JMRI Hardware Support: MERGCBUS - Naming
- Event Name and Numbering
- System Names
- Summary of MERGCBUS Events
- Event Naming Specification
- Sending hex strings
This page describes how JMRI uses System Names to access MERGCBUS-attached resources.
Suggestion from Mike Bolton :
His club has adopted the convention of 1 to 9999 for turnouts and 10000 upwards for sensors.
This prevents the possibility of sending sensor events from their CANCABs (9999 max)
but they tie any relevant sensors to the turnout numbers e.g.
TO_1 is +1 and the feedback from this is +10001 for one way and +11001 for the other way.
Using short events (or device numbers) this way makes life very simple with JMRI.
They control the turnouts from the CANCABs as well (also Smartphone throttles), this is reflected in the JMRI panel and works a treat!
Their layout control panel is on a touchscreen monitor connected to a RPi 3B running JMRI, with additional control panels through JMRI Web Server.
Another use of event segmentation could be for modular club layouts,
where various club members building a section at home,
then bringing it together into 1 big super layout.
Module 1 would have events 1,000 > 1,999 Module 2 would have 2,000 > 2,999 etc.
You can invert the polarity of ON and OFF events
- on the initial producer module
- Hardware naming format when entered as a JMRI sensor, turnout or light
- Sensor or turnout settings within JMRI
Start of Day Events
When JMRI is started, it doesn't presume that all sensors, turnouts and lights are active or inactive, they have an unknown status.
The vast majority of MERG module kits can send the current status of their inputs or outputs in response to a SOD event taught to that module.
JMRI can store cross-session information such as Memory Variables and
Block Values ( Train Describer value )
The block will need to be occupied ( active sensor ) on panel startup for a TD to cross-session.
JMRI automatically attempts to create Sensor objects from the traffic that it hears on the MERGCBUS network.
When JMRI hears an ON or OFF event, it creates a Sensor using the corresponding event ID.
This automatically-created sensor defaults to the ON event setting the Sensor ACTIVE and the OFF event setting INACTIVE.
Because events are not intrinsically associated with specific hardware objects, and because people can use event IDs in many ways, this doesn't do what's desired.
Note that there's a MERGCBUS Event Capture Tool.
JMRI internally associates MERGCBUS events with individual JMRI objects (Sensors, Turnouts, Lights, etc.) via the JMRI System Names.
Depending on which MERGCBUS event IDs are used on a particular layout, these system names can get very long, in which case the "user names" are much more useful.
The 1st letter of a sensor, turnout or light system name is the JMRI system letter, generally "M" for MERG connections.
- JMRI sensors use the type letter "S",
MS+123;-345" defines a Sensor that follows the "123 ON" and "345 OFF" events to change state.
- JMRI turnouts use the type letter "T",
- JMRI Lights use the type letter "L", e.g.
|In/Out||Entered as Hardware Address||Meaning||makes System Name||Mask||Equivalent||Min.||Max.||Notes|
|both||18||event 18 On;
event 18 Off
|MT+18||integer||+18;-18||01||65535||SLiM Short Events ASON / ASOF|
|both||+N2E18;-N2E18||Node 2 Event 18; On Event = Active;
Off Event = Inactive
|N 65535 E 65535 ;
N 65535 E 65535
|FLiM Long Events ACON / ACOF|
|both||18;21||event 18 On;
event 21 On
|MT18;21||integer;integer||+18;+21||1 ; 1||65535; 65535|
|both||+18;-21||event 18 On;
|in||200018M07||listen to Events 18 .. 1F||MS200018M07||+ M + hex mask||N/A|
|both||X90002D002E;X91FFFFFFFE||hex CAN frame msg. Active;
hex CAN frame msg. Inactive
|MTX90002D002E;X91FFFFFFFE||hex;hex||N/A||Depends on Opscode||In eg. Thrown sends Long Event N 45 E 46
Closed sends Long Event N 65535 E 65534
|both||+18||event 18 On;
event 18 Off
|both||018||event 18 On;
event 18 Off
|both||200018||Node 2 Event 18; On Event = Active;
Off Event = Inactive
|MS200018||node + (5 digits)||N2E18||100001||6553565535||Current max. that can be entered (JMRI 4.12) is 2147483647|
|both||Node 2 Event 18; On Event = Active;
Off Event = Inactive
|MTN2E18||N + number + E + number||2000018||NOT WORKING
See if able to add / edit logic as mix of 2 top table rows?
65,536 nodes and 65,535 events gives approx 4,294,901,760 event combinations.
65,535 is unrealistic for events within a node but does allow for useful segmentation of event ranges.
