It would appear that nobody here is technical enough and/or owns an oscilloscope to do this experiment.. Try the Marklin Bar and Grill types as well, some of those guys are very technical. Apart from Gregor, I don't know anyone here that this in-depth.

Sam

Sam, I would not say like that.... Rather the opposite....

Haven't touched a real scope myself in 20 years, but several in the group do it for a living...

The free software scope I occasionaly use is limited to 20KHz bandwith so it is of no use here...

Certainly maybe true Juhan... The problem with the B&G guys is they talk about 10% marklin and 90% everything else, including DCC...Which is why I don't go there anymore myself.

Hi all,

I should explain that beyond model trains I have another, rather strange hobby: any new thing I get usually comes under oscilloscope observation until I understand what is going on: handy, toaster, rasor, computer network, and of course model trains. It's fascinating to see how it works and I feel less helpless in our technical world.

My point is, when I add some self-made electric circuit to my layout, could it eventually spoil the mfx signals from the lok ? There is no info on the M* webpages. Only chance is the oscilloscope.

Best regards

Hans Martin

It depends on what you add of course, but as long as you add reasonable things it shouldn't be a problem. There are lots of things added to the electric circuit anyway on a normal layout. The mfx protocol must be robust enough to operate with a lot of different loads, like different decoders, lamps, smoke generators, brake circuits etc. Adding some minor extra load for measurement purposes could not be a problem.

If I had an mfx loco, I would do measurements. But I don't have any mfx loco yet.

I agree Juhan,
in addition, I would expect the central occasionally to send out info ". I know about xxx,yyy and zzz. Are there any others", and sometimes, "would xxx be so kind to send it's attributes?". When a new loco appears, it's serial number will be sent to the central, and an internal (shorter) ID will be assigned and sent to the loco.

/lars

To me it makes sense if not every decoder is allowed to transmit at any time. When there are lots of mfx's present, and most of them are known by the central, it would make sense that the central ask's specific decoders, meaning all others should be silent. So I have the same thinking as Juhan, but for a slightly other reason.

The speed bar on a Mobile Station blinks when 'contact has been lost' it's said. This could be achieved in different ways of course, but the simplest is that it has asked a question and didn't get an answer.

Thinking based on how I think I would have implemented the features we know (or think we know) only (speculations).

/lars

Juhan, many thanks - this is great information ! Do they really talk in such a polite manner, or is cyberworld communication rather like real life: "C'mon guys, need your data - fork it over!" [}:)] ???
Long time ago we had an Deputy Director who sounded exactly that way ... [xx(]

John

Maybe I am missing the point here but does it really matter??
I am just happy that it works.
David

Hi all,

As Rudi I also believe that there is such a highly developed protocol running between the MS and the mfx decoder. I shall not try to resolve all its details with a simple oscilloscope.

However, what I want to understand is much more primitive: how does the mfx decoder send digital signals at all ? The MS, CU, IB etc. send signals via a serial protocol, switching the output voltage between +20 and -20 volts. But how can the mfx decoder do the same, i.e. how can it affect the voltage across the rails ? It has no own power source. In contrast, the MS output works through a brute force power amplifier. Finally you can run locos at this output! Even currents of several amperes have no significant effect on the signal voltage. If the tiny decoder chip would try to send signals this way, it would be fried within seconds.

So, as you see, my problem is still unsolved. Perhaps the decoder sends high frequency signals that cannot pass to the MS power amplifier. Don't know but would like to do.

Regards

Hans Martin

I'm not quite sure about the workings, but I do have an idea about it. I once connected an oscilloscope to an MFX system. What I saw was alternating "old" Motorola protocols and MFX protocols. In between the voltage was held for a while at one of the levels, as far as I remember it was a negative voltage on the studs with respect to the rails. So it's power supply without a digital message. What I think (not sure) is that this power supply between MS protocols enables the decoders to send their messages, superimposed on the power level but with a much smaller voltage. At that time I was not able to go further into it. It was not my own railway and there was not enough time to do further investigation.

Apart from the fun of all this reverse engineering I'm of the opinion that Märklin and/or ESU should release all the details about the protocols. I am always very reluctant to buy a system when the manufacturer wants to keep the principles secret.

Lars, DCC also has the possibility that decoders talk back. (Not yet implemented by any manufacturer)When you read the DCC specs (to be found on www.nmra.org) you can see that it works different. With DCC the power from the central and the boosters is switched off completely in certain intervals and the decoders talk back on stored energy. They don't talk back to the central however, but to the section occupancy detectors. And the message is much simpler. The decoder just says: "Hi, I'm number 47". And so the occupancy detector can report back to the central: "Hi, I'm block 14 and number 47 is here".
So the technique is somewhat similar, but the functionality is completely different.

