The system works like this: there's a 'master' Moteino that's connected to the TMCC serial line or LCS PDI bus. Because I'm using the Radiohead "reliable datagram" protocol, which requires the receiver to acknowledge the message, I wanted the master to only send messages when it reads a TMCC command destined for a remote node on the system. (Otherwise, the system would spend a lot of time waiting for a reply from non-existent nodes).
So, each remote node (that is, installed in an operating car or elsewhere) sends a registration message to the master node when it powers up, which includes the node's TMCC address. The master node keeps a list of the nodes that have registered, and only passes on TMCC commands that are addressed to registered nodes.
The software on the master end is pretty straightforward: read TMCC commands coming in from a TMCC serial line or Legacy PDI interface, and pass those commands on to the registered nodes.
On the receiving end, after the nodes send their registration messages, they wait for TMCC commands addressed to them, and turn on the remote board's SSR when commanded. In this version, the nodes only respond to AUX1 presses, but you could change the program to a more complex control sequence if desired.
Nodes can be programmed as ENGs or ACCs, and have three modes of control:
- Toggle, in which AUX1 toggles the input on and off.
- Momentary, in which the actuator stays on as long as AUX1 is being held down. I use this mode for the Lionel merchandise car.
- Fixed, in which the actuator stays on for a pre-programmed length of time. I use this mode for the MTH caboose, since the caboose motor needs to be activated for about 4 seconds until it closes a microswitch and completes the rest of the cycle on its own.
I think that covers it. If you're interested, the master sketch is here, and the node sketch loaded in the remote cars is here.
As compared to the ERR Mini Commander, the board I've designed is less capable, since it only provides an on-off delivery of track power to the output. But it would be fairly easy to design a more complex Moteino shield that included several outputs, including trials for variable voltage control. The system also requires you to install a master node, to transmit TMCC commands over the radio link. On the other hand the cost of the system is considerably less, and you can easily change the sketch in the nodes to achieve whatever kind of complex behavior you want.
Right now if you're using the LCS PDI connection, the master board has to plug into the end of your PDI bus, since it doesn't pass the PDI commands along. If there's any interest I could design a version with two serial ports that could plug in between LCS modules.
Currently the behavior of the node is fixed when you upload the sketch into the Moteino/Anarduino. It could be possible to make a version that emulates the Mini Commander's "SoftSet," and can be programmed for a new TMCC address or mode with TMCC commands. But since anyone using the system has to be able to program their own nodes, I don't know if that would be worthwhile.
I've used this system for low-cost control of operating cars, but of course you could use it to wirelessly control accessories, switches, lights, etc. with minor modifications to the node design.
