[Doug]

Looking at the new Hornby Digital range of products we see that they use XPRESSNET as a means of interconnection.

This allows us to add supplementary cab control units around our layout. Or, using XPRESSNET, we can use DCC components from other manufacturers that support the standard (see Compatibility bellow).

XPRESSNET is a high-speed multi-point to multi-point digital network based upon the industry standard RS-485 protocol. DCC systems use XPRESSNET to communicate between its high-speed components such as the command station, hand-helds, tower cabs and its computer interface. XPRESSNET communicates at 62.5 thousand bits per second. It is the highest performance network in widespread DCC use and all its protocols are freely available to both the industry and the hobbyist.

XPRESSNET uses 4 Wires - Two wires are for RS-485 and 2 wires are for 12 volt power and ground. These additional wires provide power to the hand-helds when they are plugged in. Providing power lines with XPRESSNET eliminates the need for batteries in our hand-helds or supplementary transformers for remote cabs

What is RS-485?
An Electronics Industry Alliance (EIA) standard for multipoint communications. It supports several types of connectors, including DB-9, DB-37 and RJ-12. RS-485 is similar to RS-422 but can support more nodes per line because it uses lower-impedance drivers and receivers. Line drivers and receivers are commonly used to exchange data between two or more points (nodes) on a network.

RS485 meets the requirements for a truly multi-point communications network, and the standard specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. With the introduction of "automatic" repeaters and high-impedance drivers / receivers this "limitation" can be extended to hundreds (or even thousands) of nodes on a network. RS485 extends the common mode range for both drivers and receivers in the "tri-state" mode and with power off. Also, RS485 drivers are able to withstand "data collisions" (bus contention) problems and bus fault conditions.

We talk of 2 wires, but XPRESSNET uses 4 Wires. And actually the RJ-12 connectors usually house 6 wires.

What is RJ-12?
RJ-12 jacks and sockets are commonly used in telco installations for phones, modems and security installations. The RJ-12 has a 6-pin connector. Don't confuse it with a computer network connector - the RJ-45 that has a 8-pin connector. The RJ-12 jack will fit into a RJ-45 socket, but the RJ-45 jack will not fit into a RJ-12 socket.

The wires for the 6-pin connector are specified as follows:

And this is how they look on the RJ-12 connector jack:

Connecting an XPRESSNET RJ-12socket to a DIN plug (Lenz) is done as follows:

Compatibility
XPRESSNET / X-Bus which is used by Lenz, Arnold / Lima, ZTC and now Hornby allows these units to be interconnected. Generally it is not advisable to connect a master unit from one manufacturer to a master unit from another, but one can use (for example) Lenz hand cab controllers with the Hornby Elite master unit. In this way, if you are used to one type of controller: Lenz, Roco or ZTC, you can still use the new Hornby system. You should be able to use the Hornby Digital Select unit with a Lenz, ZTC or Arnold master unit. We'll be testing this interconnectivity out as soon as possible.

 

[Gary]

This means that once you have your Hornby Digital Control Unit in place more is possible.

You can use a wireless phone to control your loco:-

http://www.lenz.com/products/xpressnet/xpa.htm

Connect your console to a computer to and link computer software currently available to your console:-

http://www.lenz.com/products/images/li101f.jpg

Connect up to this throttle control software:-

http://www.lenz.com/products/xpressnet/liusb.htm

Use this software on your PC linked to your Hornby Digital control unit:-

http://www.freiwald.com/pages/traincontroller.htm

This all looks interesting.

Happy modelling
Gary

 

[LisaP4]

What they up to now, the 4th rewrite of XpressNet protocols? Oh well I guess they'll get it right eventually. I think they should call it HalfNet, since it's missing half of it's functionality... still. Cut out the middle man and let the decoders comunicate directly with the throttles, ah LocoNet, peace of mind and future proof, and doesn't need constant upgrades and protocol rewrites like that XpressNet junk. Well that's just sunk Hornby's system into the bottom 10% hasn't it.

 

[Doug]

Lets not make this a "My system is better than your system" topic please.

Loconet has got some interesting features. Non-polled nigh-speed network-like system. Loconet is proprietary to Digitrax and is licensed to about 20 other companies.

XpressNET is also widely used - especially by European manufacturers. RS485 protocol does have driver limits, but as mentioned before these limits can be raised by using repeaters and high-impedance drivers. Polling is simply one efficient technique to find out who is currently active on the network and who is not. 32 control devices on a basic system is quite enough for most implementations. XpressNET, according to Lenz is able to be expanded in the future.

