The Revo and standards

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Revo "nice to have" list

Post by dbbotkin » Fri Nov 01, 2013 12:34 am

Hi Lewis,
My overall objective is to build a remote-controlled model railroad with enough positional information about consists to allow them to go from block-to-block automatically, i.e. by a control program.

An Arduino or similar device would be used to monitor the location of equipment based on a number of sensors ranging from RFID to IR beam in complexity. It would be very useful to have a reliable (as in compatible with Revo 802.15.4 code) command syntax and structure for the Arduino to use. I'm currently using XBee transmitters with an Arduino to activate the Crest switch controllers, but a Crest product would be a welcome substitute for the XBee.

The other component would be the interface with the locomotive. It would be nice to have a way to send speed and direction commands to a locomotive and get actual speed as a response, but I realize that this is neither easy nor cheap. An acceptable alternative would be an interface to the Revo controller to "press buttons" electronically from an Arduino. This could allow limited control of speed only.

Any of the above could be implemented through the soon-to-be-released USB dongle and that would be just fine too. The possibility of integrating a layout map of one's railway empire with a Mac/PC control program would certainly add interest to the hobby as well as expand seasonal access.


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You are asking for a Duplex System

Post by MParsons » Fri Nov 01, 2013 4:32 pm

Wow. I'd love to be able to do all that from my computer console.
I think you need to take a look at how Digitrax has fielded hardware to accomplish this to get an idea about the building blocks needed -- and that's just trainside.

A big question is whether the Aristo TE is "duplex" -- does the receiver send back, if "queried" responses and what responses can be queried and replied to. I note that the settings for the receivers are in the transmitters (which is why an engine will change what it is doing when you scroll past a cab on a different transmitter than the one that set the engine, if the second transmitter has different last settings for the engine). With this design I would think that intelligence would not be programmed into receivers to ask settings because they are already available in the transmitter.

A graphic track layout is a major software undertaking. MAJOR. Take a look at what is now available from train control software for various DCC systems to get an idea of what is involved.

I am also doubtful that Aristo will want to reveal the function "calls" (codes) that a transmitter sends to a receiver because that would open the door for competing transmitters. Your code is your intellectual property which protects your investment, and is more important than the hardware.

I'd like to see this happen and might take a swing at some of it myself if the duplex question is answered and if the codes are made available.

Good luck. Keep us informed about solutions you come up with.

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Post by LewisPolk » Fri Nov 01, 2013 4:57 pm

Dear M.Parsons,

Yes, it is the equivalent of a "Duplex" system in that the receiver does transmit back to the transmitter and we do have a speed indicator coming from the loco. Exact speed it hard to determine due to different scales for locos in use, but we do show the relative speed. Our receiver is FCC approved too as it is actually transmitting as well. It transmits 1,000's of times per second back to the transmitter and each packet is tuned to just the one transmitter it's linked to. There is never any interference between different transmitters and receivers, so that is not a limitation.

The real question is how many people want to track loco positions on the layout and is it worth the time on our part to make it happen. At the moment we're hard at work on the base station and the H.O. version, so we can look at other things next year. Actually, sounds comes soon after that and then we can see what is the most in demand.

All the best,
Lewis Polk

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Duplex, but not so complex . . ..

Post by dbbotkin » Fri Nov 01, 2013 5:26 pm

As Lewis wrote, the Revo system does not implement the Zigbee "stack," but the firmware in the transmitter (TX) and receiver (RX) support duplex (at least as that implies "two-way") communication. In fact, there is quite a bit of 802.15.4 traffic among the various Revo devices even when in low-power mode. Both the radio and the microprocessors are capable of doing a lot more than stopping and starting locomotives and operating turnouts.

The key to the system is the assignment of Ch # and GroupID to the RX. After that, the RX will respond to instructions on that Ch# and ID only, but instruction may come from any TX. There is a multi-TX mode setting. I wasn't aware of the engine changing settings on scroll-through as most of my operation involves turnouts, but I will check that out for sure.

As to Digitrax, I have checked them out. They seem to be deeply invested in the HO-indoor-layout market and DCC. That market is huge compared to G-Scale and outdoor operation is about solving a different set of problems.

Radio control and battery operation moves one's G-scale RR to another dimension and one much more prototypical as I see it. For example, building a solar-powered sensor that could report--using RF or other wireless tech--the passage of a consist, is well within the scope of electronic-hobbyist skills. No more wires and no track-signals to worry about.

Your comment on "graphic layout" is absolutely correct if you mean "lifelike," but an abstract representation of the layout as used in the prototype dispatch stations would surely be easier. In fact there are any number of train-simulator programs on Mac's PC's and iPads that provide a proof-of-concept. The BIG problem is the I/O interface, not the layout. That's where the Revo dongle might be headed. Let's hope so!


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Post by dbbotkin » Wed Mar 05, 2014 5:01 pm

Computer control is my goal. Not just "run a train in a loop and stop at the stations" (that's too easy) I want to bang my head against near-prototype operations outside. This means two things: control (move things around) and feedback (know where they are). By 'computer' I mean an Arduino, but any number of alternatives are available, including a PC. In any case, the OS needs to be 'real-time' (RTOS) or close too it. I use 'RC' to mean Revolution Controller or radio control depending on the context.

Control of the turnouts is easier than control of the locomotive as they are just simple commands from the RC, whereas the loco has a number of signals from and to the RC: direction, speed, momentum, etc. My first approach was to hack the RC to allow its buttons to be 'pressed' electrically by the computer. That somehow seemed like cheating, so I and my grandson undertook the task of 'sniffing' the wireless traffic from the RC. That got us to a working, Arduino-powered, turnout controller that would setup a number of 'routes' through the outdoor layout.

No progress on loco-control as yet, mostly due to other distractions.

Feedback in the prototype is by block signals and sensors on the track (old-school) or GPS and radio (modern) but neither scales down easily. There are some IR sensor concepts in pre-production by others, but as these need wiring for power and data, I'm still looking. The middle ground approach I now use was taken from 1950's-60's era hump yards: HD cameras installed so that I can observe the loco movement from my computer screen and control the traffic from a combination of the RC and the Arduino 'route selector'.

The next phase will employ near-field RFID and wireless backhaul to manage block control. The system components from China are cheaper than you'd think. An RFID tag on the engine and another (FRED-like) on the last car should do the trick.

Too much fun!

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