I've gotten two of the four boards for the drawbot built and sort-of working. The top one is the controller for the pen carrier. It will receive commands over the RS-485 bus (through the big black jack) and drive a servo through the 3-pin header. The six pin header at the top is for in circuit programming the pic16f1823 micro, and the two pin header is for power.
The bottom board is the usb to RS-485 bridge I prototyped. This version just has some indicator LEDs. One for power and two more for data reception and transmission.
Now it's time to work on the software to get the two boards to talk back and forth. Oh happy happy joy joy!!