I'm not defending one system or another. Both systems have their merits; both systems have limitations. Generally those people that promote one system over the other are generally users of the said system.

More info on Loconet here.

More info on XpressNET here.

 

[Makemineadouble]

QUOTE RS485 meets the requirements for a truly multi-point communications network, and the standard specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. With the introduction of "automatic" repeaters and high-impedance drivers / receivers this "limitation" can be extended to hundreds (or even thousands) of nodes on a network. RS485 extends the common mode range for both drivers and receivers in the "tri-state" mode and with power off. Also, RS485 drivers are able to withstand "data collisions" (bus contention) problems and bus fault conditions.

So as I understand it Xpressnet is currently limited to 32 devices, and this would include
handhelds, boosters,automatic reversing modules, stationary decoders, and the like, so it's quite possible on a large complex layout to reach the capcity of the system ?.

I ask this because I have no practical experience of the Lenz system. Several of our club members are considering a change to DCC. In past discusssions with a large group of Digitrax users at another club, it was always stated that Lenz were not ideally suited to larger walk around layouts. I never fully understood why. I naturally assumed that if you had a cab bus you could simply hang more devices on it as it expanded, as you can with Loconet. Do similar limitations exist with other systems ?.

 

[Doug]

People generally talk of 32 control devices i.e cab controllers. I am not sure if this included other modules.

Stationary decoders take the DCC signals and translate them into electrical pulses to drive points or signals. Reversing modules just switch the polarity of the DCC signals. I don't think these devices limit the scope of XpressNet.

I have 5 DCC controllers: 3 cab controllers and 2 keyboard controllers for the points. Those that have seen the setup can vouch that it is perhaps overkill and only really is all used when there are two or more people on the layout. I could double the amount of controllers and still be well within the 32 device limit.

I have yet to see any club with 32 or more consecutive controllers all active at once.

 

[Rail-Rider]

As a 'digital newbie', I can't help but latch onto the 'number of devices' limitations.

I hate to admit it, but I am quite confused!
My confusion hinges around which 'devices' actually count in this total.
I have an orthodox analogue layout with at least 30 points/turnouts and at least 15 locomotives - always the possibility for more! The layout has four distinctly separate (ananlogue) controllers for the four basic areas of operation (two independent main lines and two different station areas). It seems that I am already beyond the max number of addressable devices for Xpressnet - but am I really?
I'll watch this topic with enormous interest.

 

[LisaP4]

XpressNet doesn't have the necessary functionality to process the data from other devices such as accessory decoders, block detectors and all those other ancillaries mentioned, this is why XpressNet systems need a second comunications BUS (the feedback BUS) running along side XpressNet. This second BUS is limited in it's functionality to that required for the accessory devices, however it is not as limited in it's network size so can therefore handle the many hundreds of devices required without the use of repeaters or any of that nonsense.
Incidently the feedback BUS XpressNet systems use is compatible with LocoNet.
So basicly XpressNet can't handle all the additional devices, but XpressNet systems do include a workaround for the problem.

Doug, ever seen an Ntrack convention? The Network size they run would be impossible with XpressNet.

 

[Makemineadouble]

I've seen massive modular layouts in both Ntrack and HO. Again the only control system has been Digitrax on these layouts. Mainly because South Africa is largley Digitrax due to the poor support for Lenz, and others.
But while I'm talking: with Digitrax each addon to the cab bus be it: booster, reversing module, stationary decoder, PM42, BL16, Handheld & UP5, is connected to loconet or the cabbus system surely Lenz works the same way?.
While I accept that most British layouts at home arn't that big, times are a changing. My
own local branch of the NMRAUK has a large modular layout, yes I'm currently making the switch to American HO. I believe modular layouts must catch on, as they offer so many advantages. The problem then is how to control them. It would seem to me that the only suitable system in DCC (for large layouts) is Digitrax as you simply daisychain the loconet between devices.
I was considering trying Lenz for a smallish shunting layout in my study to save me having to slep controllers from my main layout, but I think I'll go Zephur, as it's compatable with my trottles.

