I’ve made some progress over the weekend and now have Python code working to control switches, operate accessories, fire routes and run engines and trains. The code supports both TMCC1 and TMCC2. (Legacy) syntax, and provides a means to specify the command format you want from the command line.
The code can be found on GitHub here:https://github.com/cdswindell/PyLegacy.
TMCC2 provides far more options for engine/train control than does the older TMCC1 syntax. I have about 50% of the TMCC1 engine commands implemented, along with their corresponding TMCC2 counterparts. Of course, this means I’ve only implemented about 10-15% of the TMCC2 engine commands. However, as in TMCC2 land, engine and train commands are the same, except for the first byte of the command, this means I also have a bunch of train commands working!
The CLI layer calls into a set of command generation classes that construct the byte sequences to send to the SER2. This layer is relatively clean and uses a set of Python enums that use the bit patterns associated with each Lionel command to uniquely define them. The address of the entity being controlled can then be logically ORed to this bit string to build the command bytes. Frankly, the hard part is working out a sensible CLI command syntax for the TMCC2 engine/train commands. The Python library ArgParser is definitely my friend!
After I complete the implementation of the TMCC1 and 3-byte TMCC2 engine commands, I will turn to writing unit tests and packaging the code. Then, I’ll move on to connecting physical button presses on my Raspberry Pi to my command architecture.
— Dave
