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.
MERGCBUS is an 'open source' or public domain project hosted by the
Model Electronic Railway Group (MERG), following years of
development by MERG members Mike Bolton and Gil Fuchs.
Their intention was to develop a system for comprehensive layout control based on a general purpose Layout Control Bus (LCB).
They adopted the Gridconnect scheme but with a slight modification.
The header is always HEX bytes and maps directly to the PIC CAN registers, left justified.
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 MERGCBUS.
Module firmware updates can be performed over the MERGCBUS network
JMRI includes support for MERGCBUS events, also DCC over MERGCBUS 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 MERGCBUS network.
MERGCBUS 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 point.
- 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 which provides a high-speed connection for model railroad use
- grid connect
- LAWICEL AB CANUSB and CAN232 adapters.
- MERG CANUSB4
- MERG CANUSB4 A MERGCBUS to USB interface, available in kit form to MERG members.
Other CAN Hardware Interfaces
- The CAN-GC1e Ethernet module can connect to JMRI via MERG Network Interface
- MERG CANPiCap
- The CANPICAP enables direct MERGCBUS connection to a Raspberry Pi via its 40 pin I/O connector, available in kit form to MERG members.
- MERG CANPiWi
- The CANPiWi is based on the Raspberry Pi Zero W, and is an interface between Engine Driver / WiThrottle and MERGCBUS.
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.
- 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 MERGCBUS 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 MERGCBUS use by the IANA ).
- Connection protocol - MERGCBUS
- Connection prefix is normally "M" for MERGCBUS.
- Click Save, and restart.
- 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"
- The MERG menu contains 5 tools:
- Send Frame
- Event Capture Tool
- Event Table
- Node Config Tool
- MERGCBUS Send Frame tool can be used for sending CAN events both manually and repeatedly, great for testing.
JMRI Scripting for CAN frames.