Latest incarnation of the Phone Throttle Contraption. The phone communicates with the Xbee Controller via bluetooth, a custom app runs on the phone. This is based on previous experiments with an android tablet, you can read about that here- Android, Bluetooth and Xbee

I’m trying to emulate a generic sort of DCC throttle ‘feel’ with this. I have all of the base code written and tested, it’s just a matter of pulling all the parts together. Slowly I’m getting everything working.


Yet another project in the works. This one is intended to leverage my DCC circuit boards into a interrupt driven DCC I/O system for the Arduino Pro Mini. I actually have all of the software done and tested for both the input and output of DCC signals on my Attiny1634 board but I’ve never actually used a real ‘Arduino’. I’ve always built my own boards so this is a learning experience. I’m probably not going to make it compatible with the larger ‘Arduino’ universe, I’ll just optimize it for the Pro Mini. Anyhow, this project is actually number two on the list, the refurbish of my U25B locomotive is first so I can polish off the main widget code base.


Today I got my order of printed circuit boards from Bay Area Circuits. I promptly populated them with components and powered them all up to see how they would do. Everything works! Very nice! Next step is to install these into one of my locomotives and replace all the breadboards with something clean and production quality.

Pictured, in order, is the 8Amp DPDT relay module, it’s used to reverse the direction of the locomotive. It can be triggered either with a logic one or zero, say from an Ardunio, or from an R/C signal via your generic radio control system. (The logic version is shown, the R/C version has an additional chip on the board, you can see the outline).

Second is the DCC output module. It is designed to be driven with a logic signal from a micro-controller such as the Ardunio. Logic input in, attach your choice of battery (or other) power to the input terminals and it provides up to 3Amps of DCC encoded power on the outputs.

Below that is the DCC input module, connect this to any DCC device like the MRC Prodigy or NCE DCC units and it converts the high voltage DCC signal down to what a micro-controller or Ardunio needs.

The last one is my Control Widget Node. This device is a micro controller wired to an industrial strength Xbee Series 1 802.15.4 Wireless Network Module. I use this for both my Control and Slave nodes. It allows high speed data delivered in an organized network infrastructure with a range of about 300 ft. I send both proprietary packets and DCC messages over this in real time. This is the latest PCB design.


I’ve been doing quite a bit of PCB design these days, here is a version of my controller board, the ‘microwidget’. It’s quite compact. I have not had any made yet but I thought it came out really sort of, well, neat. Like art kinda.

All total I have about five or six small circuits for doing control networks- specifically for large scale model trains. DCC input and output, servo control, DC brushed motor control, reversing relays- all via Industrial strength Xbee Network wireless.

I’m also thinking of making an apt-get debian package to install JMRI on a RPi 2 and gitlab for my code. Hmm.

I think I need a Kickstarter 🙂

Here is the Prodigy DCC controlling a servo over my Xbee network. (the video is sped up 200%) This validates the network layer and the speed. However, this is just a raw implementation of the protocol. The DCC message is just sent as fast as possible, regardless if it has changed or not. I don’t want to keep it this fast, there are far far too many Xbee packets flying around. It is ‘thinned’ out a bit because only packets meant for address 8522 are sent to this Xbee but I will need to implement the proper algorithms so that only data that changes is on the network. The client can then maintain the DCC stream on it’s own. Also, with only 128 steps of speed control the precision is lacking controlling the servos smoothly. I’ll need to do some processing of the speed before it’s sent to the servos.

It has a ways to go before it’s a bonafide ‘wireless decoder’ but the basic wireless network works, and that’s the most important, everything else is just more firmware 🙂

So far, I’ve used less about a third of the flash and ram:
Program Memory Usage : 4908 bytes 30.0 % Full
Data Memory Usage : 215 bytes 21.0 % Full




Making good progress on this. What I’ve done here is connect my MRC Prodigy Express DCC system to my Control Widget Platform. The input from the DCC system is run through an optoisolator to get the voltage down to logic levels. I then wrote an IRQ routine to decode and assemble the DCC packets. These get queued, error checked and then passed to the Xbee transmit routine. I pull the DCC destination address (either 1 or 2 bytes) out of the packet and use that as the Xbee destination address.

In the Atmel Studio pic above, you can see the Xbee X-CTU utility displaying a stream of Xbee encoded DCC messages for address 8522. Anything addressed to 8522 flows out over the air and into this particular Xbee which will eventually be on the client controlwidget.

In the logic analyzer pic, you can see I’m blasting these out about every 7ms or so. Pretty fast! This is just for experimental purposes now, just to see how fast I can go over the air. This will eventually change so that the client is doing all the work maintaining the DCC output while the master only sends packets that have changed since the last scan. This will keep the network traffic down.

Next step is to get the client going, decode the packet and apply it to the various things. Servos, Motor Controllers, lights, etc. With a controlwidget as a ‘decoder’ there is not much off limits- drive servos for steam locomotives or large motor controllers for battery locomotives. Or, a little more esoteric, create a ‘router’ that divides the mobile and accessory traffic into different xbee streams? On different channels too. Hmm.

I particularly want to try a sound decoder to see how that works, I wonder if I can use an HO sound decoder. Intercept the motor control data to drive a servo and then pass the data stream to the sound decoder? Hmm. Don’t know. Sounds like a fun experiment however…


I have just started to play with a wonderful new tool, a four channel logic analyzer from

This is a fantastic unit for the price, I can’t tell you how wonderful it is for doing small scale digital h/w design and firmware. I can literally time my interrupt routines, I’m sporting 5us on a dcc decoder INT routine. Sweet. I also found a really bad firmware bottleneck, I love this thing!


Here it is all hooked up to my development system. Atmel Studio 7 drives everything. This is my favorite kind of software development. Right on the metal.


Well, if you can’t beat em join em eh? Ha.

Since I’m putting together a new N scale layout, or at least I’m planning it out right now, I decided I should probably give DCC a go since it’s so popular. So I ordered an inexpensive DCC starter set, the MRC prodigy Express2. I am glad I did. Just on a test loop my little DCC switcher locomotive runs WAY better than it did on DC. And since I like the feel of the MRC Prodigy Express DCC controller (more or less), I figured, why not come up with a way to use that to control, via Xbee, for my G scale stuff too?

So after much scouring and searching via Google, I came up with an input and output circuit for my control widget board.

In the above picture you can see the DCC waveforms and the really simple input side of the circuit. I’ve also got my basic C framework built out and this looks like it will be a fun project if I can ever get the time to work on it!

Anyhow, the basic idea here is read the DCC out of the Prodigy output, transmit that via Xbee and decode it on the other end. Or pass it through, or both. That way you can use any DCC handheld you want to control battery powered locomotives or even live steam ones (via intercepts of DCC commands to servos and relays, etc)

So this should be neat if I can get it to work. Something new to learn anyhow, DCC as a message stream 🙂

I wired up my yellow critter with a control widget, a Turnigy 20A ESC and a 4.8v 2300mah nimh battery pack. Works quite well. I did have to add a relay to reverse the motor but that’s already supported by the software, it’s what I use in my RS3.

A pic from the video, out on the track at Gilbert Virginia.

Just can see the Xbee in the cab. The battery is in the engine compartment along with the Turnigy ESC. The relay to toggle the motor direction is also in the cab but you can’t see it from here.

The development platform for my Dash 9 whenever I get around to it. A close shot of the control board with the Xbee. This is the same control board in the Critter. There is just enough room (I think) in the critter to put in micro servos for the couplers but I have not gotten there yet…

And here is the critter with the handheld controller.