I spent quite a while on building a system - and finished it last Sunday -, that controls a steppermotor.
Communication with the user is done employing vt100 terminal emulation (application even uses ANSI sequences to generate coloured presentations), which runs on a PC and uses the serial interface of the PC and the 8515.
If anybody is interrested in AVR/serial comms/vt100 emulation pls let me know. I probably can offer timesaving information.
(I use the IAR C and ASM compilers)