Layout Control Buses that is.
As with any efforts to produce standards, particularly open ones, their has been an attrition of projects in recent years. Layout Control Buses for model railroads are not new, but those that exist now are often based on simplistic and not greatly flexible schemes. Possibly the classic is Dr Bruce Chubbs C/MRI which first appeared in Model Railroader magazine in February of 1985. Based on a simple microprocessor module with an RS-485 or RS-422 interface, connected to a PC, the C/MRI system then uses a series of IO expansion cards to connect to pretty much anything. Updated fairly regularly the Chubb designs are now starting to show their age but are still a viable control system. Information and parts can be found at the JLC Enterprises website.
From the ever industrious MERG group in the UK comes Gordon Hopkins RPC system. Of similar vintage and technology to the Chubb system RPC relies on a series of interconnected interface boards. Having the pleasure of meeting Gordon I can only attest to his keen modelling interest and his designs reflect that. However like the Chubb system it is now getting dated, much of the work on it having been done in the late 90's.
In 2007 or so their again emerged from MERG the CBUS system conceived and developed by Mike Bolton in the UK and Gil Fuchs in California. Based on CAN bus this comparatively new system marks the beginning of the new LCB era. General purpose modules, well connected, using something akin to the producer/consumer model of operation. CBUS has a Yahoo Group as well. The boards are based on PIC controllers with CAN bus. The early boards had some issues with ground bounce and offset, but the later 12V board versions are reported to be somewhat more stable. However the practicve of sharing ground and power for the communications and operation power does detract form the stability of larger layouts. CBUS is a credit to its developers and certainly deserves a look.
OpenLCB arrived on the scene also in 2007 but began life in 2005 when I designed a DCC and accessory system that never saw the light of production. Discussions surrounding this approach stimulated Dr. David Harris and myself to explore further and through our acquaintance with Alex Shepherd in New Zealand we started devising what was at first an object oriented network which transitioned to a producer consumer network as we developed. The principal developers for OpenLCB are myself, David Harris, Bob Jacobsen (of J/MRI) and Alex Shepherd. Their is also an active Yahoo Group. Some hardware has been designed and is in use but much OpenLCB development was done on the Silicon Railway LEDuino (which includes CAN bus, DCC decoder input and rudimentary response signalling, LocoNet interface and the usual serial and USB interfaces) and other Arduino type boards. John Plocher has an Arduino model railway shield.
Don Voss proposed an RS-485 based system (as I recall) which he later moved to CAN bus in 2008 or so. Very little data has been published, but what has can be found linked on the largely outdated NMRAnet website as the S9.5 system.
There have been others, but quite honestly the details are rather vague in my mind right now and I would have to dig back into history. I should also say that I am directly involved with OpenLCB, and I have been a part of the NMRAnet community since essentially before it existed!
Tune in again for some technical discussion very soon.