 

[LisaP4]

QUOTE (Makemineadouble @ 4 Jan 2006, 12:17)But while I'm talking: with Digitrax each addon to the cab bus be it: booster, reversing module, stationary decoder, PM42, BL16, Handheld & UP5, is connected to LocoNet or the cabbus system surely Lenz works the same way?.
Uh no.
The main difference is that with LocoNet all devices send data to all other devices, and all devices receive data from all other devices.
With XpressNet all devices send data only to the command station, and only the command station can send data to another device.
XpressNet uses a high data transfer rate because there is no constant updates like there is on LocoNet. Let me put it this way, let's say you have several throttles connected to the system, on one throttle you select loco#1234 and start running it, now here's the differance;
on a LocoNet system as soon as a throttle selects a loco it tells all other throttles that loco#1234 is now in use. So if you try to select loco#1234 on another it won't allow it because it knows that loco is in use already, and the throttle doesn't have to ask because it was told as soon as the other throttle selected that loco.
Put another way this what happens on a LocoNet system;
You select Loco#1234
Throttle tells the system that loco#1234 is in use
If you try to select loco#1234 on another throttle it doesn't have to ask the system because it already knows it's status.
Simple right?

on an XpressNet system it's a bit more complex, there could be up to 31 throttles connected (the command station is the 32nd device), each throttle has it's own ID# (1-31, with the command station being #00) so first the throttle tells the command station it's ID# then asks if it can select loco#1234, the command station then tells the throttle that it is now controlling loco#1234, but none of the other throttles know this because they haven't been told. So if you try to select loco#1234 on another throttle, first the throttle tells the command station it's ID# then asks if it can select loco#1234, the command station then tells the throttle that loco#1234 is currently in use.
Put another way this is what happens on an XpressNet system;
Lets assume you selected the loco on throttle#8, so here's what happens;
You select loco#1234
throttle#8 asks the command station if it can select loco#1234
the command station tells throttle#8 it is now controlling loco#1234
Then if you try to select loco#1234 on another throttle (lets say number 9);
throttle#9 asks the command station if it can select loco#1234
the command station tells throttle#9 that loco#1234 is in use

Now you should be able to see that for the same operation XpressNet is much busier than LocoNet, which is why XpressNet is limited to just 32 devices, anymore than that and the network gets too slow.

So what does this have to do with adding stationary decoders and other devices?

Well if XpressNet gets slow with alot of throttles connected how do you think it will handle having several (dozens? hundreds?) of other devices connected?

Put simply... it can't handle it... it would overload the system and slow it down too much.

So that's why XpressNet systems have a second (feedback) BUS for connecting stationary decoders, block detectors, and other devices to the command station. The XpressNet feedback BUS is purely one directional, the command station sends data to the device through the track, and the device sends data back to the command station through the feedback BUS.
Here's an example of what happens on the two systems when you change a point (we'll say point#01);
on LocoNet
You change point#01 to the left hand route on a throttle
throttle tells point#01 to change to the left hand route
point#01 tells the system it has changed to the left hand route
Now when you look at any throttle you know which direction the point is set

on XpressNet (let's say throttle#8 again)
You change point#01 to the left hand route on throttle#8
throttle#8 tells the command station via XpressNet to change point#01 to the left hand route
the command station tells point#01 via the track to change to the left hand route
point#01 tells the command station via the feed back BUS it has changed to the left hand route
the command station tells throttle#8 via XpressNet that point#01 has changed to the left hand route
the command station asks throttle#1 via XpressNet if it is connected
throttle#1 tells the command station via XpressNet it is connected
the command station tells throttle#1 via XpressNet that point#01 has changed to the left hand route
the command station asks throttle#2 via XpressNet if it is connected
throttle#2 tells the command station via XpressNet it is connected
the command station tells throttle#2 via XpressNet that point#01 has changed to the left hand route
and so on until all throttles have been told that point#01 has changed to the left route and then when you look at any throttle you know which direction the point is set

Hope that explains things.

 

[Makemineadouble]

Thanks for that, I truely believed Xpressnet worked in a similar fashion to Loconet.
Now I appreciate the difference. I assume the feedback bus is daisy chained back to the control station ?. So the weakness with the Lenz cab bus system is it's single direction only.
I still think it's a great pity no standard for cab-bus was developed by the NMRA.

 

[LisaP4]

Ah good, I did write that in something approaching English then, trying to simplify the protocols and write the processes in plain English was begining to drive me mad!

I don't know if I'd call the feedback BUS a daisychain conection, mor like split at ech device, kinda like connect droppers to the track BUS, if you see what I mean?

Standard Cab BUS? LocoNet is the closest we've got, as the XpressNet feedback BUS actually uses part of the LocoNet protocol, so most systems use at least part of LocoNet. I don't know, it's nuts really, I've worked out how to completely eradicate the Cab BUS, but it would do funny things to Railcom equiped decoders, so I think I'll just go scream or something.

 

[Dennis David]

I've been following this thread with interest and I find it analogous to what we face in the software business with the selection of different products. Often I suggest to my clients to look beyond the hype and learn what was the thinking behind the building of the products.

