G-code interpreter/stepper controller

Hi everybody,

I am in the finishing/debugging stages of a 3 axis stepper controller/
G-Code interpreter.

The missing part is how to handle endswitches.

My assumption is that hitting an endswitch is a catastrophic failure,
and it should never happen; therefore I was going to have the
controller freeze all movements, signal the error (a big red LED) and
let the operator shutdown the system, manually back off the tools,
etc. and restart.

I think that trying to have the tool be "smart" and back off the tool
itself, etc. could possibly lead to damaging the machine and or part
being machined.

Does this make sense ? What is usually done, or expected in such a
case ?

Please let me know what you think is the best way to handle
endswitches, and if you have experience with other systems or
software, let me know how it is done.

BTW, this system has the following features:

- communicates with the host computer through a serial RS232 port
(the host could be a palm pilot :-) ), use of hardware (RTS/CTS)
flow control to ensure dataflow integrity.
- embedded basic G-Code interpreter that supports linear and
circular interpolation in all axis
- extensible to up to 8 axis (through an extension board, to be
designed)
- automatically goes to low-current (holding) setting for a given axis
if that axis has not been active for 100 milliseconds
- active current control through integrated chipset, thus very little
wasted power. Running and holding current are configurable through
separate potentiometer, up to 3 amp per axis (although I have not
tested this much power lacking the needed power supply...)
- each axis can be configured as to what the positive or negative
direction is (to accomodate for different machine configuration)
- configurable "rapid transverse speed" (G00 code)
- configuration settings are saved in permanent memory (eeprom) so
they remain between shutdown/reset.
- up to 10'000 steps per seconds (is this overkill ? my steppers stall
after 900 steps/sec...)

Currently supports unipolar steppers, in full-stepping mode. A bipolar
stepper power board will come next.

All feedback much appreciated, thank you.

bruno