JMRI: CBUS Naming

This page discusses how JMRI uses system names to access CBUS-attached resources.

For more on JMRI's CBUS support, see the main CBUS page.

JMRI's Use of Names

JMRI provides an interface to the real layout via internal objects such as Turnouts, Sensors, etc that are closely mapped to corresponding physical devices. This mapping is done via "System Names", which both identify the how to access a particular device, and ar ethe key to looking up the corresponding object in JMRI.

Two examples will perhaps explain this best.

A DCC system uses "accessory decoders" to control e.g. turnouts on the layout. These have addresses like 123, 45, and other small numbers. If you dial the proper number into a handheld throttle, you can control the accessory decoder and hence the turnout on the layout. In JMRI, you access the accessory decoder via a Turnout object, and you provide the needed address as part of the system name when requesting that Turnout. "LT123" is a "T"urnout, accessed via the attached "L"oconet system, using address "123".

Some layout control systems have more complicated addressing. For example, C/MRI addressing involves a node number and a bit number on a specific node. JMRI handles this via a system-specific structure within the system name used to reference C/MRI-connected objects. For example, CT12034 is a "T"urnout on a "C"/MRI system, with bit address "034" on node "12".

CBUS Events

MERG CBUS communicates via 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 indentifiable "events". In turn, events come in two types: "ON" and "OFF".

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