Those changes sound like a great idea John.
Well, here it is, it has gotten about as much functionality as I can cram in. 
For the curious, I attached the current schematic. I added the opto-couplers so the forward and reverse motion outputs are totally isolated. This gives you greater flexibility in using them for various functions.
R2LC Smart Motherboard v1.1 Schematic.pdf
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I updated the previous post with the "final" prototype schematic and pictures and ordered the boards. If they all work out, that will be the production board.
The deed is done! The previous post's prototype is the final product. The boards and parts all arrived today. I sat down at the bench and built one up and put it through it's paces. All the features work as planned, and the motor drive and audio interfaces all function perfectly without upsetting the added lighting output functionality.
Here we go, successful bench test! 
You can see the small proto board on the right, that has the smoke (kinda' dim, it's an 18V bulb), forward and reverse lights. The red, green, and white LED's are the reverse motion, forward motion, and stopped. I'm driving an ERR RS Commander and using the Lionel DCDR to spin the motor.
After hand building this one, you'll probably really want one of these to take the time to build one by hand! It's possible for a 77 year old to build one, so you should be able to successfully compete one if you have a steady hand, desk magnifier, and are a fairly accomplished solderer with a good fine tip iron.
Ordering details?
@cjack posted:Ordering details?
Funny man! I'm not going to hand build these! I think that would certainly make them price-prohibitive! It took about an hour and a half to slap this one together. It's a cool project with lots of added functionality, but it's hard to say how big a market there really is.
I was mulling over the possibility of doing something like I did with the TMCC buffers. Seeing if I could round up enough pre-orders to get a factory build of a batch of them. That would be the only practical method I think. I certainly don't want to front a thousand or two dollars in the hopes that I'd sell enough of them to break even! The smallest practical run in terms of price is probably 100 units, if I had pre-orders for at least half of them, I might shoot the dice and have a run of them done.
Bravo on the successful test run john. Good to hear all is working as per plan.
Rod
The only issue I had was I have the wrong footprint for two of the diodes. So, I'm picking a different part that matches the footprint that I ended up with. Since I have a bunch of boards, I didn't feel like doing another run to fix that, and as it turns out, there is a suitable diode that will fit the pattern that the boards have.
I meant just if the boards are available. I’d get a few.
John, What is your projected price per kit?
Yes, the boards can be made available, I just have to "tweak" the BOM to reflect the one diode change. Somehow it got the wrong size footprint, so I'm just going to change the part to match the existing board. That was the only issue I ran across, not too bad I guess.
Sounds great! Much appreciated!
@Ron_S posted:John, What is your projected price per kit?
I haven't thought about a kit yet. With all the little parts, just packaging them would be a significant job!
I agree John, without a Coke Bottle magnifier I would be lost with the SMT, but figure it is worth a shot to build a few, the benefits this has are worth the try. A BOM and just a board would be ok if you decide not to make kits.
I am in for 5 boards, maybe more.
Believe me, I used the magnifier and my 2.5x reading glasses to full effect. For a couple of the parts, I couldn't see the markings and had to break out the big gun, my 600x magnifier, handy tool. I actually get quite a bit of use out of this for the really tiny stuff. 
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GRJ.....Very good! I'll participate in whatever you decide to do. A few boards and the updated BOM would be OK with me.
Richard
I'm going to get the new and properly sized parts in and build one more to make sure everything fits properly, then I'll make up a package of documentation for download and offer the boards. I'll also make the Gerber files available for anyone that wants to make more after the batch I have is gone. I fudged a couple of parts when I didn't have the exact match in my parts stash, but nothing that affected the operation, a couple of 805 resistors in place of the 603 resistors. However, I'd like to have one built with all the correct parts.
Another point with this board. While it has all sorts of whistles & bells, you can also just populate a minimal board with a couple of the connectors for features you use, and jumper things like the serial data buffer if you aren't loading the serial data too much. That's exactly what I did with a couple of the first prototypes, I just put a few connectors on them and used them in a couple of dummies I was building for a customer. Saved me from waiting for a MB from Lionel. I just needed a convenient way to connect the R2LC to sound, lights, and smoke. You can also add a few components, say to give you a source of 5VDC power. You can also change the regulator and get 12V power from the board, keeping in mind that much of the optional circuitry runs on the 5VDC, so you couldn't do both.
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I've given some thought about how kits might be offered for this build. Keeping in mind that there are lots of fine pitch parts involved, and packaging all these tiny parts so they are identifiable by the builder is going to take some effort. Also, assembling one of these in the full configuration will take good soldering skills and a decent soldering iron suitable for SMT PCB work.
With all that in mind, if I offered kits, I see them running in the $30 range for one kit with all the necessary parts to build the full up configuration. Obviously, that assumes that I have enough interest to order these in at least 100 piece lots to keep the component prices reasonable. Right now the components in quantities of 100 boards run around $10/board. If you order smaller quantities of parts, the price quickly balloons to around $20/board, so you can see my dilemma. Then all those little parts have to be separated and presented in such a way that the builder doesn't get them mixed up, so there's significant labor in packaging each kit to identify all the small parts clearly for construction.
As I had pointed out, you can also build less fully configured configurations, but the task of trying to do kits for all the variations that might exist is way out of the question, at least for me.
Any comments on what would be desirable?
For me it would be like your lighting and YLB kits of just "plug and play". Catering to the 10's that may have a soldering station and soldering skills is foolish.
John,
If you sold the PCB and published the BOM, for me that would work. Between Digikey and other suppliers, the components would be grouped individually, which would allow me to sort and install in order so I didn't get lost.
I have purchased a new magnifier headset, which should allow me to see them as solder.
