Hardware Support: CAN: Controller Area Networks
There's an emerging trend to develop model-railroad control systems that are based on
standard CAN technology. JMRI provides
support for the development and use of these. Two systems are described below.
OpenLCB is a group of hobbyists and manufacturers who have come together to produce a
future-oriented layout control bus, also called OpenLCB.
JMRI includes basic support for OpenLCB, and more is
being developed along with OpenLCB itself.
The NMRA has decided
to adopt OpenLCB and standardize it as Layout Command
Control (LCC, formerly NMRAnet).
Originally named CBUS by co-founder Gil Fuchs, CBUS is an 'open' protocol for Model
Railway use. The protocol and other useful information is hosted on the MERG public website
(see further support links). CBUS is not owned or controlled by MERG but the co-founders Gil
Fuchs and Mike Bolton are active members. MERG members are able to purchase a range of CBUS
CBUS adopted the Gridconnect scheme but with a slight modification.
The header is always HEX bytes and maps directly to the PIC CAN registers, left
JMRI CBUS support is available for linking JMRI with CBUS,
aimed at users.
Extensive details of the CBUS protocol are available to developers, see the CBUS Wiki hosted on the MERG public website.
There are many MERG module kits available to help running a layout.
Modules can be thought of as
- Consumers eg. a CANSOL solenoid module listening on the CANBUS for a taught event to
throw a turnout
- Producers, eg. a CANACE3 Control Panel Switch sensing module, sending an event when a
physical control panel button is pressed or a toggle switch changed ( multiplexing allows
128 switches on 1 module)
- Or both, eg a CANMIO Servo module listening for taught events to change turnout
positions, then sending its own events on servo start moving, servo mid-point, also sending
an event when completing moving the servo to its final position.
The 3,000+ MERG members are encouraged to to build and design their own modules, and with
MERG being over 50 years old, there is a strong peer review process behind CBUS.
Module firmware updates can be performed over the CBUS network
JMRI includes support for CBUS events, also
DCC over CBUS via a CANCMD kit (a fully featured DCC
Command Station, mini booster and track programmer). This interfaces to JMRI and / or MERG
handheld controllers over a CBUS network.
CBUS events are sent as one-to-many, enabling multiple modules to listen and change status
on 1 single event. eg.
- Event sent from a turnout ( UK - point ) switch monitoring module, sending an "off
event" when the point is thrown, an "on event" when closed.
- This event is received by a Relay module, switching the frog polarity of the physical
- Event also received by a LED module, changing the LEDs on a mimic panel representing
the point position.
- Event also received by JMRI to use in Layout Panels et al.
JMRI can send and receive events for any module node and any module event.
Various CAN-USB adapters are available:
- TCH Technology
- TCH Technology CAN/USB provides a high-speed connection for model railroad use (site
not accessible as of 2019)
- grid connect
LAWICEL AB CANUSB and CAN232 adapters.
CANUSB4 A CBUS to USB interface, available
in kit form to MERG members.
- SPROG DCC Ltd
CANISB A galvanically isolated CBUS to USB
CANable An Open-Source USB to CAN Adapter, these use the
CAN via Lawicell CANUSB System Connection.
Other CAN Hardware Interfaces
The CAN-GC1e Ethernet
module can connect to JMRI via MERG Network Interface
The CANPICAP enables direct CBUS
connection to a Raspberry Pi via its 40 pin I/O connector, available in kit form to MERG
The CANPiWi is based on the Raspberry Pi
Zero W, and is an interface between Engine Driver / WiThrottle and CBUS.
- SPROG DCC Ltd
SPROG DCC Pi-SPROG 3 Plus CBUS DCC Command
Station for direct attachment to a Raspberry-Pi via its 40-pin I/O connector.
SPROG DCC SPROG 3 Plus CBUS DCC Command Station
with integrated USB interface.
JMRI can provide the usual Sensor and Turnout features, once configured for OpenLCB or CBUS "Events".
Example System Naming:
( Event 18 Active / Inactive )
( Node 2 Event 18 Thrown / Closed )
( Event 18 On / Off )
JMRI can connect to CAN networks in several ways:
To use any of the above adapters, select the appropriate device/connection type in the
JMRI Preferences. If using a GridConnect or Lawicel device, be sure to set the appropriate
baud rate under Advanced Preferences.
The TCH Technology adapter does this automatically, so no setting is required.
To connect to a CANUSB4, select "MERG" as system manufacturer, then "CAN via MERG CAN-RS
or CAN-USB" as system connection.
It's also possible to attach via a TCP/IP connection (EtherNet or WiFi). This can either
go to another JMRI instance running e.g. an OpenLCB hub, directly to an IP-CAN adapter, or a
CAN Server. To configure one of these, open the Connections tab in the JMRI Preferences.
- Select as System Manufacturer "OpenLCB"
- For System Connection, select "CAN via GridConnect Network Interface"
- Under settings, enter the IP address and TCP/UDP port for the destination.
OpenLCB CAN Adapters advertise under mDNS/Bonjour, so you can use that to specify the
IP address if JMRI is on the same network segment as your adapter. In that case, put
"openlcbcan.local." (note trailing period!) in the IP address field.
The port number for OpenLCB adapters is 23 by default.
- Set the connection protocol as desired, e.g. "OpenLCB", the Connection Prefix (usually
"M") and Connection Name as needed.
- Click Save, and restart.
MERG via CBUS
- Select as system manufacturer MERG.
- For system connection, select CAN via MERG Network Interface
- Under settings, enter the IP address or hostname of the device with the physical
connection to your CBUS network, eg "192.168.0.5" or "localhost"
The CANPi has a default IP of 192.168.45.1 .
- The TCP port is 5550 ( TCP 5550 is reserved for CBUS use by the IANA ).
- Connection protocol - CBUS
- Connection prefix is normally "M" for CBUS.
- Click Save, and restart.
CBUS Server is a Node.js program, licensed under MIT to allow multiple network
connections to a MERG CANUSB4.
- JMRI provides a basic Monitor tool for watching traffic
on a CAN bus.
- For development, there are CAN Scripting tools for
sending and receiving CAN frames. These can be very useful in testing hardware, etc.
- OpenLCB Send Frame
tool The "Send OpenLCB Frame" tool lets you directly send CAN frames, and certain kinds
of OpenLCB messages, eg "Verify Node" and "Send Request Consumers"
- A CBUS connection provides a number of tools, depending on the features of the
connected hardware, e.g.:
JMRI Scripting for CAN frames.
Third Party info
SPROG DCC Ltd
CBUS is a registered trade mark of Dr Michael Bolton