This was my second attempt at controlling a train layout using a PC. Previously, I had started off with a whole heap of circuitry hanging off the parallel port of my PC. Before I had it all finished, I started on an improved(well, different at least) version, this time with a microcontroller based design running off the serial port. The next few pages detail the layout construction, the hardware and software design.
At that time, a large part of the information here was good intentions. I never really got around to building the entire system. A few bits and pieces have been built and tested. I haven't tried putting multiple PICs on the serial port. The PWM part has been tested. The DOS software is up and running. Most of it was a learning exercise and there are a few interface bits I still continue to use.
To see another project along similar lines, have a look at Craig's pages which also deal with a computer controlled layout.