
vcan0 184 [2] 00 00 # PDO message
vcan0 704 [1] 05
Now there is operational state (0x05) and there shows one PDO on CAN address 0x184. To learn more about PDOs, how to configure communication and mapping parameters and how to use them see other sources of CANopen documentation (For example article of PDO re-mapping procedure in CAN newsletter magazine, June 2016 ).
Start also second instance of canopend (master on nodeID=3) in the same window (canopend terminal). Use default od_storage files and default socket for command interface.
$ # press CTRL-Z
$ bg
$ app/canopend vcan0 -i 3 -c ""
Start third terminal, compile and start canopencomm.
$ cd CANopenSocket/canopencomm
$ make
$ ./canopencomm --help
Play with it and also observe CAN dump terminal. First Heartbeat at index 0x1017, subindex 0, 16-bit integer, on nodeID 4.
$ ./canopencomm [1] 4 read 0x1017 0 i16
$ ./canopencomm [1] 4 write 0x1017 0 i16 5000
In CAN dump you can see some SDO communication. You will notice, that Heartbeats from node 4 are coming in 5 second interval now. You can do the same also for node 3. Now store Object dictionary, so it will preserve variables on next start of the program.
$ ./canopencomm 4 w 0x1010 1 u32 0x65766173
You can read more about Object dictionary variables for this CANopenNode in [canopend/CANopenSocket.html].
If node is operational (started), it can exchange all objects, including PDO, SDO, etc. In pre-operational, PDOs are disabled, SDOs works. In stopped only NMT messages are accepted.
$ ./canopencomm 4 preop
$ ./canopencomm 4 start
$ ./canopencomm 4 stop
$ ./canopencomm 4 r 0x1017 0 i16 # time out
$ ./canopencomm 4 reset communication
$ ./canopencomm 4 reset node
$ ./canopencomm 3 reset node
In canopend terminal you see, that both devices finished. Further commands are not possible. If you set so, last command can also reset computer.
Now you can learn more skills on CANopen from some other sources: books, data sheet of some CANopen device, standard CiA 301(it's free), etc. Then you can enter the big world of CANopen devices.
Accessing real CANopen devices is the same as described above for virtual CAN interface. Some tested USB to CAN interfaces, which are natively integrated into Linux are:
- Simple serial USBtin - Start with:
sudo slcand -f -o -c -s8 /dev/ttyACM0 can0; sudo ip link set up can0 - EMS CPC-USB - Start with:
sudo ip link set up can0 type can bitrate 250000 - PCAN-USB FD - Needs newer Linux kernel, supports CAN flexible data rate.
- You can get the idea of other supported CAN interfaces in Linux kernel source.
- Beaglebone or Paspberry PI or similar has CAN capes available. On RPI worked also the above USB interfaces, but it was necessary to compile the kernel.
With CANopenNode you can also design your own device. There are many very useful and high quality specifications for different device profiles, some of them are public and free to download.
Here we played with virtual CAN interface and result shows as pixels on screen. If you connect real CAN interface to your computer, things may become dangerous. Keep control and safety on your machines!