Just checked code to support subscribing to system events, and have refactored the command echoing program echo.py to use it. The mechanism uses a simple subscribe/publish mechanism to allow "listeners" to subscribe to "events" they are interested in. Events can be broad, like any changes to any engine, or specific; changes to a specific engine (or switch or accessory or train). There is also a "broadcast" channel you can subscribe to which receives all TMCC events the system reads from the LCS Ser2. This is how echo.py now receives its updates.
I threw together a quick and dirty command syntax to query device state and added it into pytrain.py. I've only wired in switches and accessories, but will work on engine and train state next. I have to figure out how to serve this information up to client pytrains. Once I do that, I'll be able to change speeds more gradually by querying an engine's current speed and ramping up/down to the new requested speed. I also want to wire listeners in to the GPIO support so indicated light states can be kept in sync.
I've asked the Lionel folks how to communicate directly with the Base 3 over wifi. This will be a far better mechanism to get the current state of switches, accessories, and power districts, but as far as I know, engine and train states are most likely perceived by interpreting the TMCC command stream (over wifi or serial).
-- Dave
