Model trains pick up electrical power from the ... The build uses an available Arduino library, so if you want to get into the protocol you’ll have to work through that code.
The recommended input for most Arduino models when powered via non-USB means is 7 to 12V, with a limit of 20V. It's always a good idea to read the specification sheet, though, just to make sure.
Like many of you, we’ve been keeping a close eye on the CH32 family of RISC-V microcontrollers from WCH Electronics. You can get the CH32V003, featuring 2 kB RAM ...