Re: STG and Parallel Port

[Paul <paul.corner-at-tesco.net>]

Hi Jon

For a conventional three axis mill, the number of IO used on an STG card is, 
at most, 15 pins. Amp enable & fault, + & - limit, and home switches. This 
leaves plenty of IO for spindle control IF it could be utilised.
Whist it is possible to run a (slightly) hacked bridgeportio to make use of 
the spare IO pins, there is a danger of stgmod and bridgeportio fighting over 
the same pin..
As you have found out, the easiest way to avoid race conditions is to pass 
all IO read/writes through the realtime interface. This has the advantage 
that just one parallel port could be used for all the basics of control. I 
have been running some simulations this afternoon with steppermod and once 
I've done some further tests, will check the changes in to Sourceforge.

Regards, Paul.


On Tuesday 19 Nov 2002 4:43 am, Jon Elson wrote:
> The STG I/O is all taken up with limit and home switches, amp faulta and
> amp enables, etc.
> So, yes, you need to use another parallel port for the auxilliary control.