I look at xPressnet and LocoNet as the results of two different philosophies. On the one hand you have the Digitrax (LocoNet) group which is largely driven by the American market and somewhat mimics the highway cruiser where simple but large is one counts.

QUOTE I have yet to see any club with 32 or more consecutive controllers all active at once. I have and while not common it is the market sector that Digitrax is pointing at. So if you understand this everything else starts to make sense.

The Lenz (xPressNet) group is always looking to add the latest bells and whistles hence Lisa's comments on rewrites of the system. To me as long as you can update the firmware this is a non issue and can actually be seen as an advantage. Now without getting into a big argument it's my opinion that while LocoNet may be considered the cleaner system I would not be surprised when new technology is available to xPressNet users sooner than Digitrax users. On the flip side new bess and whistles can result in a less stable system. Digitrax/LocoNet if anything, is a stable system.

The selection of xPressNet doesn't in my opinion weaken or compromise Hornby's DCC products in the slightest. In fact it brings the Lenz world of products to your doorstep.

If you have a large layout with in access of 1/2 dozen cabs operating at the same time take a long hard look at Digitrax if not I would look at the interface(s) available (Display, Buttons) as my first criteria. If you don't like the part that you're holding in your hand then the rest doesn't really matter. On that point and at first glance I think Hornby is on the right track.

 

[Doug]

QUOTE (Rail-Rider @ 4 Jan 2006, 13:26)As a 'digital newbie', I can't help but latch onto the 'number of devices' limitations.

I hate to admit it, but I am quite confused!
...
<{POST_SNAPBACK}>

Rail-Rider, look at the post above yours.

QUOTE (LisaP4 @ 4 Jan 2006, 13:41)...
Doug, ever seen an Ntrack convention? The Network size they run would be impossible with XpressNet.
<{POST_SNAPBACK}>

Lisa, no I have not. Makemineadouble and Dennis seems to though. But be realistic, this is Hornby producing a product for the British Market. Should it aim it's product at clubs with 50 cab controllers running at once using a system that is expensive in terms of license and is generally seen by most users as American? Or should Hornby use a European system that is open source and that IS expandable. Producing a product that works, is cheap and is expandable.

Remember what I said at the start: QUOTE (myself)With the introduction of "automatic" repeaters and high-impedance drivers / receivers this "limitation" can be extended to hundreds (or even thousands) of nodes on a network.

Where basic RS485 may have limits, an XpressNet system repeaters or high-impedance drivers overcomes these.

 

[Dennis David]

QUOTE Should it aim it's product at clubs with 50 cab controllers

Just so people don't get the wrong idea. Hornby's Elite system if it in fact comes with a 4 amp power pack and is not your typical 97lb weakly.

4 amps is a lot of power and can run a large layout run by 1-4 operators each operating a couple of locomotives.

If I didn't have this fixation with all things German

I'd love to get my hands on one.

 

[ChrisE]

QUOTE The Lenz (xPressNet) group is always looking to add the latest bells and whistles hence Lisa's comments on rewrites of the system. To me as long as you can update the firmware this is a non issue and can actually be seen as an advantage.
Another beginners question.

The question is can all xPressNet items be updated as new firmware becomes available?
Are updates distributed via the web, are they free & how are they input into the equipment?
Are updates manufacturer specific or could I, for example use a Lenz update in a Hornby system. I doubt it. If not then the commitment of the manufacturer to providing updates becomes important and the best gauge is past record. What is the past record like for Lenz? Hornby obviously haven't got a past record but I would be suspicious of a non specialist manufacturer really being into things like distributing firmware updates. If no upgrades were forthcoming it would appear that a purchase is likely to be a dead end before very long.

Chris

 

[Doug]

Firmware updates are manufacturer specific.

How you get them depends on the distribution system each manufacturer has in place.

Most of the time, you would have to send a unit in to a service centre for them to 'flash' the EPROM (Erasable Programmable Read Only Memory) chip where the firmware is stored.

I don't know how Lenz is updated, anyone care to reply?

 

[Dennis David]

Not sure about Lenz but most firmware updates I have come across do not need you to bring anything in. Whether it actually updates the EPROM I'm not sure. Examples of this is my camera and my router. Both were downloadable and I was able to upgrade both while they were connected to my computer. My Twin-Center worked the same way as well.

 

[Doug]

Yes, if the device is connected to the PC then it's a breeze. Not all DCC systems are connected to a PC and not all model railway owner even have a PC...

Obviously with more and more people getting on-line, it is logical for a manufacturer to offer updates via the Web.

I can't see anything available online for Lenz products.

 

[Dennis David]

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