I can think of two or three ways in which the loco's can communicate back with the system.

In the first two ways, a specific period in time (time slot) must be used in order to allow this uplink (either using a predetermined pattern, or following a system message). Then the two ways are:
- The central unit stops transmitting and listens for a while. Loco's send messages using power stored in a capacitor or so. It's a relatively short message, probably a few sets of bytes will do. They will be faced, of course, with the resistance that other power consumers pose to the rails. If the message is shore enough, and the received at the central is sensitive enough to recognize these (alternating) signals, it will work. If the bytes are send out rather fast (e.g. at a high frequency), than the resistance might be lower.
- The central unit acts as a continuous power source. It then looks carefully at the load (current drawn). Loco's that want to transmit something, do so by a transistor that short-circuits the line shortly in order to send bits (think of an open-collector design). Also here, there is also the load of other power consumers (motors, lights in cars, etc.) but this other loads are relatively stable. And, as we know from the digital braking practices, these other trains have no problems being fed with -15 VDC, especially if this is only for a short time.

A third, rather different way is that no random access time slot is reserved at all, but a separate, independent way is sought for uplink communications. This could be done by having the loco's send their messages on a much higher frequency (that's also what Hans suggests). In fact they would employ RF transmitters, modulating their bytes upon a carrier wave. However, as someone noticed seeing two different protocols alternating on the line, this seems not to be the case. If you would use a simple frequency analyzer (for example FTT - Fast Fourier Transformation = real-time analyses of frequency components) you would be able to see such protocols.

Once we understand the protocol, we could have a follow-up discussion what the new MFX-compatible boosters exactly do (there are several choices/issues there as well!).

Agaim, all of the above is speculative only, not having analysed the protocol myself.

I agree that it is not necessary to understand this (as long as all runs, many of us will be happy), however, it is also nice and challenging to understand.... It could help you solving problems, determining what is allowed when adding things (esp. circuits) to your layout, and may even allow you to build MFX-compatible things yourself.


I cannot agree more. It gives trust to consumers, prevemnts lock-in, allow more freedom and would facilitate allow the entry of third party producers (which might, eventually, be in the interest of M* too). And, for such relatively simple protocols, keeping secrets is not so usefull anyway because with reverse engineering other competitors or third parties will find out anyway. (Assuming to patents on Märklin's side, i did a quick scan on www.espacenet.com but that's no patent search in any way). Some of you might know somthing of the famous IBM System/360 legal fight for access to specifications, very interesting in this context.

Ok, time to stop, I'm drifting off.

best, rudi

I expect one of those patents will be the hinge in the middle of the frame of large steam loks. (BR50, Br85, etc) This is why so many non-Marklin Steam Loks do not handle R1.[:(]

Bad luck - the early bird catches the worm ...

John

Hi nico,

The patents cited by Rudi are all from the years 2002 and 2003. We can't know what M* has invented in 2004 and 2005 because in Germany and most other countries new patents are kept secret for the first 18 months after their application. Therefore we eventually shall not see the full mfx specifications before 2006 or 2007.

So there *** are *** secrets

Hans Martin

Well. Excuse me, Gentlemen - but here comes my dumb question: If MFX is really "The Big One" M is producing so much secrecy about - why didn't it's inventor ESU bother for a patent, then ??????
My only conclusion: perhaps MFX isn't that important at all - except for M ...

John

Hi John,

I think you are right with your statement: for me mfx is of minor importance, I am more interested in overall quality of the models, and up to now I didn't have any problem to remember the ID numebers of my 4 digital loks. Nevertheless it's a challenge to solve this mfx enigma.

Nico,

I should indeed have ben a little bit more precise about patents. You are right: when a patent is granted, it must be published such that anybody else can see whether it affects him. But between application of a patent by the inventor and the time when it is granted there can be up to 7 years (!), at least according to german patent rights. In the first 1 1/2 years of this period the application is secret, then it is published. The owner has the priority on the invention from the date of application, though there is not yet a protection. Protection starts with being granted. Thats a big trick in industrial research: you can never know what your competitor has in mind.

Best regards

Hans Martin

Hi Perz,

Funny, it indeed seems to be the RDS protocol as has been long used to send data with radio programs. I also saw this at the bogobit site (maybe you are involved in this site, I don't know).

This means that M* could use the rather affordable semiconductors already available. For the real freaks, however, it would allow them to decode the signal easily, and maybe even design their own senders

/rudi

I am not involved in the "bogobit" site, but I look there.