MERG module kits can use the whole CBUS range of event numbers, on a reset startup operating in SLiM short event mode.
A MERG CANLED kit can support up to 255 taught events
A Sensor is defined by two
events: The one that sets it ACTIVE, and the one that sets it
If these are mapped to ON and OFF frames with the same event ID number, respectively, only the event ID number need be specified:
The number is decimal.
To increase versatility, it's possible to use different
event ID numbers for the ACTIVE transition (by default, an ON
frame) and INACTIVE transition (by default, an OFF
The ON and OFF coding of MERGCBUS is not entirely consistent
with the event model,
it may be useful to connect the ACTIVE or INACTIVE transition of a JMRI Sensor to an OFF or ON MERGCBUS frame respectively.
Leading "+" and "-" characters can do this. For example,
defines a sensor that goes ACTIVE when an OFF frame with ID number 18 is received,
and goes INACTIVE when an ON frame with ID number 21 is received.
MERGCBUS event numbers (usually) contain a node number in
their most-significant bytes.
You can specify the node number either by using a full 5 decimal digits for the event number itself, preceded by the node number:
or by using the letters "N" and "E" to specify the separate parts:
You can mask off part of the MERGCBUS packet, so any values in
the masked part will still match, using the "M" format
"M" indicates the start of a hexadecimal mask that will be applied, where 1 bits in the mask will be zero bits in the resulting value.
In the example above, "18" through "1F" will match.
This is particularly useful for matching e.g. MERGCBUS short events, where parts of the packet include the node number which should (usually) be ignored.
Hexadcimal numbering is based on the power of 16, using 0-9, then A-F.
MERGCBUS modules communicate by messages with a fixed format: One byte of command and length information, followed optionally by additional data bytes.
In it's most simple form, this is used to send identifiable "events". In turn, events come in two types: "ON" and "OFF", with two forms, short ( SLiM ), and long ( FiLM ).
These are actually sent across a MERGCBUS network in the form of an Opscode, the command information.
There are 255 ops codes, the length of the data string following the Opscode changes depending on which Opscode is used.
There are multiple Opscodes for events, Controlling and programming DCC devices, DCC consisting, Programming nodes with Node Variables, Programming nodes with events, Fast clock and temperature information, RfID reader data, and many more.
Four of these are the common Opscodes for events :
|Ops Code Name
( MERG console log )
|ASON||152||98||Short Event On|
|ASOF||153||99||Short Event Off|
|ACON||144||90||Long Event On|
|ACOF||145||91||Long Event Off|
It's possible to connect a Sensor to arbitrary CAN frames by specifying their data content as a hex string, indicated by "X".
This allows a Sensor or Turnout to disregard any intrinsic meaning to "ON" and "OFF" events, and allows it to respond to, or emit any frame on the layout.
These particular event Opscodes use a Hex string 4 digits long, split into High then Low :
|Entered as Hex||Ops Code||Remaining Hex||Node Decimal||Event Decimal|
Ensure you use the right opscode, eg if you include Nodes for a FiLM address, use ACON instead of ASON.
For system development, you may prefer to view the actual full packet in an application such as MERG CBUS SERVER.
The JMRI MERGCBUS Console Tool can be very useful in seeing what is being sent across the network by the hardware addresses you create.
The console is intended to be a tool to help users monitor packets using short and long events, and may attempt to beautify the output.
The CAN frames can send MERGCBUS opscodes in the hex form of the code you require.
eg, to set up a sensor to send ( DCC emergency stop / Track power on ) opscodes over MERG CBUS,
you could use a hardware address of
|Entered as Hex||Viewed in JMRI MERG CONSOLE||Viewed in CBUS SERVER||Ops Code|
||(RESTP) Request Emergency Stop ALL trains
A MERG CANCMD confirms request with an ESTOP 06 Opscode.
||(TON) Track Power On, normally broadcast from a command station|
All of these Opscode messages are sent with the Standard CAN event frame, however the protocol also allows for access to extended CAN frames.
These frames enable bootloading of modules ( firmware updates ), while future uses of this may also be for local media streaming ( eg. transferring pictures of trains or sound files between modules. )
The extended frames do not interfere with the standard frames, hence modules can be targetted for boatloading by module number, without affecting Standard CAN event frames.
Although module firmware updates are not currently available within JMRI, full support for this is available via 3rd party software ( FCU - FLiM Configuration Utility ), available free for MERG members to download.
Check the MERGCBUS wiki and developers guide for more info and absolute specification.
JMRI Scripting for CAN frames with CanExample.py
MERGCBUS 3rd Party Links See link for the MERGCBUS Developers Guide